Diesel Distributor Fuel-Injection Pumps VE - Gnarlodious

Diesel-engine managementDieseldistributor fuel-injection pumpsTechnical Instruction

Published by:© Robert Bosch GmbH, 1999Postfach 30 02 20,D-70442 Stuttgart.Automotive Equipment Business Sector,Department for Automotive Services,Technical Publications (KH/PDI2).Editor-in-Chief:Dipl.-Ing. (FH) Horst Bauer.Editors:Dipl.-Ing. Karl-Heinz Dietsche,Dipl.-Ing. (BA) Jürgen Crepin,Dipl.-Holzw. Folkhart Dinkler,Dipl.-Ing. (FH) Anton Beer.Author:Dr.-Ing. Helmut Tschöke, assisted by theresponsible technical departments ofRobert Bosch GmbH.Presentation:Dipl.-Ing. (FH) Ulrich Adler,Berthold Gauder, Leinfelden-Echterdingen.Translation:Peter Girling.Photographs:Audi AG, Ingolstadt andVolkswagen AG, Wolfsburg.Technical graphics:Bauer & Partner, Stuttgart.Unless otherwise specified, the above persons areemployees of Robert Bosch GmbH, Stuttgart.Reproduction, copying, or translation of thispublication, wholly or in part, only with our previouswritten permission and with source credit.Illustrations, descriptions, schematic drawings, andother particulars only serve to explain and illustratethe text. They are not to be used as the basis fordesign, installation, or delivery conditions. Weassume no responsibility for agreement of thecontents with local laws and regulations.Robert Bosch GmbH is exempt from liability,and reserves the right to makechanges at any time.Printed in Germany.Imprimé en Allemagne.4th Edition, April 1999.English translation of the German edition dated:November 1998.

Dieseldistributor fuel-injection pumps VEThe reasons behind the diesel-poweredvehicle’s continuing success can bereduced to one common denominator:Diesels use considerably less fuel thantheir gasoline-powered counterparts.And in the meantime the diesel haspractically caught up with the gasolineengine when it comes to starting andrunning refinement. Regarding exhaustgasemissions, the diesel engine is justas good as a gasoline engine withcatalytic converter. In some cases, it iseven better. The diesel engine’s emissionsof CO 2 , which is responsible forthe “green-house effect”, are also lowerthan for the gasoline engine, althoughthis is a direct result of the dieselengine’s better fuel economy. It wasalso possible during the past few yearsto considerably lower the particulateemissions which are typical for thediesel engine.The popularity of the high-speed dieselengine in the passenger car though,would have been impossible withoutthe diesel fuel-injection systems fromBosch. The very high level of precisioninherent in the distributor pump meansthat it is possible to precisely meterextremely small injection quantities tothe engine. And thanks to the specialgovernor installed with the VE-pump inpassenger-car applications, the engineresponds immediately to even the finestchange in accelerator-pedal setting. Allpoints which contribute to the sophisticatedhandling qualities of a moderndayautomobile.The Electronic Diesel Control (EDC)also plays a decisive role in the overallimprovement of the diesel-enginedpassenger car.The following pages will deal with thedesign and construction of the VE distributorpump, and how it adapts injectedfuel quantity, start-of-injection, andduration of injection to the differentengine operating conditions.Combustion in the diesel engineThe diesel engine 2Diesel fuel-injection systems:An overviewFields of application 4Technical requirements 4Injection-pump designs 6Mechanically-controlled (governed)axial-piston distributor fuel-injectionpumps VEFuel-injection systems 8Fuel-injection techniques 9Fuel supply and delivery 12Mechanical engine-speed control(governing) 22Injection timing 29Add-on modules andshutoff devices 32Testing and calibration 45Nozzles and nozzle holders 46Electronically-controlled axialpistondistributor fuel-injectionpumps VE-EDC 54Solenoid-valve-controlledaxial-piston distributor fuel-injectionpumps VE-MV 60Start-assist systems 62

Combustionin the dieselengineCombustion in the dieselengine2The diesel engineDiesel combustion principleThe diesel engine is a compressionignition(CI) engine which draws in airand compresses it to a very high level.With its overall efficiency figure, the dieselengine rates as the most efficient combustionengine (CE). Large, slow-runningmodels can have efficiency figures of asmuch as 50% or even more.The resulting low fuel consumption,coupled with the low level of pollutants inthe exhaust gas, all serve to underlinethe diesel engine’s significance.The diesel engine can utilise either the4- or 2-stroke principle. In automotiveapplications though, diesels are practicallyalways of the 4-stroke type (Figs. 1and 2).Working cycle (4-stroke)In the case of 4-stroke diesel engines,gas-exchange valves are used to controlthe gas exchange process by openingand closing the inlet and exhaust ports.Induction strokeDuring the first stroke, the downwardmovement of the piston draws in unthrottledair through the open intake valve.Compression strokeDuring the second stroke, the so-calledcompression stroke, the air trapped in thecylinder is compressed by the pistonwhich is now moving upwards. Compressionratios are between 14:1 and24:1. In the process, the air heats up totemperatures around 900°C. At the endof the compression stroke the nozzle injectsfuel into the heated air at pressuresof up to 2,000 bar.Power strokeFollowing the ignition delay, at the beginningof the third stroke the finely atomizedfuel ignites as a result of auto-ignitionand burns almost completely. Thecylinder charge heats up even furtherand the cylinder pressure increasesagain. The energy released by the ignitionis applied to the piston.The piston is forced downwards and thecombustion energy is transformed intomechanical energy.Exhaust strokeIn the fourth stroke, the piston moves upagain and drives out the burnt gasesthrough the open exhaust valve.A fresh charge of air is then drawn inagain and the working cycle repeated.Combustion chambers,turbocharging andsuperchargingBoth divided and undivided combustionchambers are used in diesel enginesFig. 1Principle of the reciprocating piston engineTDC Top Dead Center, BDC Bottom Dead Center.V h Stroke volume, V C Compression volume,s Piston stroke.TDCV hBDCTDCBDCV CsUMM0001E

(prechamber engines and direct-injectionengines respectively).Direct-injection (DI) engines are more efficientand more economical than theirprechamber counterparts. For this reason,DI engines are used in all commercial-vehiclesand trucks. On the otherhand, due to their lower noise level,prechamber engines are fitted in passengercars where comfort plays a more importantrole than it does in the commercial-vehiclesector. In addition, theprechamber diesel engine features considerablylower toxic emissions (HC andNO X ), and is less costly to produce thanthe DI engine. The fact though that theprechamber engine uses slightly morefuel than the DI engine (10...15 %) isleading to the DI engine coming moreand more to the forefront. Compared tothe gasoline engine, both diesel versionsare more economical especially in thepart-load range.Diesel engines are particularly suitablefor use with exhaust-gas turbochargersor mechanical superchargers. Using anexhaust-gas turbocharger with the dieselengine increases not only the poweryield, and with it the efficiency, but alsoreduces the combustion noise and thetoxic content of the exhaust gas.Diesel-engine exhaustemissionsA variety of different combustion depositsare formed when diesel fuel is burnt.These reaction products are dependentupon engine design, engine power output,and working load.The complete combustion of the fuelleads to major reductions in the formationof toxic substances. Complete combustionis supported by the carefulmatching of the air-fuel mixture, absoluteprecision in the injection process,and optimum air-fuel mixture turbulence.In the first place, water (H 2 O) and carbondioxide (CO 2 ) are generated. And in relativelylow concentrations, the followingsubstances are also produced:– Carbon monoxide (CO),– Unburnt hydrocarbons (HC),– Nitrogen oxides (NO X ),– Sulphur dioxide (SO 2 ) and sulphuricacid (H 2 SO 4 ), as well as– Soot particles.When the engine is cold, the exhaust-gasconstituents which are immediatelynoticeable are the non-oxidized or onlypartly oxidized hydrocarbons which aredirectly visible in the form of white or bluesmoke, and the strongly smelling aldehydes.The dieselengineFig. 24-stroke diesel engine1 Induction stroke, 2 Compression stroke, 3 Power stroke, 4 Exhaust stroke.1 2 3 4UMM0013Y3

Diesel fuelinjectionsystems:An overviewDiesel fuel-injection systems:An overviewFields of applicationDiesel engines are characterized by theirhigh levels of economic efficiency. This isof particular importance in commercialapplications. Diesel engines are employedin a wide range of different versions(Fig. 1 and Table 1), for example as:– The drive for mobile electric generators(up to approx. 10 kW/cylinder),– High-speed engines for passengercars and light commercial vehicles (upto approx. 50 kW/cylinder),– Engines for construction, agricultural,and forestry machinery (up to approx.50 kW/cylinder),– Engines for heavy trucks, buses, andtractors (up to approx. 80 kW/cylinder),– Stationary engines, for instance asused in emergency generating sets (upto approx. 160 kW/cylinder),– Engines for locomotives and ships (upto approx. 1,000 kW/cylinder).Fig. 1TechnicalrequirementsMore and more demands are being madeon the diesel engine’s injection system asa result of the severe regulations governingexhaust and noise emissions, andthe demand for lower fuel-consumption.Basically speaking, depending on theparticular diesel combustion process(direct or indirect injection), in order toensure efficient air/fuel mixture formation,the injection system must inject the fuelinto the combustion chamber at a pressurebetween 350 and 2,050 bar, and theinjected fuel quantity must be meteredwith extreme accuracy. With the dieselengine, load and speed control must takeplace using the injected fuel quantity withoutintake-air throttling taking place.The mechanical (flyweight) governingprinciple for diesel injection systems is in-Overview of the Bosch diesel fuel-injection systemsM, MW, A, P, ZWM, CW in-line injection pumps in order of increasing size; PF single-plunger injectionpumps; VE axial-piston distributor injection pumps; VR radial-piston distributor injection pumps; UPS unitpump system; UIS unit injector system; CR Common Rail system.PFVEVEVEVEZWMZWMVRMWMWVRCWCWMAAMWPFPFMWPPPCRCRCRCRUPSUPSUISUPS4UISUMK1563-1Y

creasingly being superseded by the ElectronicDiesel Control (EDC). In the passenger-carand commercial-vehicle sector,new diesel fuel-injection systems areall EDC-controlled.According to the latest state-of-the-art,it is mainly the high-pressure injectionsystems listed below which are used formotor-vehicle diesel engines.Fields ofapplication,TechnicalrequirementsTable 1Diesel fuel-injection systems: Properties and characteristic dataFuel-injection Injection Engine-related datasystemTypeInjected fuelquantity per strokeMax. nozzlepressurem Mechanicale Electronicem ElectromechanicalMV Solenoid valveDirect injectionIndirect injectionDIIDIPilot injectionPost injectionVENENo. of cylindersMax. speedMax. powerper cylindermm 3 bar min –1 kWIn-line injection pumpsM 111,60 1,550 m, e IDI – 4…6 5,000 1,120A 11,120 1,750 m DI / IDI – 2…12 2,800 1,127MW 11,150 1,100 m DI – 4…8 2,600 1,136P 3000 11,250 1,950 m, e DI – 4…12 2,600 1,145P 7100 11,250 1,200 m, e DI – 4…12 2,500 1,155P 8000 11,250 1,300 m, e DI – 6…12 2,500 1,155P 8500 11,250 1,300 m, e DI – 4…12 2,500 1,155H 1 11,240 1,300 e DI – 6…8 2,400 1,155H 1000 11,250 1,350 e DI – 5…8 2,200 1,170Axial-piston distributor injection pumpsVE 11,120 1,200/350 m DI / IDI – 4…6 4,500 1,125VE…EDC 1 ) 11,170 1,200/350 e, em DI / IDI – 3…6 4,200 1,125VE…MV 11,170 1,400/350 e, MV DI / IDI – 3…6 4,500 1,125Radial-piston distributor injection pumpVR…MV 1,1135 1,700 e, MV DI – 4.6 4,500 1,150Single-plunger injection pumpsPF(R)… 150… 800… m, em DI / IDI – arbitrary 300… 75…18,000 1,500 2,000 1,000UIS 30 2 ) 11,160 1,600 e, MV DI VE 8 3a ) 3,000 1,145UIS 31 2 ) 11,300 1,600 e, MV DI VE 8 3a ) 3,000 1,175UIS 32 2 ) 11,400 1,800 e, MV DI VE 8 3a ) 3,000 1,180UIS-P1 3 ) 111,62 2,050 e, MV DI VE 6 3a ) 5,000 1,125UPS 12 4 ) 11,150 1,600 e, MV DI VE 8 3a ) 2,600 1,135UPS 20 4 ) 11,400 1,800 e, MV DI VE 8 3a ) 2,600 1,180UPS (PF[R]) 13,000 1,400 e, MV DI – 6…20 1,500 1,500Common Rail accumulator injection systemCR 5 ) 1,100 1,350 e, MV DI VE 5a )/NE 3…8 5,000 5b ) 30CR 6 ) 1,400 1,400 e, MV DI VE 6a )/NE 6…16 2,800 2001) EDC Electronic Diesel Control; 2 ) UIS unit injector system for comm. vehs. 3 ) UIS unit injector system forpass. cars; 3a ) With two ECU’s large numbers of cylinders are possible; 4 ) UPS unit pump system for comm.vehs. and buses; 5 ) CR 1st generation for pass. cars and light comm. vehs.; 5a ) Up to 90˚ crankshaft BTDC,freely selectable; 5b ) Up to 5,500 min –1 during overrun; 6 ) CR for comm. vehs., buses, and diesel-poweredlocomotives; 6a ) Up to 30˚ crankshaft BTDC.5

Diesel fuelinjectionsystems:An overview6Injection-pumpdesignsIn-line fuel-injection pumpsAll in-line fuel-injection pumps have aplunger-and-barrel assembly for eachcylinder. As the name implies, this comprisesthe pump barrel and the correspondingplunger. The pump camshaftintegrated in the pump and driven by theengine, forces the pump plunger inthe delivery direction. The plunger is returnedby its spring.The plunger-and-barrel assemblies arearranged in-line, and plunger lift cannotbe varied. In order to permit changes inthe delivery quantity, slots have beenmachined into the plunger, the diagonaledges of which are known as helixes.When the plunger is rotated by the movablecontrol rack, the helixes permit theselection of the required effective stroke.Depending upon the fuel-injection conditions,delivery valves are installed betweenthe pump’s pressure chamber andthe fuel-injection lines. These not onlyprecisely terminate the injection processand prevent secondary injection (dribble)at the nozzle, but also ensure a familyof uniform pump characteristic curves(pump map).PE standard in-line fuel-injection pumpStart of fuel delivery is defined by an inletport which is closed by the plunger’s topedge. The delivery quantity is determinedby the second inlet port being opened bythe helix which is diagonally machinedinto the plunger.The control rack’s setting is determinedby a mechanical (flyweight) governor orby an electric actuator (EDC).Control-sleeve in-line fuel-injectionpumpThe control-sleeve in-line fuel-injectionpump differs from a conventional in-lineinjection pump by having a “controlsleeve” which slides up and down thepump plunger. By way of an actuator shaft,this can vary the plunger lift to port closing,and with it the start of delivery and the startof injection. The control sleeve’s positionis varied as a function of a variety of differentinfluencing variables. Comparedto the standard PE in-line injection pumptherefore, the control-sleeve version featuresan additional degree of freedom.Distributor fuel-injectionpumpsDistributor pumps have a mechanical(flyweight) governor, or an electroniccontrol with integrated timing device. Thedistributor pump has only one plungerand-barrelasembly for all the engine’scylinders.Axial-piston distributor pumpIn the case of the axial-piston distributorpump, fuel is supplied by a vane-typepump. Pressure generation, and distributionto the individual engine cylinders, isthe job of a central piston which runs ona cam plate. For one revolution of thedriveshaft, the piston performs as manystrokes as there are engine cylinders.The rotating-reciprocating movement isimparted to the plunger by the cams onthe underside of the cam plate which rideon the rollers of the roller ring.On the conventional VE axial-piston distributorpump with mechanical (flyweight)governor, or electronically controlledactuator, a control collar defines theeffective stroke and with it the injectedfuel quantity. The pump’s start of deliverycan be adjusted by the roller ring (timingdevice). On the conventional solenoidvalve-controlledaxial-piston distributorpump, instead of a control collar anelectronically controlled high-pressuresolenoid valve controls the injected fuelquantity. The open and closed-loop controlsignals are processed in two ECU’s.Speed is controlled by appropriate triggeringof the actuator.Radial-piston distributor pumpIn the case of the radial-piston distributorpump, fuel is supplied by a vane-typepump. A radial-piston pump with cam ringand two to four radial pistons is responsible

for generation of the high pressure and forfuel delivery. The injected fuel quantity ismetered by a high-pressure solenoidvalve. The timing device rotates the camring in order to adjust the start of delivery.As is the case with the solenoid-valvecontrolledaxial-piston pump, all open andclosed-loop control signals are processedin two ECU’s. Speed is controlled byappropriate triggering of the actuator.Single-plunger fuel-injectionpumpsPF single-plunger pumpsPF single-plunger injection pumps areused for small engines, diesel locomotives,marine engines, and constructionmachinery. They have no camshaft oftheir own, although they correspond tothe PE in-line injection pumps regardingtheir method of operation. In the case oflarge engines, the mechanical-hydraulicgovernor or electronic controller is attacheddirectly to the engine block. Thefuel-quantity adjustment as defined bythe governor (or controller) is transferredby a rack integrated in the engine.The actuating cams for the individual PFsingle-plunger pumps are located on theengine camshaft. This means that injectiontiming cannot be implemented byrotating the camshaft. Here, by adjustingan intermediate element (for instance, arocker between camshaft and roller tappet)an advance angle of several angulardegrees can be obtained.Single-plunger injection pumps are alsosuitable for operation with viscous heavyoils.Unit-injector system (UIS)With the unit-injector system, injectionpump and injection nozzle form a unit.One of these units is installed in the engine’scylinder head for each engine cylinder,and driven directly by a tappet orindirectly from the engine’s camshaftthrough a valve lifter.Compared with in-line and distributor injectionpumps, considerably higher injectionpressures (up to 2050 bar) have becomepossible due to the omission of thehigh-pressure lines. Such high injectionpressures coupled with the electronicmap-based control of duration of injection(or injected fuel quantity), mean that aconsiderable reduction of the diesel engine’stoxic emissions has become possibletogether with good shaping of therate-of-discharge curve.Electronic control concepts permit a varietyof additional functions.Unit-pump system (UPS)The principle of the UPS unit-pump systemis the same as that of the UIS unitinjector. It is a modular high-pressure injectionsystem. Similar to the UIS, theUPS system features one UPS singleplungerinjection pump for each enginecylinder. Each UP pump is driven by theengine’s camshaft. Connection to the nozzle-and-holderassembly is through ashort high-pressure delivery line preciselymatched to the pump-system components.Electronic map-based control of the startof injection and injection duration (inother words, of injected fuel quantity)leads to a pronounced reduction in thediesel engine’s toxic emissions. The useof a high-speed electronically triggeredsolenoid valve enables the characteristicof the individual injection process,the so-called rate-of-discharge curve, tobe precisely defined.Accumulator injectionsystemCommon-Rail system (CR)Pressure generation and the actual injectionprocess have been decoupled fromeach other in the Common Rail accumulatorinjection system. The injection pressureis generated independent of enginespeed and injected fuel quantity, and isstored, ready for each injection process,in the rail (fuel accumulator). The start ofinjection and the injected fuel quantityare calculated in the ECU and, via the injectionunit, implemented at each cylinderthrough a triggered solenoid valve.Injection-pumpdesigns7

Axial-pistondistributorpumpsMechanically-controlled(governed) axial-piston distributorfuel-Injection pumps VEFuel-injectionsystemsAssignmentsThe fuel-injection system is responsiblefor supplying the diesel engine with fuel.To do so, the injection pump generatesthe pressure required for fuel injection.The fuel under pressure is forced throughthe high-pressure fuel-injection tubing tothe injection nozzle which then injects itinto the combustion chamber.The fuel-injection system (Fig. 1) includesthe following components andassemblies: The fuel tank, the fuel filter,the fuel-supply pump, the injectionnozzles, the high-pressure injectiontubing, the governor, and the timingdevice (if required).The combustion processes in the dieselengine depend to a large degree uponthe quantity of fuel which is injected andupon the method of introducing this fuelto the combustion chamber.The most important criteria in this respectare the fuel-injection timing and theduration of injection, the fuel’s distributionin the combustion chamber, the momentin time when combustion starts, theamount of fuel metered to the engine perdegree crankshaft, and the total injectedfuel quantity in accordance with theengine loading. The optimum interplay ofall these parameters is decisive for thefaultless functioning of the diesel engineand of the fuel-injection system.Fig. 1Fuel-injection system with mechanically-controlled (governed) distributor injection pump1 Fuel tank, 2 Fuel filter, 3 Distributor fuel-injection pump, 4 Nozzle holder with nozzle, 5 Fuel return line,6 Sheathed-element glow plug (GSK) 7 Battery, 8 Glow-plug and starter switch, 9 Glow control unit (GZS).154263,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,9788UMK1199Y

TypesThe increasing demands placed uponthe diesel fuel-injection system made itnecessary to continually develop andimprove the fuel-injection pump.Following systems comply with thepresent state-of-the-art:– In-line fuel-injection pump (PE) withmechanical (flyweight) governor orElectronic Diesel Control (EDC) and, ifrequired, attached timing device,– Control-sleeve in-line fuel-injectionpump (PE), with Electronic DieselControl (EDC) and infinitely variablestart of delivery (without attachedtiming device),– Single-plunger fuel-injection pump (PF),– Distributor fuel-injection pump (VE)with mechanical (flyweight) governoror Electronic Diesel Control (EDC).With integral timing device,– Radial-piston distributor injectionpump (VR),– Common Rail accumulator injectionsystem (CRS),– Unit-injector system (UIS),– Unit-pump system (UPS).Fuel-injectiontechniquesFields of applicationSmall high-speed diesel enginesdemand a lightweight and compact fuelinjectioninstallation. The VE distributorfuel-injection pump (Fig. 2) fulfills thesestipulations by combining– Fuel-supply pump,– High-pressure pump,– Governor, and– Timing device,in a small, compact unit. The dieselengine’s rated speed, its power output,and its configuration determine theparameters for the particular distributorpump.Distributor pumps are used in passengercars, commercial vehicles, agriculturaltractors and stationary engines.Fig. 2: VE distributor pump fitted to a 4-cylinderdiesel engineFuel-injectiontechniquesUMK0318Y9

holders. If the distributor pump is alsoequipped with a mechanical fuel shutoffdevice this is mounted in the governorcover.The governor assembly comprising theflyweights and the control sleeve isdriven by the drive shaft (gear withrubber damper) via a gear pair. Thegovernor linkage mechanism whichconsists of the control, starting, andtensioning levers, can pivot in thehousing.The governor shifts the position of thecontrol collar on the pump plunger. Onthe governor mechanism’s top side isthe governor spring which engageswith the external control lever throughthe control-lever shaft which is held inbearings in the governor cover.The control lever is used to controlpump function. The governor coverforms the top of the distributor pump, andalso contains the full-load adjustingscrew, the overflow restriction or theoverflow valve, and the engine-speedadjusting screw. The hydraulic injectiontiming device is located at the bottom ofthe pump at right angles to the pump’slongitudinal axis. Its operation is influencedby the pump’s internal pressurewhich in turn is defined by the vane-typefuel-supply pump and by the pressure-regulatingvalve. The timing deviceis closed off by a cover on each sideof the pump (Fig. 4).Fuel-injectiontechniquesFig. 4The subassemblies and their configuration1 Pressure-control valve, 2 Governor assembly, 3 Overflow restriction,4 Distributor head with high-pressure pump, 5 Vane-type fuel-supply pump, 6 Timing device,7 Cam plate, 8 Electromagnetic shutoff valve.3281456 7UMK0319Y11

Axial-pistondistributorpumpsPump driveThe distributor injection pump is drivenby the diesel engine through a specialdrive unit. For 4-stroke engines, thepump is driven at exactly half the enginecrankshaft speed, in other wordsat camshaft speed. The VE pump mustbe positively driven so that it’s driveshaft is synchronized to the engine’spiston movement.This positive drive is implemented bymeans of either toothed belts, pinion,gear wheel or chain. Distributor pumpsare available for clockwise and forcounter-clockwise rotation, whereby theinjection sequence differs dependingupon the direction of rotation.The fuel outlets though are alwayssupplied with fuel in their geometricsequence, and are identified with theletters A, B, C etc. to avoid confusionwith the engine-cylinder numbering.Distributor pumps are suitable for engineswith up to max. 6 cylinders.Fig. 1Fuel supply anddeliveryConsidering an injection system withdistributor injection pump, fuel supplyand delivery is divided into low-pressureand high-pressure delivery (Fig. 1).Low-pressure stageLow-pressure deliveryThe low-pressure stage of a distributorpumpfuel-injection installation comprisesthe fuel tank, fuel lines, fuel filter,vane-type fuel-supply pump, pressurecontrolvalve, and overflow restriction.The vane-type fuel-supply pump drawsfuel from the fuel tank. It delivers avirtually constant flow of fuel perrevolution to the interior of the injectionpump. A pressure-control valve is fittedto ensure that a defined injection-pumpinterior pressure is maintained as afunction of supply-pump speed. Usingthis valve, it is possible to set a definedpressure for a given speed. The pump’s7rs‚ƒ„‘’“”¡¢£°±²ÀÁÐFuel supply and delivery in a distributor-pump fuel-injection system1 Fuel tank, 2 Fuel line (suction pressure), 3 Fuel filter, 4 Distributor injection pump,5 High-pressure fuel-injection line, 6 Injection nozzle, 7 Fuel-return line (pressureless),8 Sheathed-element glow plug.123456128,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,UMK0316Y

interior pressure then increases inproportion to the speed (in other words,the higher the pump speed the higherthe pump interior pressure). Some of thefuel flows through the pressureregulatingvalve and returns to thesuction side. Some fuel also flowsthrough the overflow restriction andback to the fuel tank in order to providecooling and self-venting for theinjection pump (Fig. 2). An overflow valvecan be fitted instead of the overflowrestriction.Fuel-line configurationFor the injection pump to function efficientlyit is necessary that its highpressurestage is continually providedwith pressurized fuel which is free ofvapor bubbles. Normally, in the case ofpassenger cars and light commercialvehicles, the difference in height betweenthe fuel tank and the fuel-injectionequipment is negligible. Furthermore, thefuel lines are not too long and they haveadequate internal diameters. As a result,the vane-type supply pump in theinjection pump is powerful enough to drawthe fuel out of the fuel tank and to build upsufficient pressure in the interior of the injectionpump.In those cases in which the differencein height between fuel tank and injectionpump is excessive and (or) the fuel linebetween tank and pump is too long, apre-supply pump must be installed. Thisovercomes the resistances in the fuelline and the fuel filter. Gravity-feedtanks are mainly used on stationaryengines.Fuel tankThe fuel tank must be of noncorrodingmaterial, and must remain free of leaksat double the operating pressure and inany case at 0.3 bar. Suitable openings orsafety valves must be provided, orsimilar measures taken, in order topermit excess pressure to escape ofits own accord. Fuel must not leak pastthe filler cap or through pressurecompensationdevices. This applieswhen the vehicle is subjected to minormechanical shocks, as well as whenFuel-injectiontechniquesFig. 2Interaction of the fuel-supply pump, pressure-control valve, and overflow restriction1 Drive shaft, 2 Pressure-control valve, 3 Eccentric ring, 4 Support ring, 5 Governor drive,6 Drive-shaft dogs, 7 Overflow restriction, 8 Pump housing.1 2 3 4 5 6 7 8UMK0321Y13

Axial-pistondistributorpumpscornering, and when standing or drivingon an incline. The fuel tank and theengine must be so far apart from eachother that in case of an accident there isno danger of fire. In addition, specialregulations concerning the height of thefuel tank and its protective shieldingapply to vehicles with open cabins, aswell as to tractors and busesVane-type fuel-supply pump for lowpressuredelivery1 Inlet, 2 Outlet.Fuel linesAs an alternative to steel pipes, flameinhibiting,steel-braid-armored flexiblefuel lines can be used for the lowpressurestage. These must be routed toensure that they cannot be damagedmechanically, and fuel which has drippedor evaporated must not be able toaccumulate nor must it be able to ignite.2Fuel filterThe injection pump’s high-pressurestage and the injection nozzle aremanufactured with accuracies of severalthousandths of a millimeter. As a result,1Fig. 3: Vane-type fuel-supply pump with impelleron the drive shaftUMK0324YFig. 414UMK0320Y

contaminants in the fuel can lead tomalfunctions, and inefficient filtering cancause damage to the pump components,delivery valves, and injectornozzles. This means that a fuel filterspecifically aligned to the requirementsof the fuel-injection system is absolutelyimperative if trouble-free operation anda long service life are to be achieved.Fuel can contain water in bound form(emulsion) or unbound form (e.g.,condensation due to temperaturechanges). If this water gets into theinjection pump, corrosion damage can bethe result. Distributor pumps musttherefore be equipped with a fuel filterincorporating a water accumulator fromwhich the water must be drained off atregular intervals. The increasingpopularity of the diesel engine in thepassenger car has led to thedevelopment of an automatic waterwarningdevice which indicates bymeans of a warning lamp when watermust be drained.Vane-type fuel supply pumpThe vane-type pump (Figs. 3 and 4) islocated around the injection pump’s driveshaft. Its impeller is concentric with theshaft and connected to it with a Woodruffkey and runs inside an eccentric ringmounted in the pump housing.When the drive shaft rotates, centrifugalFig. 5Pressure-control valveforce pushes the impeller’s four vanesoutward against the inside of theeccentric ring. The fuel between thevanes’ undersides and the impellerserves to support the outward movementof the vanes.The fuel enters through theinlet passage and a kidney-shapedrecess in the pump’s housing, and fillsthe space formed by the impeller, thevane, and the inside of the eccentric ring.The rotary motion causes the fuelbetween adjacent vanes to be forced intothe upper (outlet) kidney-shaped recessand through a passage into the interior ofthe pump. At the same time, some of thefuel flows through a second passage tothe pressure-control valve.Pressure-control valveThe pressure-control valve (Fig. 5) isconnected through a passage to theupper (outlet) kidney-shaped recess, andis mounted in the immediate vicinity ofthe fuel-supply pump. It is a springloadedspool-type valve with which thepump’s internal pressure can be variedas a function of the quantity of fuel beingdelivered. If fuel pressure increasesbeyond a given value, the valve spoolopens the return passage so that the fuelcan flow back to the supply pump’ssuction side. If the fuel pressure is toolow, the return passage is closed by thespring.Fig. 6Overflow restrictionFuel-injectiontechniquesUMK0322YUMK0323Y15

Axial-pistondistributorpumpsThe spring’s initial tension can beadjusted to set the valve openingpressure.Overflow restrictionThe overflow restriction (Figure 6) isscrewed into the injection pump’sgovernor cover and connected to thepump’s interior. It permits a variableamount of fuel to return to the fuel tankthrough a narrow passage. For thisfuel, the restriction represents a flowresistance that assists in maintainingthe pressure inside the injection pump.Being as inside the pump a preciselydefined pressure is required as a functionof pump speed, the overflow restrictionand the flow-control valve are preciselymatched to each other.Fig. 7High-pressure stageThe fuel pressure needed for fuelinjection is generated in the injectionpump’s high-pressure stage. Thepressurized fuel then travels to theinjection nozzles through the deliveryvalves and the fuel-injection tubing.Distributor-plunger driveThe rotary movement of the drive shaftis transferred to the distributor plungervia a coupling unit (Fig. 7), whereby thedogs on cam plate and drive shaftengage with the recesses in the yoke,which is located between the end of thedrive shaft and the cam plate. The camplate is forced against the roller ring bya spring, and when it rotates the camlobes riding on the ring’s rollers convertthe purely rotational movement of thedrive shaft into a rotating-reciprocatingmovement of the cam plate.The distributor plunger is held in the camplate by its cylindrical fitting piece and islocked into position relative to the camPump assembly for generation and delivery of high pressure in the distributor-pump interior16UMK0326Y

Pump assembly with distributor headGenerates the high pressure and distributes the fuel to the respective fuel injector.1 Yoke, 2 Roller ring, 3 Cam plate, 4 Distributor-plunger foot, 5 Distributor plunger, 6 Link element,7 Control collar, 8 Distributor-head flange, 9 Delivery-valve holder, 10 Plunger-return spring,4...8 Distributor head.Fuel-injectiontechniques1 2 34 5 6 7 10 8 9UMK0327Yplate by a pin. The distributor plungeris forced upwards to its TDC positionby the cams on the cam plate, and thetwo symmetrically arranged plungerreturnsprings force it back down again toits BDC position.The plunger-return springs abut at oneend against the distributor head and atthe other their force is directed to theplunger through a link element. Thesesprings also prevent the cam platejumping off the rollers during harshacceleration. The lengths of the returnsprings are carefully matched to eachother so that the plunger is not displacedfrom its centered position (Fig. 8).Fig. 8Cam plates and cam contoursThe cam plate and its cam contour influencethe fuel-injection pressure andthe injection duration, whereby camstroke and plunger-lift velocity are thedecisive criteria. Considering the differentcombustion-chamber configurations andcombustion systems used in the variousengine types, it becomes imperative thatthe fuel-injection factors are individuallytailored to each other. For this reason, aspecial cam-plate surface is generated foreach engine type and machined into thecam-plate face. This defined cam plate isthen assembled in the correspondingdistributor pump. Since the cam-platesurface is specific to a given engine type,the cam plates are not interchangeablebetween the different VE-pump variants.17

Axial-pistondistributorpumpsDistributor headThe distributor plunger, the distributorheadbushing and the control collar areso precisely fitted (lapped) into thedistributor head (Fig. 8), that they sealeven at very high pressures. Smallleakage losses are nevertheless unavoidable,as well as being desirable forplunger lubrication. For this reason, thedistributor head is only to be replacedas a complete assembly, and never theplunger, control collar, or distributorflange alone.Fuel meteringThe fuel delivery from a fuel-injectionpump is a dynamic process comprisingseveral stroke phases (Fig. 9). Thepressure required for the actual fuelinjection is generated by the high-pressurepump. The distributor plunger’sstroke and delivery phases (Fig. 10)show the metering of fuel to an enginecylinder. For a 4-cylinder engine thedistributor plunger rotates through 90°for a stroke from BDC to TDC and backagain. In the case of a 6-cylinder engine,the plunger must have completedthese movements within 60° of plungerrotation.As the distributor plunger moves fromTDC to BDC, fuel flows through the openinlet passage and into the high-pressurechamber above the plunger. At BDC, theplunger’s rotating movement then closesthe inlet passage and opens the distributorslot for a given outlet port (Fig. 10a).The plunger now reverses its directionof movement and moves upwards, theworking stroke begins. The pressurethat builds up in the high-pressurechamber above the plunger and in theoutlet-port passage suffices to open thedelivery valve in question and the fuelis forced through the high-pressure lineto the injector nozzle (Fig. 10b). Theworking stroke is completed as soon asthe plunger’s transverse cutoff borereaches the control edge of the controlcollar and pressure collapses. Fromthis point on, no more fuel is deliveredto the injector and the delivery valvecloses the high-pressure line.Fig. 9: The cam plate rotates against the roller ring,whereby its cam track follows the rollers causingit to lift (for TDC) and drop back again (for BDC)18UMK0328Y

Fig. 10Distributor plunger with stroke and delivery phasesFuel-injectiontechniquesa Inlet passagecloses.At BDC, the meteringslot (1) closes the inletpassage, and thedistributor slot (2) opensthe outlet port.UT12b Fuel delivery.During the plungerstroke towards TDC(working stroke),the plunger pressurizesthe fuel in the highpressurechamber (3).The fuel travels throughthe outlet-port passage (4)to the injection nozzle.UT4 23c End of delivery.Fuel delivery ceasesas soon as thecontrol collar (5)opens the transversecutoff bore (6).UT OT5 6d Entry of fuel.Shortly before TDC,the inlet passageis opened. Duringthe plunger’s returnstroke to BDC,the high-pressurechamber is filled withfuel and the transversecutoff bore is closedagain. The outlet-portpassage is alsoclosed at this point.UT OTOT = TDCUT = BDCUMK0329Y19

Axial-pistondistributorpumpsDuring the plunger’s continued movementto TDC, fuel returns through thecutoff bore to the pump interior. Duringthis phase, the inlet passage is openedagain for the plunger’s next working cycle(Fig. 10c).During the plunger’s return stroke, itstransverse cutoff bore is closed by theplunger’s rotating stroke movement,and the high-pressure chamber above theplunger is again filled with fuel throughthe open inlet passage (Fig. 10d).Delivery valveThe delivery valve closes off the highpressureline from the pump. It has thejob of relieving the pressure in the lineby removing a defined volume of fuelupon completion of the delivery phase.This ensures precise closing of the injectionnozzle at the end of the injectionprocess. At the same time, stablepressure conditions between injectionpulses are created in the high-pressurelines, regardless of the quantity of fuelbeing injected at a particular time.Fig. 11The delivery valve is a plunger-typevalve. It is opened by the injection pressureand closed by its return spring.Between the plunger’s individual deliverystrokes for a given cylinder, thedelivery valve in question remainsclosed. This separates the high-pressureline and the distributor head’soutlet-port passage. During delivery,the pressure generated in the highpressurechamber above the plungercauses the delivery valve to open. Fuelthen flows via longitudinal slots, into aring-shaped groove and through thedelivery-valve holder, the high-pressureline and the nozzle holder to the injectionnozzle.As soon as delivery ceases (transversecutoff bore opened), the pressure inthe high-pressure chamber above theplunger and in the highpressure linesdrops to that of the pump interior, and thedelivery-valve spring together with thestatic pressure in the line force the delivery-valveplunger back onto itsseat again (Fig. 11).Distributor head with high-pressure chamber1 Control collar, 2 Distributor head, 3 Distributor plunger, 4 Delivery-valve holder, 5 Delivery-valve.1234520UMK0335Y

Delivery valve with return-flowrestrictionPrecise pressure relief in the lines isnecessary at the end of injection. Thisthough generates pressure waveswhich are reflected at the deliveryvalve. These cause the delivery valveto open again, or cause vacuum phasesin the high-pressure line. These processesresult in post-injection of fuel withattendant increases in exhaust emissionsor cavitation and wear in the injectionline or at the nozzle. To prevent suchharmful reflections, the delivery valve isprovided with a restriction bore which isonly effective in the direction of returnflow. This return-flow restriction comprisesa valve plate and a pressurespring so arranged that the restrictionis ineffective in the delivery direction,whereas in the return direction dampingcomes into effect (Fig. 12).Constant-pressure valveWith high-speed direct-injection (Dl)engines, it is often the case that theFig. 12Delivery valve with return-flow restriction1 Delivery-valve holder, 2 Return-flow restriction,3 Delivery-valve spring, 4 Valve holder,5 Piston shaft, 6 Retraction piston.“retraction volume” resulting from theretraction piston on the delivery-valveplunger does not suffice to reliablyprevent cavitation, secondary injection,and combustion-gas blowback intothe nozzle-and-holder assembly. Here,constant-pressure valves are fittedwhich relieve the high-pressure system(injection line and nozzle-and-holderassembly) by means of a single-actingnon-return valve which can be set to agiven pressure, e.g., 60 bar (Fig. 13).High-pressure linesThe pressure lines installed in the fuelinjectionsystem have been matchedprecisely to the rate-of-discharge curveand must not be tampered with duringservice and repair work. The high-pressurelines connect the injection pumpto the injection nozzles and are routedso that they have no sharp bends. Inautomotive applications, the highpressurelines are normally secured withspecial clamps at specific intervals, andare made of seamless steel tubing.Fig. 13Constant-pressure valve1 Delivery-valve holder, 2 Filler piece with springlocator, 3 Delivery-valve spring, 4 Delivery-valveplunger, 5 Constant-pressure valve, 6 Springseat, 7 Valve spring (constant-pressure valve),8 Setting sleeve, 9 Valve holder, 10 Shims.Fuel-injectiontechniques1121023345654UMK1183Y9876UMK1184Y21

Axial-pistondistributorpumpsMechanical enginespeedcontrol(governing)ApplicationThe driveability of a diesel-poweredvehicle can be said to be satisfactorywhen its engine immediately respondsto driver inputs from the acceleratorpedal. Apart from this, upon driving offthe engine must not tend to stall. Theengine must respond to acceleratorpedalchanges by accelerating or deceleratingsmoothly and without hesitation.On the flat, or on a constant gradient,with the accelerator pedal held in a givenposition, the vehicle speed should alsoremain constant. When the pedal isreleased the engine must brake thevehicle. On the diesel engine, it is theinjection pump’s governor that ensuresthat these stipulations are complied with.The governor assembly comprises theFig. 1mechanical (flyweight) governor and thelever assembly. It is a sensitive controldevice which determines the positionof the control collar, thereby definingthe delivery stroke and with it the injectedfuel quantity. It is possible to adaptthe governor’s response to setpointchanges by varying the design of thelever assembly (Fig. 1).Governor functionsThe basic function of all governors isthe limitation of the engine’s maximumspeed. Depending upon type, the governoris also responsible for keepingcertain engine speeds constant, suchas idle speed, or the minimum andmaximum engine speeds of a stipulatedengine-speed range, or of the completespeed range, between idle and maximumspeed. The different governortypes are a direct result of the variety ofgovernor assignments (Fig. 2):– Low-idle-speed governing: The dieselengine’s low-idle speed is controlled bythe injection-pump governor.Distributor injection pump with governor assembly, comprising flyweight governor and leverassembly22UMK0343Y

– Maximum-speed governing: With theaccelerator pedal fully depressed, themaximum full-load speed must notincrease to more than high idle speed(maximum speed) when the load isremoved. Here, the governor respondsby shifting the control collar back towardsthe “Stop” position, and the supply of fuelto the engine is reduced.– Intermediate-speed governing: Variable-speedgovernors incorporate intermediate-speedgoverning. Withincertain limits, these governors can alsomaintain the engine speeds betweenidle and maximum constant. Thismeans that depending upon load, theengine speed n varies inside the engine’spower range only between n VT(a given speed on the full-load curve)and n LT (with no load on the engine).Other control functions are performedby the governor in addition to its governingresponsibilities:– Releasing or blocking of the extra fuelrequired for starting,– Changing the full-load delivery as aFig. 2Governor characteristicsa Minimum-maximum-speed governor,b Variable-speed governor.1 Start quantity, 2 Full-load delivery,3 Torque control (positive),4 Full-load speed regulation, 5 Idle.abmmControl-collar travelmmControl-collar travel5512 3 412 3 40 Engine speed min –1UMK0344Efunction of engine speed (torque control).In some cases, add-on modules arenecessary for these extra assignments.Speed-control (governing) accuracyThe parameter used as the measure forthe governor’s accuracy in controllingengine speed when load is removed isthe so-called speed droop (P-degree).This is the engine-speed increase,expressed as a percentage, that occurswhen the diesel engine’s load is removedwith the control-lever (accelerator)position unchanged. Within thespeed-control range, the increase inengine speed is not to exceed a givenfigure. This is stipulated as the high idlespeed. This is the engine speed whichresults when the diesel engine, startingat its maximum speed under full load, isrelieved of all load. The speed increase isproportional to the change in load,and increases along with it.δ = n lo – n von voor expressed in %:δ = n lo – n vo . 100%n vowhereδ = Speed droopn lo = High idle (maximum) speed= Maximum full-load speedn voThe required speed droop depends onengine application. For instance, on anengine used to power an electrical generatorset, a small speed droop is requiredso that load changes result inonly minor speed changes and thereforeminimal frequency changes. On theother hand, for automotive applicationslarge speed droops are preferablebecause these result in more stablecontrol in case of only slight loadchanges (acceleration or deceleration)and lead to better driveability. A low-valuespeed droop would lead to rough, jerkingoperation when the load changes.Mechanicalgoverning23

Axial-pistondistributorpumpsVariable-speed governorThe variable-speed governor controlsall engine speeds between start andhigh idle (maximum). The variable-speedgovernor also controls the idle speed andthe maximum full-load speed, as well asthe engine-speed range in between.Here, any engine speed can be selectedby the accelerator pedal and, dependingupon the speed droop, maintainedpractically constant (Fig. 4).This is necessary for instance whenancillary units (winches, fire-fightingpumps, cranes etc.) are mounted on thevehicle. The variable-speed governoris also often fitted in commercial andagricultural vehicles (tractors andcombine harvesters).Design and constructionThe governor assembly is driven by thedrive shaft and comprises the flyweighthousing complete with flyweights.The governor assembly is attached tothe governor shaft which is fixed in thegovernor housing, and is free to rotatearound it. When the flyweights rotatethey pivot outwards due to centrifugalforce and their radial movement isconverted to an axial movement of thesliding sleeve. The sliding-sleeve traveland the force developed by the sleeveinfluence the governor lever assembly.This comprises the starting lever, tensioninglever, and adjusting lever (notshown). The interaction of spring forcesand sliding-sleeve force defines thesetting of the governor lever assembly,variations of which are transferred tothe control collar and result in adjustmentsto the injected fuel quantity.StartingWith the engine at standstill, the flyweightsand the sliding sleeve are in theirinitial position (Fig. 3a). The startinglever has been pushed to the startposition by the starting spring and haspivoted around its fulcrum M 2 . At thesame time the control collar on the distributorplunger has been shifted to itsFig. 3Variable-speed governor. Start and idle positionsa Start position, b Idle position.1 Flyweights, 2 Sliding sleeve, 3 Tensioning lever, 4 Starting lever, 5 Starting spring, 6 Control collar,7 Distributor-plunger cutoff port, 8 Distributor plunger, 9 Idle-speed adjusting screw, 10 Engine-speedcontrol lever, 11 Control lever, 12 Control-lever shaft, 13 Governor spring, 14 Retaining pin, 15 Idle spring.a Starting-spring travel, c Idle-spring travel, h 1 max. working stroke (start); h 2 min. working stroke (idle):M 2 fulcrum for 4 and 5.ab12913 14 c1011151a31245M 2M 267248 h 1 h 2UMK0346Y

start-quantity position by the ball pin onthe starting lever. This means thatwhen the engine is cranked thedistributor plunger must travel through acomplete working stroke (= maximumdelivery quantity) before the cutoff boreis opened and delivery ceases. Thusthe start quantity (= maximum deliveryquantity) is automatically made availablewhen the engine is cranked.The adjusting lever is held in the pumphousing so that it can rotate. It can beshifted by the fuel-delivery adjustingscrew (not shown in Figure 3). Similarly,the start lever and tensioning lever arealso able to rotate in the adjusting lever.A ball pin which engages in the controlcollar is attached to the underside ofthe start lever, and the start spring toits upper section. The idle spring isattached to a retaining pin at the topend of the tensioning lever. Alsoattached to this pin is the governorspring. The connection to the enginespeedcontrol lever is through a lever andthe control-lever shaft.It only needs a very low speed for thesliding sleeve to shift against the softstart spring by the amount a. In theprocess, the start lever pivots aroundfulcrum M 2 and the start quantity is automaticallyreduced to the idle quantity.Low-idle-speed controlWith the engine running, and theaccelerator pedal released, the enginespeedcontrol lever shifts to the idleposition (Figure 3b) up against the idlespeedadjusting screw. The idle speedis selected so that the engine still runsreliably and smoothly when unloaded oronly slightly loaded. The actual controlis by means of the idle spring on theretaining pin which counteracts the forcegenerated by the flyweights.This balance of forces determines thesliding-sleeve’s position relative to thedistributor plunger’s cutoff bore, andwith it the working stroke. At speedsabove idle, the spring has beencompressed by the amount c and is nolonger effective. Using the special idlespring attached to the governor housing,Characteristic curves of the variablespeedgovernorA: Start position of the control collar,S: Engine starts with start quantity,S–L: Start quantity reduces to idle quantity,L: Idle speed n LN following engine start-up(no-load),L–B: Engine acceleration phase after shifting theengine-speed control lever from idle to a givenrequired speed n c ,B–B': The control collar remains briefly in thefull-load position and causes a rapid increasein engine speed,B'–C: Control collar moves back (less injectedfuel quantity, higher engine speed). In accordancewith the speed droop, the vehicle maintainsthe required speed or speed n c in the part-loadrange,E: Engine speed n LT , after removal of loadfrom the engine with the position of the enginespeedcontrol-lever remaining unchanged.mmA SControl-collar travel sB B' Full loadL E No-load0 500 1,000 1,500 2,000 min –1n A n C n LT n VHnLOEngine speed nthis means that idle speed can beadjusted independent of the acceleratorpedalsetting, and can be increased ordecreased as a function of temperatureor load.Operation under loadDuring actual operation, dependingupon the required engine speed orvehicle speed, the engine-speed controllever is in a given position within itspivot range. This is stipulated by thedriver through a given setting of theaccelerator pedal. At engine speedsabove idle, start spring and idle springhave been compressed completely andhave no further effect on governoraction. This is taken over by thegovernor spring.CUMK0348EFig. 4Mechanicalgoverning25

Axial-pistondistributorpumpsExample (Fig. 5):Using the accelerator pedal, the driversets the engine-speed control lever to aspecific position corresponding to adesired (higher) speed. As a result ofthis adjustment of the control-leverposition, the governor spring is tensionedby a given amount, with theresult that the governor-spring forceexceeds the centrifugal force of theflyweights and causes the start lever andthe tensioning lever to pivot aroundfulcrum M 2 . Due to the mechanicaltransmission ratio designed into thesystem, the control collar shifts in the“Full-load” direction. As a result, thedelivery quantity is increased and theengine speed rises. This causes theflyweights to generate more force which,through the sliding sleeve, opposes thegovernor-spring force.The control collar remains in the “Fullload”position until a torque balanceoccurs. If the engine speed continues toincrease, the flyweights separate evenfurther, the sliding-sleeve force prevails,Fig. 5and as a result the start and tensioninglevers pivot around M 2 and push thecontrol collar in the “Stop” direction sothat the control port is opened sooner.It is possible to reduce the deliveryquantity to “zero” which ensures thatengine-speed limitation takes place. Thismeans that during operation, and as longas the engine is not overloaded, everyposition of the engine-speed control leveris allocated to a specific speed rangebetween full-load and zero. Theresult is that within the limits set by itsspeed droop, the governor maintains thedesired speed (Fig. 4).If the load increases to such an extent(for instance on a gradient) that eventhough the control collar is in the fullloadposition the engine speed continuesto drop, this indicates that it isimpossible to increase fuel delivery anyfurther. This means that the engine isoverloaded and the driver must changedown to a lower gear.Fig. 5: Variable-speed governor, operation under loada Governor function with increasing engine speed, b with falling engine speed.1 Flyweights, 2 Engine-speed control lever, 3 Idle-speed adjusting screw, 4 Governor spring,5 Idle spring, 6 Start lever, 7 Tensioning lever, 8 Tensioning-lever stop, 9 Starting spring,10 Control collar, 11 Adjusting screw for high idle (maximum) speed, 12 Sliding sleeve,13 Distributor-plunger cutoff bore, 14 Distributor plunger.h 1 Working stroke, idle, h 2 Working stroke, full-load, M 2 fulcrum for 6 and 7.ab3245111167891226M 2M 21013h 1 14 h 2UMK0349Y

Overrun (engine braking)During downhill operation the engine is“driven” by the vehicle, and enginespeed tends to increase. This causesthe flyweights to move outwards so thatthe sliding sleeve presses against thetensioning and start levers. Both leverschange their position and push thecontrol collar in the direction of less fueldelivery until a reduced fuel-deliveryfigure is reached which corresponds tothe new loading level. At the extreme,the delivery figure is zero. Basically,with the variable-speed governor, thisprocess applies for all settings of theengine-speed control lever, when theengine load or engine speed changesto such an extent that the controlcollar shifts to either its full-load or stopposition.Fig. 6Characteristic curves of the minimummaximum-speedgovernor with idle springand intermediate springa Starting-spring range,b Range of starting and idle spring,d Intermediate-spring range,f Governor-spring range.mmControl-collar travel sa b d Uncontrolled fFull loadNo-loadMinimum-maximum-speedgovernorThe minimum-maximum-speed governorcontrols (governs) only the idle(minimum) speed and the maximumspeed. The speed range between thesepoints is directly controlled by the acceleratorpedal (Fig. 6).Design and constructionThe governor assembly with flyweights,and the lever configuration, are comparablewith those of the variable-speedgovernor already dealt with. The maindifference lies in the governor spring andits installation. It is in the form ofa compression spring and is held in aguide element. Tensioning lever andgovernor spring are connected by aretaining pin.StartingWith the engine at standstill, the flyweightsare also stationary and thesliding sleeve is in its initial position. Thisenables the starting spring to push theflyweights to their inner position throughthe starting lever and the sliding sleeve.On the distributor plunger, the controlcollar is in the start-quantity position.Idle controlOnce the engine is running and theaccelerator pedal has been released, theengine-speed control lever is pulled backto the idle position by its return spring.The centrifugal force generated by theflyweights increases along with enginespeed (Fig. 7a) and the inner flyweightlegs push the sliding sleeve up againstthe start lever. The idle spring on thetensioning lever is responsible for thecontrolling action. The control collar isshifted in the direction of “less delivery”by the pivoting action of the start lever, itsposition being determined by interactionbetween centrifugal force and springforce.MechanicalgoverningEngine speed n min –1UMK0351E27

Axial-pistondistributorpumpsOperation under loadIf the driver depresses the acceleratorpedal, the engine-speed control leveris pivoted through a given angle. Thestarting and idle springs are no longereffective and the intermediate springcomes into effect. The intermediatespring on the minimum-maximum-speedgovernor provides a “soft” transition tothe uncontrolled range. If the enginespeedcontrol lever is pressed evenfurther in the full-load direction, theintermediate spring is compressed untilthe tensioning lever abuts against theretaining pin (Fig. 7b). The intermediatespring is now ineffective and theuncontrolled range has been entered.This uncontrolled range is a function ofthe governor-spring pretension, and inthis range the spring can be regarded asa solid element. The accelerator-pedalposition (engine-speed control lever) isnow transferred directly through thegovernor lever mechanism to the controlcollar, which means that the injectedFig. 7fuel quantity is directly determined by theaccelerator pedal. To accelerate, or climba hill, the driver must “give gas”, or easeoff on the accelerator if less enginepower is needed.If engine load is now reduced, withthe engine-speed control lever positionunchanged, engine speed increaseswithout an increase in fuel delivery. Theflyweights’ centrifugal force also increasesand pushes the sliding sleeveeven harder against the start andtensioning levers. Full-load speed controldoes not set in, at or near the engine’srated speed, until the governor-springpre-tension has been overcome by theeffect of the sliding-sleeve force.If the engine is relieved of all load, speedincreases to the high idle speed, and theengine is thus protected against overrevving.Passenger cars are usually equippedwith a combination of variable-speedgovernor and minimum-maximum-speedgovernor.Minimum-maximum-speed governora Idle setting, b Full-load setting.1 Flyweights, 2 Engine-speed control lever, 3 Idle-speed adjusting screw, 4 Governor spring,5 Intermediate spring, 6 Retaining pin, 7 Idle spring, 8 Start lever, 9 Tensioning lever, 10 Tensioning-leverstop, 11 Starting spring, 12 Control collar, 13 Full-load speed control, 14 Sliding sleeve, 15 Distributorplunger cutoff bore, 16 Distributor plunger.a Start and idle-spring travel, b Intermediate-spring travel, h 1 Idle working stroke, h 2 Full-load workingstroke, M 2 fulcrum for 8 and 9.ab32114ab5613147891011M 2M 212161528h 1h 2UMK0352Y

Injection timingIn order to compensate for the injectionlag and the ignition lag, as enginespeed increases the timing deviceadvances the distributor pump’s startof delivery referred to the engine’scrankshaft. Example (Fig. 1):Start of delivery (FB) takes place afterthe inlet port is closed. The high pressurethen builds up in the pump which,as soon as the nozzle-opening pressurehas been reached leads to thestart of injection (SB). The periodbetween FB and SB is referred to as theinjection lag (SV). The increasingcompression of the air-fuel mixture in thecombustion chamber then initiates theignition (VB). The period between SBand VB is the ignition lag (ZV). As soonas the cutoff port is opened again thepump pressure collapses (end of pumpdelivery), and the nozzle needle closesagain (end of injection, SE). This isfollowed by the end of combustion (VE).AssignmentDuring the fuel-delivery process, theinjection nozzle is opened by a pressurewave which propagates in the highpressureline at the speed of sound.Basically speaking, the time required forthis process is independent of enginespeed, although with increasing enginespeed the crankshaft angle betweenstart of delivery and start of injectionalso increases. This must becompensated for by advancing thestart of delivery. The pressure wave’spropagation time is determined by thelength of the high-pressure line andthe speed of sound which is approx.1,500 m/s in diesel fuel. The intervalrepresented by this propagation time istermed the injection lag. In other words,the start of injection lags behind the startof delivery. This phenomena is thereason for the injector opening later(referred to the engine’s piston position)at higher engine speeds than at lowengine speeds. Following injection, theinjected fuel needs a certain time inFig. 1Curve of a working stroke at full loadand at low speed (not drawn to scale).FB Start of delivery, SB Start of injection,SV Injection lag, VB Start of combustion,ZV Ignition lag, SE End of injection,VE End of combustion.1 Combustion pressure,2 Compression pressure,UT BDC,OT TDC.Plunger position hbarZVSVCombustion-chamberpressurePump high pressure pNozzle-needle lift n DRate of injection QBDC TDC BDCbar4003002001000mm0.30.20.10mm 3°cms642SVVBSBFBTDCTDCSEVEFB SB SE0-16 -12 -8 -4-2 TDC2 4 8 12 16°cms BTDC°cms ATDCDegrees camshaft12UMK0357EInjectiontiming29

Axial-pistondistributorpumpsorder to atomize and mix with the air toform an ignitable mixture.This is termed the air-fuel mixturepreparation time and is independent ofengine speed. In a diesel engine, thetime required between start of injectionand start of combustion is termed theignition lag.The ignition lag is influenced by thediesel fuel’s ignition quality (defined bythe Cetane Number), the compressionratio, the intake-air temperature, andthe quality of fuel atomization. As arule, the ignition lag is in the orderof 1 millisecond. This means that presuminga constant start of injection, thecrankshaft angle between start ofinjection and start of combustionincreases along with increasing enginespeed. The result is that combustion canno longer start at the correct point(referred to the engine-piston position).Being as the diesel engine’s mostefficient combustion and power can onlybe developed at a given crankshaft orFig. 2piston position, this means that the injectionpump’s start of delivery must beadvanced along with increasing enginespeed in order to compensate for theoverall delay caused by ignition lagand injection lag. This start-of-deliveryadvance is carried out by the enginespeed-dependenttiming device.Timing deviceDistributor injection pump with timing device1 Roller ring, 2 Roller-ring rollers, 3 Sliding block, 4 Pin, 5 Timing-device piston,6 Cam plate, 7 Distributor plunger.Design and constructionThe hydraulically controlled timing deviceis located in the bottom of thedistributor pump’s housing, at rightangles to the pump’s longitudinal axis(Fig. 2), whereby its piston is free tomove in the pump housing. The housingis closed with a cover on each side.There is a passage in one end of thetiming device plunger through which thefuel can enter, while at the other end theplunger is held by a compression spring.The piston is connected to the roller ring301 2 3 4 5 6 7UMK0354Y

through a sliding block and a pin so thatpiston movement can be converted torotational movement of the roller ring.Method of operationThe timing-device piston is held in itsinitial position by the timing-device spring(Fig. 3a). During operation, the pressurecontrolvalve regulates the fuel pressureinside the pump so that it is proportionalto engine speed. As a result, the enginespeed-dependentfuel pressure is appliedto the end of the timing-devicepiston opposite to the spring.As from about 300 min –1 , the fuelpressure inside the pump overcomes thespring preload and shifts the timingdevicepiston to the left and with it thesliding block and the pin which engagesin the roller ring (Fig. 3b). The roller ringis rotated by movement of the pin, andthe relative position of the roller ring tothe cam plate changes with the resultthat the rollers lift the rotating cam plateat an earlier moment in time. In otherwords, the roller ring has been rotatedthrough a defined angle with respectto the cam plate and the distributorplunger. Normally, the maximum angleis 12 degrees camshaft (24 degreescrankshaft).Fig. 3Timing device, method of operationa Initial position,b Operating position.1 Pump housing, 2 Roller ring,3 Roller-ring rollers, 4 Pin,5 Passage in timing-device piston,6 Cover, 7 Timing-device piston,8 Sliding block, 9 Timing-device spring.ba987123456InjectiontimingUMK0355Y31

Axial-pistondistributorpumpsAdd-on modulesand shutoff devicesApplicationThe distributor injection pump is builtaccording to modular constructionprinciples, and can be equipped with avariety of supplementary (add-on) units(Fig. 1). These enable the implementationof a wide range of adaptationpossibilities with regard to optimizationof engine torque, power output, fueleconomy, and exhaust-gas composition.The overview provides a summary ofFig. 1Distributor injection pump with add-on modules1 Cold-start accelerator,2 Manifold-pressure compensator.the add-on modules and their effectsupon the diesel engine. The schematic(Fig. 2) shows the interaction of thebasic distributor pump and the variousadd-on modules.Torque controlTorque control is defined as varyingfuel delivery as a function of enginespeed in order to match it to theengine’s fuel-requirement characteristic.If there are special stipulations withregard to the full-load characteristic(optimization of exhaust-gas composition,of torque characteristic curve, andof fuel economy), it may be necessary1 232UMK0358Y

Fig. 2Schematic of the VE distributor pump with mechanical/hydraulic full-load torque controlLDA Manifold-pressure compensator.Controls the delivery quantity as a function of the charge-air pressure.HBA Hydraulically controlled torque control.Controls the delivery quantity as a function of the engine speed (not for pressure-charged engineswith LDA).Add-onmodulesand shutoffdevicesLFB Load-dependent start of delivery.Adaptation of pump delivery to load. For reduction of noise and exhaust-gas emissions.ADA Altitude-pressure compensator.Controls the delivery quantity as a function of atmospheric pressure.KSB Cold-start accelerator.Improves cold-start behavior by changing the start of delivery.GST Graded (or variable) start quantity.Prevents excessive start quantity during warm start.TLA Temperature-controlled idle-speed increase.Improves engine warm-up and smooth running when the engine is cold.ELAB Electrical shutoff device.A Cutoff port, n actual Actual engine speed (controlled variable), n setpoint Desired engine speed (referencevariable), Q F Delivery quantity, t M Engine temperature, t LU Ambient-air temperature, p L Charge-airpressure, p A Atmospheric pressure, p i Pump interior pressure.1 Full-load torque control with governor lever assembly, 2 Hydraulic full-load torque control.Basic pumpAdd-on modulet LU /t M n setpoint U on /U off p L/p ATLAGSTEngine-speedcontrolControl of injectedfuel quantityLDAADAELABHBA1 2An actualDriveFuelVane-type fuelsupplypumpHigh-pressurepump with distributorDelivery-valveassemblyInjectionnozzles Q FLFBp ipTiming deviceKSBt MUMK0359E33

Axial-pistondistributorpumps34to install torque control. In other words,the engine should receive precisely theamount of fuel it needs. The engine’sfuel requirement first of all climbs as afunction of engine speed and then levelsoff somewhat at higher speeds. Thefuel-delivery curve of an injection pumpwithout torque control is shown in Fig. 3.As can be seen, with the same setting ofthe control collar on the distributorplunger, the injection pump deliversslightly more fuel at high speeds than itdoes at lower speeds. This is due to thethrottling effect at the distributor plunger’scutoff port. This means that if theinjection pump’s delivery quantity isspecified so that maximum-possibletorque is developed at low enginespeeds, this would lead to the enginebeing unable to completely combust theexcess fuel injected at higher speedsand smoke would be the result togetherwith engine overheat. On the otherhand, if the maximum delivery quantityis specified so that it corresponds tothe engine’s requirements at maximumspeed and full-load, the engine will not beable to develop full power at low enginespeeds due to the delivery quantitydropping along with reductions in enginespeed. Performance would be belowoptimum. The injected fuel quantity musttherefore be adjusted to the engine’sFig. 3Fuel-delivery characteristics, with andwithout torque controla Negative, b Positive torque control.1 Excess injected fuel,2 Engine fuel requirement,3 Full-load delivery with torque control,Shaded area:Full-load delivery without torque control.mm 3strokeDelivery quantity Q Fa1 2 3Engine speed nbmin –1UMK0360Eactual fuel requirements. This is knownas “torque control”, and in the case ofthe distributor injection pump can beimplemented using the delivery valve, thecutoff port, or an extended governorleverassembly, or the hydraulicallycontrolled torque control (HBA). Full-loadtorque control using the governor leverassembly is applied in those cases inwhich the positive full-load torque controlwith the delivery valve no longer suffices,or a negative full-load torque control hasbecome necessary.Positive torque controlPositive torque control is required onthose injection pumps which deliver toomuch fuel at higher engine revs. Thedelivery quantity must be reduced asengine speed increases.Positive torque control usingthe delivery valveWithin certain limits, positive torquecontrol can be achieved by means of thedelivery valve, for instance by fitting asofter delivery-valve spring.Positive torque control usingthe cutoff portOptimization of the cutoff port’s dimensionsand shape permit its throttling effectto be utilized for reducing the deliveryquantity at higher engine speeds.Positive torque control using thegovernor lever assembly (Fig. 4a)The decisive engine speed for start oftorque control is set by preloading thetorque-control springs. When this speedis reached, the sliding-sleeve force (F M )and the spring preload must be inequilibrium, whereby the torque-controllever (6) abuts against the stop lug (5)of the tensioning lever (4). The free endof the torque-control lever (6) abutsagainst the torque-control pin (7).If engine speed now increases, thesliding-sleeve force acting against thestarting lever (1) increases and thecommon pivot point (M 4 ) of startinglever and torque-control lever (6)changes its position. At the same time,

the torque-control lever tilts around thestop pin (5) and forces the torquecontrolpin (7) in the direction of thestop, while the starting lever (1) swivelsaround the pivot point (M 2 ) and forces thecontrol collar (8) in the direction of reducedfuel delivery. Torque control ceasesas soon as the torque-control-pin collar(10) abuts against the starting lever (1).Negative torque controlNegative torque control may benecessary in the case of engines whichhave black-smoke problems in thelower speed range, or which mustgenerate specific torque characteristics.Similarly, turbocharged engines alsoneed negative torque control when themanifold-pressure compensator (LDA)has ceased to be effective. In this case,the fuel delivery is increased along withengine speed (Fig. 3).Negative torque control using thegovernor lever assembly (Fig. 4b)Once the starting spring (9) has beencompressed, the torque-control lever(6) applies pressure to the tensioninglever (4) through the stop lug (5). Thetorque-control pin (7) also abuts againstthe tensioning lever (4). If the slidingsleeveforce (F M ) increases due to risingengine speed, the torque-control leverFig. 4Torque control using the governor-lever assemblya Positive torque control,b Negative torque control.1 Starting lever,2 Torque-control spring, a3 Governor spring,4 Tensioning lever,3 45 Stop lug,6 Torque-control lever,7 Torque-control pin,8 Control collar,9 Starting spring,10 Pin collar,11 Stop point,M 2 Pivot point for 1 and 4,M 4 Pivot point for 1 and 6,2F M Sliding-sleeve force,1∆ s Control-collar travel.presses against the preloaded torquecontrolspring. As soon as the sliding-sleeveforce exceeds the torquecontrolspring force, the torque-controllever (6) is forced in the direction of thetorque-control-pin collar. As a result, thecommon pivot point (M 4 ) of the startinglever and torque-control lever changes itsposition. At the same time the startinglever swivels around its pivot point(M 2 ) and pushes the control collar (8)in the direction of increased delivery.Torque control ceases as soon as thetorque-control lever abuts against the pincollar.Negative torque control using hydraulicallycontrolled torque control HBAIn the case of naturally aspirated dieselengines, in order to give a special shapeto the full-load delivery characteristicas a function of engine speed, a formof torque control can be applied whichis similar to the LDA (manifold-pressurecompensator).Here, the shift force developed by thehydraulic piston is generated by thepressure in the pump interior, which inturn depends upon pump speed. Incontrast to spring-type torque control,within limits the shape of the full-loadcharacteristic can be determined by acam on a sliding pin.M 4567M 28b726F M4M 45910111M 28Add-onmodulesand shutoffdevicesF M∆ s∆ sUMK0362Y35

Axial-pistondistributorpumpsManifold-pressurecompensationExhaust-gas turbochargingBecause it increases the mass of airinducted by the engine, exhaust turbochargingboosts a diesel engine’s poweroutput considerably over that of a naturallyaspirated diesel engine, with littleincrease in dimensions and enginespeeds. This means that the brakehorsepower can be increased correspondingto the increase in air mass(Figure 6). In addition, it is often possibleto also reduce the specific fuel consumption.An exhaust-gas turbochargeris used to pressure-charge the dieselengine (Fig. 5).With an exhaust turbocharger, theengine’s exhaust gas, instead of simplybeing discharged into the atmosphere,is used to drive the turbocharger’sturbine at speeds which can exceed100,000 min –1 . Turbine and turbochargercompressor are connected through ashaft. The compressor draws in air,compresses it, and supplies it to theengine’s combustion chambers underpressure, whereby not only the airpressure rises but also the airtemperature. If temperatures becomeexcessive, some form of air cooling(intercooling) is needed between theturbocharger and the engine intake.Fig. 5: Diesel engine with exhaust-gas turbocharger36UMK0365Y

Power and torque comparison, naturally aspiratedand pressure-charged engineskWPower P eNaturally aspirated enginePressure-charged engineP eM dEngine speed nTorque M dmin –1 NmUMK0367EManifold-pressure compensator(LDA)The manifold-pressure compensator(LDA) reacts to the charge-air pressuregenerated by the exhaust-gas turbocharger,or the (mechanical) supercharger,and adapts the full-load deliveryto the charge-air pressure (Figs. 6and 7).AssignmentThe manifold-pressure compensator(LDA) is used on pressure-chargeddiesel engines. On these engines theinjected fuel quantity is adapted tothe engine’s increased air charge (due topressure-charging). If the pressurechargeddiesel engine operates with areduced cylinder air charge, the in-Fig. 6Fig. 7Distributor injection pump with manifold-pressure compensator (LDA)1 Governor spring, 2 Governor cover, 3 Reverse lever, 4 Guide pin, 5 Adjusting nut, 6 Diaphragm,7 Compression spring, 8 Sliding pin, 9 Control cone, 10 Full-load adjusting screw, 11 Adjusting lever,12 Tensioning lever, 13 Starting lever, 14 Connection for the charge-air, 15 Vent bore.M 1 pivot for 3.Add-onmodulesand shutoffdevices54M 11467158932110111213UMK0364Y37

Axial-pistondistributorpumps38jected fuel quantity must be adaptedto the lower air mass. This is performedby the manifold-pressure compensatorwhich, below a given (selectable)charge-air pressure, reduces the full-loadquantity.Design and constructionThe LDA is mounted on the top of thedistributor pump (Fig. 7). In turn, the topof the LDA incorporates the connectionfor the charge-air and the vent bore. Theinterior of the LDA is divided into twoseparate airtight chambers by a diaphragmto which pressure is applied bya spring. At its opposite end, the springis held by an adjusting nut with whichthe spring’s preload is set. This servesto match the LDA’s response point tothe charge pressure of the exhaustturbocharger. The diaphragm is connectedto the LDA’s sliding pin whichhas a taper in the form of a control cone.This is contacted by a guide pin whichtransfers the sliding-pin movements tothe reverse lever which in turn changesthe setting of the full-load stop. The initialsetting of the diaphragm and the slidingpin is set by the adjusting screw in the topof the LDA.Method of operationIn the lower engine-speed range thecharge-air pressure generated by theexhaust turbocharger and applied to thediaphragm is insufficient to overcome thepressure of the spring. The diaphragmremains in its initial position. As soon asthe charge-air pressure applied to thediaphragm becomes effective, the diaphragm,and with it the sliding pin andcontrol cone, shift against the force of thespring. The guide pin changes itsposition as a result of the control cone’svertical movement and causes thereverse lever to swivel around its pivotpoint M 1 (Fig. 7). Due to the force exertedby the governor spring, there is a nonpositiveconnection between tensioninglever, reverse lever, guide pin, andsliding-pin control cone. As a result, thetensioning lever follows the reverselever’s swivelling movement, causing thestarting lever and tensioning lever toswivel around their common pivot pointthus shifting the control collar in thedirection of increased fuel delivery. Fueldelivery is adapted in response to theincreased air mass in the combustionchamber (Fig. 8). On the other hand,when the charge-air pressure drops,the spring underneath the diaphragmpushes the diaphragm upwards, and withit the sliding pin. The compensationaction of the governor lever mechanismnow takes place in the reverse directionand the injected fuel quantity is adaptedto the change in charge pressure. Shouldthe turbocharger fail, the LDA reverts toits initial position and the engine operatesnormally without developing smoke. Thefull-load delivery with charge-air pressureis adjusted by the full-load stop screwfitted in the governor cover.Fig. 8Charge-air pressure: Operative rangea Turbocharger operation,b Normally aspirated operation.p 1 Lower charge-air pressure,p 2 Upper charge-air pressure.mm 3 /strokeInjected fuelquantity Qep 1LDA operativerangeabCharge-air pressure pp 2 mbarUMK0368E

Load-dependentcompensationDepending upon the diesel engine’s load,the injection timing (start of delivery)must be adjusted either in the “advance”or “retard” direction.Load-dependent start of delivery(LFB)AssignmentLoad-dependent start of delivery is designedso that with decreasing load(e.g., change from full-load to partload),with the control-lever position unchanged,the start of delivery is shiftedin the “retard” direction. And when engineload increases, the start of delivery(or start of injection) is shifted in the“advance” direction. These adjustmentslead to “softer” engine operation, andcleaner exhaust gas at part- and fullload.Fig. 9Design and constructionFor load-dependent injection timing,modifications must be made to the governorshaft, sliding sleeve, and pumphousing. The sliding sleeve is providedwith an additional cutoff port, andthe governor shaft with a ring-shapedgroove, a longitudinal passage and twotransverse passages (Fig. 9). The pumphousing is provided with a bore so thata connection is established from theinterior of the pump to the suction side ofthe vane-type supply pump.Method of operationAs a result of the rise in the supplypumppressure when the engine speedincreases, the timing device adjusts thestart of delivery in the “advance” direction.On the other hand, with the drop inthe pump’s interior pressure caused bythe LFB it is possible to implement a(relative) shift in the “retard” direction.This is controlled by the ring-shapedgroove in the governor shaft and thesliding-sleeve’s control port. The controlDesign and construction of the governor assembly with load-dependent start of delivery (LFB)1 Governor spring, 2 Sliding sleeve, 3 Tensioning lever, 4 Start lever, 5 Control collar,6 Distributor plunger, 7 Governor shaft, 8 Flyweights.M 2 Pivot point for 3 and 4.Add-onmodulesand shutoffdevices1 23478M 256UMK0369Y39

Axial-pistondistributorpumps40lever is used to input a given full-loadspeed. If this speed is reached and theload is less than full load, the speedincreases even further, because with arise in speed the flyweights swiveloutwards and shift the sliding sleeve. Onthe one hand, this reduces the deliveryquantity in line with the conventionalgoverning process. On the other, thesliding sleeve’s control port is opened bythe control edge of the governor-shaftgroove. The result is that a portion of thefuel now flows to the suction side throughthe governor shaft’s longitudinal andtransverse passages and causes apressure drop in the pump’s interior.This pressure drop results in the timingdevicepiston moving to a new position.This leads to the roller ring being turnedin the direction of pump rotation so thatstart of delivery is shifted in the “retard”direction. If the position of the controllever remains unchanged and the loadincreases again, the engine speed drops.The flyweights move inwards and thesliding sleeve is shifted so that its controlFig. 10Sliding-sleeve positions in the loaddependentinjection timing (LFB)a Start position (initial position),b Full-load position shortly before the controlport is opened,c Control port opened, pressure reduction inpump interior.1 Longitudinal bore in the governor shaft,2 Governor shaft, 3 Sliding-sleeve control port,4 Sliding-sleeve, 5 Governor-shaft transversepassage, 6 Control edge of the groove in thegovernor shaft, 7 Governor-shaft transversepassage.1 23 4abc5 6 7UMK0370Yport is closed again. The fuel in the pumpinterior can now no longer flow throughthe governor shaft to the suction side,and the pump interior pressure increasesagain. The timing-device piston shiftsagainst the force of the timingdevicespring and adjusts the roller ringso that start of delivery is shifted in the“advance” direction (Fig. 10).Atmospheric-pressurecompensationAt high altitudes, the lower air densityreduces the mass of the inducted air,and the injected full-load fuel quantitycannot burn completely. Smoke resultsand engine temperature rises. To preventthis, an altitude-pressure compensatoris used to adjust the full-loadquantity as a function of atmosphericpressure.Altitude-pressure compensator(ADA)Design and constructionThe construction of the ADA is identicalto that of the LDA. The only differencebeing that the ADA is equipped with ananeroid capsule which is connected toa vacuum system somewhere in thevehicle (e.g., the power-assisted brakesystem). The aneroid provides a constantreference pressure of 700 mbar(absolute).Method of operationAtmospheric pressure is applied to theupper side of the ADA diaphragm. Thereference pressure (held constant bythe aneroid capsule) is applied to thediaphragm’s underside. If the atmosphericpressure drops (for instancewhen the vehicle is driven in themountains), the sliding bolt shifts verticallyaway from the lower stop and,similar to the LDA, the reverse levercauses the injected fuel quantity to bereduced.

Cold-start compensationThe diesel engine’s cold-start characteristicsare improved by fitting a coldstartcompensation module which shiftsthe start of injection in the “advance”direction. Operation is triggered eitherby the driver using a bowden cable inthe cab, or automatically by means ofa temperature-sensitive advance mechanism(Fig. 11).Mechanical cold-start accelerator(KSB) on the roller ringMechanical cold-start accelerator (KSB)engaging in roller ring (cold-start position)1 Lever, 2 Access window, 3 Ball pin,4 Longitudinal slot, 5 Pump housing, 6 Roller ring,7 Roller in the roller ring, 8 Timing-device piston,9 Torque-control pin, 10 Sliding block. 11 Timingdevicespring, 12 Shaft, 13 Coil spring.1 2 3 456Add-onmodulesand shutoffdevicesDesign and constructionThe KSB is attached to the pumphousing, the stop lever being connectedthrough a shaft to the inner leveron which a ball pin is eccentricallymounted. The ball pin’s head extendsinto the roller ring (a version is availablein which the advance mechanism engagesin the timing-device piston). Thestop lever’s initial position is definedby the stop itself and by the helicalcoiled spring. Attached to the top ofthe stop lever is a bowden cable whichserves as the connection to the manualor to the automatic advance mechanism.The automatic advance mechanism ismounted on the distributor pump, whereasthe manual operating mechanism isin the driver’s cab (Fig. 12).Fig. 1113 1210 9Method of operationAutomatically and manually operatedcold-start accelerators (KSB) differ onlywith regard to their external advancemechanisms. The method of operation isidentical. With the bowden cable notpulled, the coil spring pushes the stoplever up against the stop. Ball pin androller ring are in their initial position. Theforce applied by the bowden cableMechanical cold-start accelerator (KSB), advance mechanism with automatic operation(cold-start position)1 Clamp,2 Bowden cable,3 Stop lever,4 Coil spring,5 KSB advance lever,6 Control devicesensitive to thetemperature ofthe coolant andthe surroundings.1 21178UMK0373YFig. 123 4 5 6UMK0372Y41

Axial-pistondistributorpumpscauses the stop lever, the shaft, the innerlever and the ball pin, to swivel andchange the roller ring’s setting so that thestart of delivery is advanced. The ball pinengages in a slot in the roller ring, whichmeans that the timing-device pistoncannot rotate the roller ring any further inthe “advance” direction until a givenengine speed has been exceeded.In those cases in which the KSB istriggered by the driver from the cab(timing-device KSB), independent of theadvance defined by the timing device (a),an advance of approx. 2.5° camshaft ismaintained (b), as shown in Fig. 13. Withthe automatically operated KSB, thisadvance depends upon the enginetemperature or ambient temperature.The automatic advance mechanism usesa control device in which a temperaturesensitiveexpansion element converts theengine temperature into a stroke movement.The advantage of this method isthat for a given temperature, the optimumstart of delivery (or start of injection) isalways selected.There are a number of different leverconfigurations and operating mechanismsin use depending upon thedirection of rotation, and on which sidethe KSB is mounted.Temperature-controlled idle-speedincrease (TLA)The TLA is also operated by the controldevice and is combined with the KSB.Here, when the engine is cold, the ballpin at the end of the elongated KSBadvance lever presses against the engine-speedcontrol lever and lifts it awayfrom the idle-speed stop screw. The idlespeed increases as a result, and roughrunning is avoided. When the engine haswarmed up, the KSB advance lever abutsagainst its stop and, as a result, theengine-speed control lever is also upagainst its stop and the TLA is no longereffective (Fig. 14).Hydraulic cold-start acceleratorAdvancing the start of injection byshifting the timing-device piston hasonly limited applications. In the case ofthe hydraulic start-of-injection advance,the speed-dependent pump interiorpressure is applied to the timing-devicepiston. In order to implement a startof-injectionadvance, referred to theconventional timing-device curve, thepump interior pressure is increasedautomatically. To do so, the automaticcontrol of pump interior pressure ismodified through a bypass in thepressure-holding valve.Fig. 13Effect of the mechanical cold-startaccelerator (KSB)a Timing-device advance,b Minimum advance (approx. 2.5° camshaft).°cmsFig. 14Mechanical cold-start accelerator(automatically controlled) with temperaturedependentidle-speed increase1 Engine-speed control lever, 2 Ball pin,3 KSB advance lever, 4 Stop.42Injection-timing advance2.5°b00Pump speed pa1234min –1UMK0374EUMK0377Y

Design and constructionThe hydraulic cold-start acceleratorcomprises a modified pressure-controlvalve, a KSB ball valve, a KSB controlvalve, and an electrically heated expansionelement.Method of operationThe fuel delivered by the fuel-supplypump is applied to one of the timingdevice piston’s end faces via the injectionpump’s interior. In accordance with theinjection pump’s interior pressure, thepiston is shifted against the forceof its spring and changes the startof-injectiontiming. Pump interiorpressure is determined by a pressurecontrolvalve which increases pumpinterior pressure along with increasingpump speed and the resulting rise inpump delivery (Fig. 15).There is a restriction passage in thepressure-control valve’s plunger in orderto achieve the pressure increaseneeded for the KSB function, and theresulting advance curve shown as adotted line in Fig. 16. This ensures thatthe same pressure is effective at thespring side of the pressure-controlvalve. The KSB ball-type valve has acorrespondingly higher pressure leveland is used in conjunction with thethermo-element both for switching-onand switching-off the KSB function, aswell as for safety switchoff. Using anFig. 15Hydraulic cold-start accelerator (KSB)11 Pressure-control valve,12 Valve plunger,13 Restriction passage,14 Internal pressure,15 Fuel-supply pump,16 Electrically heatedexpansion element,17 KSB ball valve,18 Pressureless fuel return,19 KSB control valve,adjustable,10 Timing device.Effect of the hydraulic cold-startaccelerator (KSB)1 Injection-timing advance.adjusting screw in the integrated KSBcontrol valve, the KSB function can beset to a given engine speed. The fuelsupply pump pressure shifts the KSBcontrol valve’s plunger against theforce of a spring. A damping restriction isused to reduce the pressure fluctuationsat the control plunger. The KSBpressure characteristic is controlled byits plunger’s control edge and the sectionat the valve holder. The KSB functionis adapted by correct selection of theKSB control valve’s spring rate and itscontrol section. When the warm engineis started, the expansion element hasalready opened the ball valve due to theprevailing temperature.1234°cmsInjection-timing advance51Pump speed p786min –1UMK0379EFig. 16Add-onmodulesand shutoffdevices109UMK1195Y43

Axial-pistondistributorpumps44Engine shutoffAssignmentThe principle of auto-ignition as appliedto the diesel engine means that theengine can only be switched off byinterrupting its supply of fuel.Normally, the mechanically governeddistributor pump is switched off by asolenoid-operated shutoff (ELAB). Onlyin special cases is it equipped with amechanical shutoff device.Electrical shutoff device(ELAB)The electrical shutoff (Fig. 17) using thevehicle’s key-operated starting switch iscoming more and more to the forefrontdue to its convenience for the driver.On the distributor pump, the solenoidvalve for interrupting the fuel supply isinstalled in the top of the distributorhead. When the engine is running, thesolenoid is energized and the valvekeeps the passage into the injectionpump’s high-pressure chamber open(armature with sealing cone has pulledin). When the driving switch is turnedto “OFF”, the current to the solenoidwinding is also cut, the magnetic fieldcollapses, and the spring forces thearmature and sealing cone back ontothe valve seat again. This closes theinlet passage to the high-pressurechamber, the distributor-pump plungerceases to deliver fuel, and the enginestops. From the circuitry point of view,there are a variety of different possibilitiesfor implementing the electricalshutoff (pull or push solenoid).Mechanical shutoff deviceOn the injection pump, the mechanicalshutoff device is in the form of a leverassembly (Fig. 18). This is located inthe governor cover and comprises anouter and an inner stop lever. The outerlever is operated by the driver from insidethe vehicle (for instance by means ofbowden cable). When the cable ispulled, both levers swivel around theircommon pivot point, whereby the innerstop lever pushes against the start leverof the governor-lever mechanism. Thisswivels around its pivot point M 2 andshifts the control collar to the shutoffposition. The distributor plunger’s cutoffport remains open and the plungerdelivers no fuel.Fig. 17Electrical shutoff device(pull solenoid)1 Inlet passage, 2 Distributor plunger,3 Distributor head, 4 Push or pull solenoid,5 High-pressure chamber.123Fig. 18Mechanical shutoff device1 Outer stop lever, 2 Start lever,3 Control collar, 4 Distributor plunger,5 Inner stop lever, 6 Tensioning lever,7 Cutoff port.M 2 Pivot point for 2 and 6.12344556M 27UMK0382YUMK0380Y

Testing and calibrationInjection-pump testbenchesPrecisely tested and calibrated injectionpumps and governors are the prerequisitefor achieving the optimum fuel-consumption/performanceratio and compliancewith the increasingly stringentexhaust-gas legislation. And it is at thispoint that the injection-pump test benchbecomes imperative. The most importantframework conditions for the test benchand for the testing itself are defined inISO-Standards which, in particular, placevery high demands upon the rigidity anduniformity of the pump drive.The injection pump under test isclamped to the test-bench bed and connectedat its drive end to the test-benchcoupling. Drive is through an electricmotor (via hydrostatic or manuallyswitchedtransmission to flywheel andFig. 18Continuous injected-fuel-quantitymeasuring system1 Calibrating-oil tank, 2 Injection pump,3 Calibrating nozzle, 4 Measuring cell,5 Pulse counter, 6 Display monitor.26coupling, or with direct frequency control).The pump is connected to the bench’scalibrating-oil supply via oil inlet andoutlet, and to its delivery measuringdevice via high-pressure lines. Themeasuring device comprises calibratingnozzles with precisely set openingpressures which inject into the bench’smeasuring system via spray dampers. Oiltemperature and pressure is adjusted inaccordance with test specifications.There are two methods for fuel-deliverymeasurement. One is the so-calledcontinuous method. Here, a precisiongear pump delivers per cylinder and unit oftime, the same quantity of calibrating-oilas the quantity of injected fuel. The gearpump’s delivery is therefore a measure ofdelivery quantity per unit of time. A computerthen evaluates the measurementresults and displays them as a bar charton the screen. This measuring methodis very accurate, and features goodreproducibility (Fig. 1).The other method for fuel-delivery measurementuses glass measuring graduates.The fuel to be measured is at firstdirected past the graduates and back tothe tank with a slide. When the specifiednumber of strokes has been set on thestroke-counting mechanism the measurementstarts, and the slide opens andthe graduates fill with oil. When the setnumber of strokes has been completed,the slider cuts off the flow of oilagain. The injected quantity can be readoff directly from the graduates.Testing andcalibration34Engine tester for dieselengines 15MUWT0059YThe diesel-engine tester is necessaryfor the precise timing of the injectionpump to the engine. Without opening thehigh-pressure lines, this tester measuresthe start of pump delivery, injectiontiming, and engine speeds. A sensoris clamped over the high-pressure lineto cylinder 1, and with the stroboscopictiming light or the TDC sensor for detectingcrankshaft position, the testercalculates start of delivery and injectiontiming.45

Axial-pistondistributorpumps46Nozzles andnozzle holdersThe injection nozzles and their respectivenozzle holders are vitally importantcomponents situated between the in-lineinjection pump and the diesel engine.Their assignments are as follows:– Metering the injection of fuel,– Management of the fuel,– Defining the rate-of-discharge curve,– Sealing-off against the combustionchamber.Considering the wide variety of combustionprocesses and the different formsof combustion chamber, it is necessarythat the shape, “penetration force”, andatomization of the fuel spray injected bythe nozzle are adapted to the prevailingconditions. This also applies to the injectiontime, and the injected fuel quantityper degree camshaft.Since the design of the nozzle-holdercombination makes maximum use ofstandardized components and assemblies,this means that the required flexibilitycan be achieved with a minimum ofcomponents. The following nozzles andnozzle holders are used with in-line injectionpumps:– Pintle nozzles (DN..) for indirect-injection(IDI) engines, and– Hole-type nozzles (DLL../DLSA..) fordirect-injection (DI) engines,– Standard nozzle holders (singlespringnozzle holders), with and withoutneedle-motion sensor, and– Two-spring nozzle holders, with andwithout needle-motion sensor.Pintle nozzlesApplicationPintle nozzles are used with in-line injectionpumps on indirect-injection engines(pre-chamber and whirl-chamberengines).In this type of diesel engine, the air/fuelmixture is for the most part formed by theair’s vortex work. The injected fuel sprayserves to support this mixture-formationprocess.The following types of pintle nozzle areavailable:– Standard pintle nozzles (Fig. 1),– Throttling pintle nozzles, and– Flat-cut pintle nozzles (Fig. 2).Design and constructionAll pintle nozzles are of practically identicaldesign, the only difference being inthe pintle’s geometry:Standard pintle nozzleOn the standard pintle nozzle, the nozzleneedle is provided with a pintle whichextends into the injection orifice of thenozzle body in which it is free to movewith a minimum of play. The injectionspray can be matched to the engine’srequirements by appropriate choice ofdimensions and pintle designs.Fig. 1Standard pintle nozzle1 Lift stop surface, 2 Ring groove, 3 Needle guide,4 Nozzle-body shaft, 5 Pressure chamber,6 Pressure shoulder, 7 Seat lead-in, 8 Inlet port,9 Nozzle-body shoulder, 10 Nozzle-body collar,11 Sealing surface, 12 Pressure shaft,13 Pressure-pin contact surface.13123456121110987UMK1390Y

Throttling pintle nozzleThe throttling pintle nozzle is a pintlenozzle with special pintle dimensions.The special pintle design serves to definethe shape of the rate-of-discharge curve.When the nozzle needle lifts it first of allopens a small annular gap so that only asmall amount of fuel is injected (throttlingeffect).As needle lift increases (due to pressurerise), the spray orifice is opened increasinglyuntil the major portion of the injection(main injection) takes place towardsthe end of needle lift. Since the pressurein the combustion chamber rises lesssharply, this shaping of the rate-of-injectioncurve leads to “softer” combustion.This results in quieter combustion in thepart-load range. In other words, it ispossible to shape the required rate-ofdischargecurve by means of the pintleshape, the characteristic of the nozzleneedle’s spring, and the throttling gap.Fig. 2Flat-cut pintle nozzlea Side view, b Front view.1 Needle seat, 2 Nozzle-body floor,3 Throttling pintle, 4 Flat cut, 5 Injection orifice,6 Profiled pintle, 7 Total overlap,8 Cylindrical overlap, 9 Nozzle-body seat.aFlat-cut pintle nozzleThis nozzle’s pintle has a ground surfacewhich opens a flow cross-section in additionto the annular gap when the pintleopens (only slight needle lift). The resultingincreased flow volume prevents depositsforming in this flow channel. This isthe reason why flat-cut pintle nozzlescoke-up far less, and any coking whichdoes take place is more uniform. Theannular gap between spray orifice andthrottling pintle is very small (less than10 µm). Very often, the flat-cut pintle surfaceis parallel to the nozzle-needle axis.Referring to Fig. 3, with an additionalinclined cut on the pintle, the gradient ofthe injected-fuel-quantity curve’s flat portioncan be increased so that the transitionto full nozzle opening is lessabrupt. Specially shaped pintles, such asthe “radius” or “profile surface” types, canbe applied to match the flow curve toengine-specific requirements. Part-loadnoise and vehicle driveability are bothimproved as a result.Fig. 3Flow quantity as a function of needle lift andnozzle version1 Throttling pintle nozzle,2 Throttling pintle nozzle with inclined cut onpintle (flat-cut pintle nozzle)l/hNozzlesand nozzleholders19830027345b6Flow quantity2001002 1UMK1391Y00 0.20.4 0.6 0.8 mmNeedle liftUMK1397E47

Axial-pistondistributorpumpsHole-type nozzlesApplicationHole-type nozzles are used with in-lineinjection pumps on direct-injection engines.One differentiates between:– Sac-hole, and– Seat-hole nozzles.The hole-type nozzles also vary accordingto their size:– Type P with 4 mm needle diameter,and– Type S with 5 and 6 mm needle diameters.Design and constructionThe spray holes are located on the envelopeof a spray cone (Fig. 4). The numberof spray holes and their diameter dependupon:– The injected fuel quantity,– The combustion-chamber shape, and– The air swirl in the combustion chamber.The input edges of the spray holes canbe rounded by hydro-erosive (HE) machining.Fig. 4Spray coneγ Spray-cone offset angle, d Spray cone.γAt those points where high flow ratesoccur (spray-hole entrance), the abrasiveparticles in the hydro-erosive (HE) mediumcause material loss.This so-called HE-rounding process canbe applied to both sac-hole and seat-holenozzles, whereby the target is:– Prevent in advance the edge wearcaused by abrasive particles in the fueland/or– Reduce the flow tolerance.For low hydrocarbon emissions, it ishighly important that the volume filledwith fuel (residual volume) below theedge of the nozzle-needle seat is kept toa minimum. Seat-hole nozzles are thereforeused.DesignsSac-hole nozzleThe spray holes of the sac-hole nozzle(Fig. 5) are arranged in the sac hole.In the case of a round nozzle tip (Fig. 6a),depending upon design the spray holesare drilled mechanically or by means ofelectrochemical machining (e.c.m.).Sac-hole nozzles with conical tip (Figs.6b and 6c) are always drilled using e.c.m.Sac-hole nozzles are available– With cylindrical, and– Conical sac holesin a variety of different dimensions.Sac-hole nozzle with cylindrical sac holeand round tip (Fig. 6a):This nozzle’s sac hole has a cylindricaland a semispherical portion, and permitsa high level of design freedom withrespect to– Number of spray holes,– Spray-hole length, and– Injection angle.48δUMK1402YThe nozzle tip is semispherical, andtogether with the shape of the sac hole,ensures that the spray holes are ofidentical length.

Sac-hole nozzle with cylindrical sac holeand conical tip (6b):This type of nozzle is used exclusivelywith spray-hole lengths of 0.6 mm. Thetip’s conical shape enables the wallthickness to be increased between thethroat radius and the nozzle-body seatwith an attending improvement of nozzletipstrength.Sac-hole nozzle with conical sac holeand conical tip (Fig. 6c):Due to the conical shape of this nozzle’ssac hole, its volume is less than that of anozzle with cylindrical sac hole. Thevolume is between that for a seat-holenozzle and a sac-hole nozzle with cylindricalsac hole. In order to achieve uniformtip-wall thickness, the tip’s conicaldesign corresponds to that of the sachole.Nozzlesand nozzleholdersFig. 5Sac-hole nozzle1 Pressure shaft, 2 Needle-lift stop face,3 Inlet passage, 4 Pressure shoulder,5 Needle shaft, 6 Nozzle tip,7 Nozzle-body shaft, 8 Nozzle-body shoulder,9 Pressure chamber, 10 Needle guide,11 Nozzle-body collar, 12 Locating hole,13 Sealing surface,14 Pressure-pin contact surface.Fig. 6Sac-hole shapesa Cylindrical sac hole with round tip,b Cylindrical sac hole with conical tip,c Conical sac hole with conical tip.1 Shoulder, 2 Seat entrance, 3 Needle seat,4 Needle tip, 5 Injection orifice,6 Injection-orifice entrance, 7 Sac hole,8 Throat radius, 9 Nozzle-tip cone,10 Nozzle-body seat, 11 Damping cone.a1234511109876bcUMK1403YUMK1650Y49

Axial-pistondistributorpumpsSeat-hole nozzleIn order to minimise the residual volume– and therefore the HC emissions – thestart of the spray hole is located in theseat taper, and with the nozzle closed it iscovered almost completely by the nozzleneedle. This means that there is no directconnection between the sac hole and thecombustion chamber (Figs. 7 and 8). Thesac-hole volume here is much lower thanthat of the sac-hole nozzle. Compared tosac-hole nozzles, seat-hole nozzles havea much lower loading limit and are thereforeonly manufactured as Size P with aspray-hole length of 1 mm.For reasons of strength, the nozzle tip isconically shaped. The spray holes arealways formed using e.c.m. methods.Fig. 7Seat-hole nozzleStandard nozzle holdersAssignments and designsNozzle holders with hole-type nozzles incombination with a radial-piston distributorinjection pump are used on DIengines.With regard to the nozzle holders, onedifferentiates between– Standard nozzle holders (singlespringnozzle holders) with and withoutneedle-motion sensor, and– Two-spring nozzle holders, with andwithout needle-motion sensor.ApplicationThe nozzle holders described here havethe following characteristics:– Cylindrical external shape with diametersbetween 17 and 21 mm,– Bottom-mounted springs (leads to lowmoving masses),– Pin-located nozzles for direct-injectionengines, and– Standardised components (springs,pressure pin, nozzle-retaining nut)make combinations an easy matter.50Fig. 8Seat-hole nozzle: Tip shapeUMK1408Y UMK1407YDesignThe nozzle-and-holder assembly is composedof the injection nozzle and thenozzle holder.The nozzle holder comprises the followingcomponents (Fig. 9):– Nozzle-holder body,– Intermediate element,– Nozzle-retaining nut,– Pressure pin,– Spring,– Shim, and– Locating pins.The nozzle is centered in the nozzle bodyand fastened using the nozzle-retainingnut. When nozzle body and retaining nutare screwed together, the intermediateelement is forced up against the sealingsurfaces of nozzle body and retainingnut. The intermediate element serves asthe needle-lift stop and with its locatingpins centers the nozzle in the nozzleholderbody.

The nozzle-holder body contains the– Pressure pin,– Spring, and– Shim.The spring is centered in position by thepressure pin, whereby the pressure pin isguided by the nozzle-needle’s pressureshaft.The nozzle is connected to the injectionpump’s high-pressure line via the nozzleholderfeed passage, the intermediateelement, and the nozzle-body feed passage.If required, an edge-type filter canbe installed in the nozzle holder.Fig. 9Standard nozzle holder1 Edge-type filter, 2 Inlet passage,3 Pressure pin, 4 Intermediate element,5 Nozzle-retaining nut, 6 Wall thickness,7 Nozzle, 8 Locating pins, 9 Spring,10 Shim, 11 Leak-fuel passage,12 Leak-fuel connection thread,13 Nozzle-holder body, 14 Connection thread,15 Sealing cone.1151413Nozzlesand nozzleholdersMethod of operationThe nozzle-holder spring applies pressureto the nozzle needle through thepressure pin. The spring’s initial tensiondefines the nozzle’s opening pressurewhich can be adjusted using a shim.On its way to the nozzle seat, the fuel passesthrough the nozzle-holder inlet passage,the intermediate element, and thenozzle nody. When injection takes place,the nozzle needle is lifted by the injectionpressure and fuel is injected through theinjection orifices into the combustionchamber. Injection terminates as soon asthe injection pressure drops far enough forthe nozzle spring to force the nozzleneedle back onto its seat.21211109Two-spring nozzle holdersApplicationThe two-spring nozzle holder is a furtherdevelopment of the standard nozzleholder, and serves to reduce combustionnoise particularly in the idle and part-loadranges.DesignThe two-spring nozzle holder featurestwo springs located one behind the other.At first, only one of these springs has aninfluence on the nozzle needle and assuch defines the initial opening pressure.The second spring is in contact with astop sleeve which limits the needle’sinitial stroke.345876UMK1413Y51

Axial-pistondistributorpumpsFig. 10Two-spring nozzle holder for direct-injection(DI) engines1 Nozzle-holder body, 2 Shim,3 Spring 1, 4 Pressure pin,5 Guide element, 6 Spring 2,7 Pressure pin, 8 Spring seat,9 Shim, 10 Intermediate element,11 Stop sleeve,12 Nozzle needle,13 Nozzle-retaining nut,14 Nozzle body.h 1 Initial stroke,h 2 Main stroke.123When strokes take place in excess of theinitial stroke, the stop sleeve lifts and bothsprings have an effect upon the nozzleneedle (Fig. 10).Method of operationDuring the actual injection process, thenozzle needle first of all opens an initialamount so that only a small volume offuel is injected into the combustionchamber.Along with increasing injection pressurein the nozzle holder though, the nozzleneedle opens completely and the mainquantity is injected (Fig. 11). This 2-stagerate-of-discharge curve leads to “softer”combustion and to a reduction in noise.Nozzle holders with needlemotionsensor4567891011121314ApplicationThe start-of-injection point is an importantparameter for optimum diesel-engineoperation. For instance, its evaluationpermits load and speed-dependent injectiontiming, and/or control of the exhaustgasrecirculation (EGR) rate.Fig. 11Comparison of needle-lift curvesa Standard nozzle holder (single-spring nozzleholder),b Two-spring nozzle holder.h 1 Initial stroke, h 2 Main stroke.amm0.40.20bmm0.4h 2h 1Nozzle-needle lift0.2h 252UMK1423-1Y00 1Timeh 12 msUMK1422E

This necessitates a nozzle holder withneedle-motion sensor (Fig. 13) whichoutputs a signal as soon as the nozzleneedle opens.DesignWhen it moves, the extended pressurepin enters the current coil.The degree to which it enters the coil(overlap length “X” in Fig. 14) determinesthe strength of the magnetic flux.Method of operationThe magnetic flux in the coil changes asa result of nozzle-needle movement andinduces a signal voltage which is proportionalto the needle’s speed of movementbut not to the distance it has travelled.This signal is processed directly in anevaluation circuit (Fig. 12).When a given threshold voltage is exceeded,this serves as the signal tothe evaluation circuit for the start ofinjection.Two-spring nozzle holder with needle-motionsensor for direct-injection (DI) engines1 Nozzle-holder body, 2 Needle-motion sensor,3 Spring 1, 4 Guide element, 5 Spring 2,6 Pressure pin, 7 Nozzle-retaining nut.123456Nozzlesand nozzleholders7Fig. 12Comparison between a needle-lift curve andthe corresponding signal-voltage curve of theneedle-motion sensorNeedle liftabThesholdvoltageNeedle-liftsensorsignalNeedlemotionsensorsignalFig. 14Needle-motion sensor in a two-spring nozzleholder for direct-injection (DI) engines1 Adjusting pin, 2 Terminal,3 Current coil, 4 Pressure pin,5 Spring seat.X Overlap length.12UMK1588D UMK1588YFig. 13Signal voltageStart-of-injectionsignal°cksUMK1427EX345UMK1529Y53

Axial-pistondistributorpumps,VE-EDCElectronically-controlledaxial-piston distributor fuelinjectionpumps VE-EDCMechanical diesel-engine speed control(mechanical governing) registers a widevariety of different operating statusesand permits high-quality A/F mixtureformation.The Electronic Diesel Control (EDC)takes additional requirements into account.By applying electronic measurement,highly-flexible electronic data processing,and closed control loops withelectric actuators, it is able to processmechanical influencing variables which itwas impossible to take into account withthe previous purely mechanical control(governing) system.The EDC permits data to be exchangedwith other electronic systems in theFig. 1Electronic Diesel Control (EDC): System blocksvehicle (for instance, traction controlsystem (TCS), and electronic transmission-shiftcontrol). In other words, it canbe integrated completely into the overallvehicle system.System blocksThe electronic control is divided intothree system blocks (Fig. 1):1. Sensors for registering operatingconditions. A wide variety of physicalquantities are converted into electricalsignals.2. Electronic control unit (ECU) withmicroprocessors which processes the in-SensorsECUActuatorsNeedle-motion sensorInjectedfuel quantityTemperature sensors(water, air, fuel)EngineshutoffFuel-injection pumpSensor forcontrol-collar positionStart ofinjectionAir-flow sensorMicroprocessorEGRTransducer withEGR valveEngine-speed sensorStartingcontrolGlow control unitVehicle-speed sensorAtmospheric-pressuresensorSetpoint generatorsDiagnosis54Accelerator-pedal sensorSpeed-selection leverMapsDiagnosis displayUMK0467E

formation in accordance with specificcontrol algorithms, and outputs correspondingelectrical signals.3. Actuators which convert the ECU’selectrical output signals into mechanicalquantities.ComponentsSensorsThe positions of the accelerator and thecontrol collar in the injection pump areregistered by the angle sensors. Theseuse contacting and non-contactingmethods respectively. Engine speed andTDC are registered by inductive sensors.Sensors with high measuring accuracyand long-term stability are used for pressureand temperature measurements.The start of injection is registered by asensor which is directly integrated in thenozzle holder and which detects the startof injection by sensing the needle movement(Figs. 2 and 3).Electronic control unit (ECU)The ECU employs digital technology. Themicroprocessors with their input andoutput interface circuits form the heartof the ECU. The circuitry is completedby the memory units and devices forthe conversion of the sensor signalsinto computer-compatible quantities. TheECU is installed in the passenger compartmentto protect it from external influences.There are a number of different mapsstored in the ECU, and these come intoeffect as a function of such parametersas: Load, engine speed, coolant temperature,air quantity etc. Exacting demandsare made upon interferenceimmunity. Inputs and outputs are shortcircuit-proofand protected against spuriouspulses from the vehicle electricalsystem. Protective circuitry and mechanicalshielding provide a high levelof EMC (Electro-Magnetic Compatibility)against outside interference.Electroniccontrol fordistributorpumpsFig. 2 Fig. 3Sensor signals1 Untreated signal from the needle-motion sensor(NBF),2 Signal derived from the NBF signal,3 Untreated signal from the engine-speed signal,4 Signal derived from untreated engine-speedsignal,5 Evaluated start-of-injection signal.Nozzle-and-holder assembly withneedle-motion sensor (NBF)1 Setting pin, 2 Sensor winding, 3 Pressure pin,4 Cable, 5 Plug.1421235345UMK0466YUMK0468Y55

Axial-pistondistributorpumps,VE-EDCSolenoid actuator for injectedfuelquantity controlThe solenoid actuator (rotary actuator)engages with the control collar througha shaft (Fig. 4). Similar to the mechanicallygoverned fuel-injection pump, thecutoff ports are opened or closed dependingupon the control collar’s position.The injected fuel quantity can beinfinitely varied between zero andmaximum (e.g., for cold starting). Usingan angle sensor (e.g., potentiometer),the rotary actuator’s angle of rotation,and thus the position of the control collar,are reported back to the ECU andused to determine the injected fuelquantity as a function of engine speed.When no voltage is applied to the actuator,its return springs reduce the injectedfuel quantity to zero.Fig. 4Solenoid valve forstart-of-injection controlThe pump interior pressure is dependentupon pump speed. Similar to themechanical timing device, this pressureis applied to the timing-device piston(Fig. 4). This pressure on the timingdevicepressure side is modulated by aclocked solenoid valve.With the solenoid valve permanentlyopened (pressure reduction), start ofinjection is retarded, and with it fullyclosed (pressure increase), start of injectionis advanced. In the intermediaterange, the on/off ratio (the ratio ofsolenoid valve open to solenoid valveclosed) can be infinitely varied by theECU.Distributor injection pump for electronic diesel control1 Control-collar position sensor, 2 Solenoid actuator for the injected fuel quantity, 3 Electromagneticshutoff valve, 4 Delivery plunger, 5 Solenoid valve for start-of-injection timing, 6 Control collar.12345665UMK0464Y

Closed control loops (Fig. 5)Injected fuel quantityThe injected fuel quantity has a decisiveinfluence upon the vehicle’s starting,idling, power output and driveabilitycharacteristics, as well as upon its particulateemissions. For this reason, thecorresponding maps for start quantity,idle, full load, accelerator-pedal characteristic,smoke limitation, and pumpcharacteristic, are programmed into theECU. The driver inputs his or her requirementsregarding torque or enginespeed through the accelerator sensor.Taking into account the stored mapdata, and the actual input values fromthe sensors, a setpoint is calculated forthe setting of the rotary actuator in thepump. This rotary actuator is equippedFig. 5with a check-back signalling unit andensures that the control collar is correctlyset.Start of injectionThe start of injection has a decisive influenceupon starting, noise, fuel consumption,and exhaust emissions. Startof-injectionmaps programmed into theECU take these interdependencies intoaccount. A closed control loop is usedto guarantee the high accuracy of thestart-of-injection point. A needle-motionsensor (NBF) registers the actual start ofinjection directly at the nozzle andcompares it with the programmed startof injection (Figs. 2 and 3). Deviationsresult in a change to the on/off ratio ofthe timing-device solenoid valve, whichcontinues until deviation reaches zero.Closed control loop of the electronic diesel control (EDC)Q Air-flow quantity, n act Engine speed (actual), p A Atmospheric pressure, s set Control-collar signal(setpoint), s act Control-collar position (actual), s v set Timing-device signal (setpoint), t K Fuel temperature,t L Intake-air temperature, t M Engine temperature, t i act Start of injection (actual).FuelAcceleratorpedalOperator’spanelAirElectroniccontrol fordistributorpumpsELABOn/OffECUCruisecontrolVEpumps setpointt Ks actualStartquantitycontrolEGRcontrolp As v setpointStart-ofinjectioncontrolInjectedfuel-quantitycontrolt LQ lVehiclespeedsensorInjectionnozzlet i actualtMn actualExhaustemissionsEGR valveEngine and vehicleUMK0465E57

Axial-pistondistributorpumps,VE-EDC58This clocked solenoid valve is used tomodulate the positioning pressure at thetiming-device piston, and this results inthe dynamic behavior being comparableto that obtained with the mechanicalstart-of-injection timing.Because during engine overrun (withinjection suppressed) and engine startingthere are either no start-of-injectionsignals available, or they are inadequate,the controller is switched off and anopen-loop-control mode is selected. Theon/off ratio for controlling the solenoidvalve is then taken from a control map inthe ECU.Exhaust-gas recirculation (EGR)EGR is applied to reduce the engine’stoxic emissions. A defined portion of theexhaust gas is tapped-off and mixedwith the fresh intake air. The engine’sintake-air quantity (which is proportionalto the EGR rate) is measured by an airflowsensor and compared in the ECUwith the programmed value for the EGRmap, whereby additional engine andinjection data for every operating pointare taken into account.In case of deviation, the ECU modifiesthe triggering signal applied to anelectropneumatic transducer. This thenadjusts the EGR valve to the correctEGR rate.Cruise controlAn evaluated vehicle-speed signal iscompared with the setpoint signal inputtedby the driver at the cruise-controlpanel. The injected fuel quantity is thenadjusted to maintain the speed selectedby the driver.Supplementary functionsThe electronic diesel control (EDC)provides for supplementary functionswhich considerably improve the vehicle’sdriveability compared to themechanically governed injection pump.Active anti-buck dampingWith the active anti-buck damping(ARD) facility, the vehicle’s unpleasantlongitudinal oscillations can be avoided.Idle-speed controlThe idle-speed control avoids engine“shake” at idle by metering the appropriateamount of fuel to each individualcylinder.Safety measuresSelf-monitoringThe safety concept comprises theECU’s monitoring of sensors, actuators,and microprocessors, as well as of thelimp-home and emergency functionsprovided in case a component fails. Ifmalfunctions occur on important components,the diagnostic system not onlywarns the driver by means of a lamp inthe instrument panel but also provides afacility for detailed trouble-shooting inthe workshop.Limp-home and emergencyfunctionsThere are a large number of sophisticatedlimp-home and emergency functionsintegrated in the system. For instanceif the engine-speed sensor fails,a substitute engine-speed signal isgenerated using the interval betweenthe start-of-injection signals from theneedle-motion sensor (NBF). And if theinjected-fuel quantity actuator fails, aseparate electrical shutoff device(ELAB) switches off the engine. Thewarning lamp only lights up if importantsensors fail. The Table below shows theECU’s reaction should certain faultsoccur.Diagnostic outputA diagnostic output can be made bymeans of diagnostic equipment, whichcan be used on all Bosch electronicautomotive systems. By applying aspecial test sequence, it is possible tosystematically check all the sensorsand their connectors, as well as thecorrect functioning of the ECU’s.

Table 1. ECU reactionsFailure Monitoring Reaction Warning Diagnosticof lamp outputCorrectionsensorsSignal range Reduce injectedfuel quantity●System- Signal range Limp-homesensors or emergency ● ●function (graded)Computer Program runtime Limp-home(self-test) or emergency ● ●functionFuel-quantity Permanent Engine shutoffactuator deviation●●AdvantagesEngine shutoffElectroniccontrol fordistributorpumps– Flexible adaptation enables optimizationof engine behavior and emissioncontrol.– Clear-cut delineation of individual functions:The curve of full-load injected fuelquantity is independent of governorcharacteristic and hydraulic configuration.– Processing of parameters which previouslycould not be performed mechanically(e.g., temperature-correctionof the injected fuel quantity characteristic,load-independent idle control).– High degree of accuracy throughoutcomplete service life due to closed controlloops which reduce the effects oftolerances.– Improved driveability: Map storageenables ideal control characteristics andcontrol parameters to be establishedindependent of hydraulic effects. Theseare then precisely adjusted during theoptimisation of the complete engine/vehicle system. Bucking and idle shakeno longer occur.– Interlinking with other electronic systemsin the vehicle leads the waytowards making the vehicle safer, morecomfortable, and more economical, aswell as increasing its level of environmentalcompatibility (e.g., glow systemsor electronic transmission-shift control).The fact that mechanical add-on units nolonger need to be accomodated, leadsto marked reductions in the amount ofspace required for the fuel-injectionpump.As already stated on Page 40, the principleof auto-ignition as applied to thediesel engine means that the enginecan only be switched off by interruptingits supply of fuel.When equipped with Electronic DieselControl (EDC), the engine is switchedoff by the injected-fuel quantity actuator(Input from the ECU: Injected fuelquantity = Zero). As already dealt with,the separate electrical engine shutoffdevice serves as a standby shutoff incase the actuator should fail.Electrical shutoff deviceThe electrical shutoff device is operatedwith the “ignition key” and is above allused to provide the driver with a higherlevel of sophistication and comfort.On the distributor fuel-injection pump,the solenoid valve for interrupting thesupply of fuel is fitted in the top of thedistributor head. With the diesel enginerunning, the inlet opening to the highpressurechamber is held open by the energizedsolenoid valve (the armature withsealing cone is pulled in). When the “ignitionswitch” is turned to “Off”, the powersupply to the solenoid is interrupted andthe solenoid de-energized. The springcan now push the armature with sealingcone onto the valve seat and close off theinlet opening to the high-pressure chamberso that the distributor plunger can nolonger deliver fuel.59

Axial-pistondistributorpumps,VE-MVSolenoid-valve-controlledaxial-piston distributorfuel-injection pumps VE-MV60ProspectsOn the electronically-controlled distributorpumps of the future, the electricalactuator mechanism with control collarfor fuel metering will be superseded by ahigh-pressure solenoid valve. This willpermit an even higher degree of flexibilityin the fuel metering and in the variabilityof the start of injection.Design and constructionThis pump is of modular design. The fieldprovendistributor injection pump can thusbe combined with a new electronicallycontrolled fuel-metering system (Fig. 1).Basically speaking, the solenoid-valvecontrolleddistributor pump’s dimensions,installation conditions, and drivetrain includingthe pump’s cam drive, are identicalto those of the conventional distributorpump. The most important new componentsare:– Angle-of-rotation sensor (in the formof an incremental angle/time system[IWZ]) which is located in the injectionpump on the driveshaft between thevane-type supply pump and the rollerring,– Electronic pump ECU, which is mountedas a compact unit on the top side ofthe pump and connected to the engineECU,– High-pressure solenoid valve, installedin the center of the distributor head.With regard to its installation and hydrauliccontrol, the timing device with pulsevalve is identical to the one in the previouselectronically-controlled distributorpump.ComponentsAngle-of-rotation sensorAngle-of-rotation detection uses thefollowing components: Sensor, sensorretaining ring on the driveshaft, and thetrigger wheel with a given tooth pitch.Detection is based upon the signalsgenerated by the sensor.The pulses generated by the sensor areinputted to the ECU where they are processedby an evaluation circuit. The factthat the sensor is coupled to the pump’sroller ring ensures the correct assignmentof the angular increment to theposition of the cam when the roller ring isrotated by the timing device.Pump ECUThe pump ECU is mounted on the upperside of the pump and uses hybrid techniques.In addition to the mechanicalloading with which it is confronted inthe vehicle's under-hood environment,the pump must also fulfill the followingassignments:– Data exchange with the separatelymounted engine ECU via the serialbus system,– Evaluation of the signal from theangle-of-rotation sensor (IWZ),– Triggering of the high-pressure solenoidvalve,– Triggering of the timing device.Maps are stored in the pump ECU whichnot only take into account the settingpoints for the particular vehicle applicationand certain engine characteristics,but also permit the plausibility of the receivedsignals to be checked. In addition,they form the basis for defining a numberof different computational values.

High-pressure solenoid valveThe high-pressure solenoid valve mustfulfill the following assignments:– Large valve cross-section for efficientfilling of the high-pressure chamber,even at very high rotational speeds,– Low weight (low moving masses), tokeep the loading of the parts to a minimum,– Short switching times to guaranteehigh-precision fuel metering, and– Magnetic forces which are powerfulenough to cope with the high pressures.The high-pressure solenoid valve is comprisedof:– The valve body,– The valve needle, and– The electromagnet with electricalconnection to the pump ECU.The magnetic circuit is concentric to thevalve. This fact permits a compact assemblycomprising high-pressure solenoidvalve and distributor head.Method of operationPrinciplePressure generation in the solenoidvalve-controlleddistributor injectionpump is based on the same principle asthat in the conventional electronicallycontrolledVE pump.Fig. 1Fuel supply and deliveryVia the distributor head and the openedhigh-pressure solenoid valve, the vanetypesupply pump delivers fuel to thehigh-pressure chamber at a pressure ofapprox. 12 bar.No fuel is delivered when the high-pressuresolenoid valve is de-energized(open). The valve’s instant of closingdefines the injection pump’s start ofdelivery. This can be located at thebottom dead center (BDC) of the cam oron the rise portion of the cam slope.Similarly, the valve’s instant of openingdefines the pump’s end of delivery. Thelength of time the valve is closed determinesthe injected fuel quantity.The high pressure generated in the highpressurechamber (the fuel from thesupply pump is compressed by the axialpiston when this is forced up by the camplate riding over the rollers of the rollerring) opens the delivery valve and thefuel is forced through the pressure lineto the injection nozzle in the nozzleholder. Injection pressure at the nozzleis 1400 bar. Excess fuel is directed backto the tank through return lines.Since there are no additional intake portsavailable, if the high-pressure solenoidvalve should fail, fuel injection stops.This prevents uncontrolled “racing” of theengine.Solenoid-valve-controlled axial-piston distributor fuel-injection pump (section)Electroniccontrol fordistributorpumpsUMK1205Y61

Start-assistsystemsStart-assist systemsSince leakage and heat losses reduce thepressure and the temperature of the A/Fmixture at the end of the compressionstroke, the cold diesel engine is more difficultto start and the mixture more difficult toignite than it is when hot. These facts makeit particularly important that start-assistsystems are used. The minimum startingtemperature depends upon the enginetype. Pre-chamber and swirl-chamberengines are equipped with a sheathedelementglow plug (GSK) in the auxiliarycombustion chamber which functions as a“hot spot”. On small direct-injection (DI)engines, this “hot spot” is located on thecombustion chamber’s periphery. Large DItruck engines on the other hand have thealternative of using air preheating in theintake manifold (flame start) or special,easily ignitable fuel (Start Pilot) which issprayed into the intake air. Today, the startassistsystems use sheathed-elementglow plugs practically without exception.Sheathed-elementglow plugThe sheathed-element glow plug’s tubularheating element is so firmly pressed intothe glow-plug shell that a gas-tight seal isFig. 1formed. The element is a metal tube whichis resistant to both corrosion and hot gases,and which contains a heater (glow) elementembedded in magnesium-oxide powder(Fig. 1). This heater element comprisestwo series-connected resistors: the heaterfilament in the glow-tube tip, and the controlfilament. Whereas the heater filamentmaintains virtually constant electricalresistance regardless of temperature, thecontrol filament is made of material with apositive temperature coefficient (PTC). Onnewer-generation glow plugs (GSK2), itsresistance increases even more rapidlywith rising temperature than was the casewith the conventional S-RSK glow plug.This means that the newer GSK2 glowplugs are characterized by reaching thetemperature needed for ignition far morequickly (850 °C in 4s). They also feature alower steady-state temperature (Fig. 2)which means that the glow plug’s temperatureis limited to a non-critical level.The result is that the GSK2 glow plugcan remain on for up to 3 minutesfollowing engine start. This post-glowfeature improves both the warm-up andrun-up phases with considerable improvementsin noise and exhaust-gasemissions.Sheathed-element glow plug GSK21 Electrical connector terminal, 2 Insulating washer, 3 Double gasket, 4 Terminal pin, 5 Glow-plug shell,6 Heater seal, 7 Heater and control filament, 8 Glow tube, 9 Filling powder.621 2 3 4 5 6789UMS0685-1Y

Sheathed-element glow plugs:Temperature-time diagram1 S-RSK, 2 GSK2.Temperature°C1,1501,0509508507506500 10 20 30 40 50Time tFlame glow plugThe flame glow plug burns fuel to heatthe intake air. Normally, the injectionsystem’s supply pump delivers fuel to theflame plug through a solenoid valve. Theflame plug’s connection fitting is providedwith a filter, and a metering devicewhich permits passage of preciselythe correct amount of fuel appropriateto the particular engine. This fuel thenevaporates in an evaporator tube surroundingthe tubular heating elementand mixes with the intake air. The resultingmixture ignites on the 1,000 °C heatingelement at the flame-plug tip.Glow control unitFor triggering the glow plugs, the glowcontrol unit (GZS) is provided with apower relay and a number of electronicswitching blocks. These, for instance,control the glow duration of the glowplugs, or have safety and monitoringfunctions. Using their diagnosis functions,more sophisticated glow controlunits are also able to recognise thefailure of individual glow plugs andinform the driver accordingly. Multipleplugs are used as the control inputsto the ECU. In order to avoid voltagedrops, the power supply to the glowplugs is through suitable threaded pinsor plugs.12sUMS0688EFig. 2Functional sequenceThe diesel engine’s glow plug and starterswitch, which controls the preheatand starting sequence, functions in asimilar manner to the ignition andstarting switch on the spark-ignition (SI)engine. Switching to the “Ignition on”position starts the preheating processand the glow-plug indicator lamp lightsup. This extinguishes to indicate thatthe glow plugs are hot enough for theengine to start, and cranking can begin.In the following starting phase, the dropletsof injected fuel ignite in the hot, compressedair. The heat released as a resultleads to the initiation of the combustionprocess (Fig. 3).In the warm-up phase following a successfulstart, post-heating contributesto faultless engine running (no misfiring)and therefore to practically smokelessengine run-up and idle. At the sametime, when the engine is cold, preheatingreduces combustion noise. Aglow-plug safety switchoff preventsbattery discharge in case the enginecannot be started.The glow-control unit can be coupledto the ECU of the Electronic DieselControl (EDC) so that informationavailable in the EDC control unit can beapplied for optimum control of the glowplugs in accordance with the particularoperating conditions. This is yet anotherpossibility for reducing the levels of bluesmoke and noise.Fig. 3Typical preheating sequence1 Glow-plug and starter switch, 2 Starter,3 Glow-plug indicator lamp, 4 Load switch,5 Glow plugs, 6 Self-sustained engine operation,t v Pre-heating time, t S Ready to start,t N Post-heating time.12345t V t S t N6 Time tUMS0667-1ESheathedelementglow plugs,Flameglow plugs63

The ProgramOrder NumberGasoline-engine managementEmission Control (for Gasoline Engines) 1 987 722 102Gasoline Fuel-Injection System K-Jetronic 1 987 722 159Gasoline Fuel-Injection System KE-Jetronic 1 987 722 101Gasoline Fuel-Injection System L-Jetronic 1 987 722 160Gasoline Fuel-Injection System Mono-Jetronic 1 987 722 105Ignition 1 987 722 154Spark Plugs 1 987 722 155M-Motronic Engine Management 1 987 722 161ME-Motronic Engine Management 1 987 722 178Diesel-engine managementDiesel Fuel-Injection: An Overview 1 987 722 104Diesel Accumulator Fuel-Injection SystemCommon Rail CR 1 987 722 175Diesel Fuel-Injection SystemsUnit Injector System / Unit Pump System 1 987 722 179Radial-Piston Distributor Fuel-InjectionPumps Type VR 1 987 722 174Diesel Distributor Fuel-Injection Pumps VE 1 987 722 164Diesel In-Line Fuel-Injection Pumps PE 1 987 722 162Governors for Diesel In-Line Fuel-Injection Pumps 1 987 722 163Automotive electrics/Automotive electronicsAlternators 1 987 722 156Batteries 1 987 722 153Starting Systems 1 987 722 170Electrical Symbols and Circuit Diagrams 1 987 722 169Lighting Technology 1 987 722 176Safety, Comfort and Convenience Systems 1 987 722 150Driving and road-safety systemsCompressed-Air Systems for CommercialVehicles (1): Systems and Schematic Diagrams 1 987 722 165Compressed-Air Systems for CommercialVehicles (2): Equipment 1 987 722 166Brake Systems for Passenger Cars 1 987 722 103ESP Electronic Stability Program 1 987 722 177Technical InstructionGasoline-engine managementME-MotronicEngine Managementæ ÆTechnical InstructionEngine management for spark-ignition enginesSpark Plugsæ ÆTechnical InstructionTechnical InstructionEngine management for spark-ignition enginesEmission Controlæ ÆElectronic engine management for diesel enginesDiesel Acumulator Fuel-InjectionSystem Common Railæ ÆESP Electronic Stability ProgramVehicle safety systems for passenger carsAutomotive electric/electronic systemsSafety, Comfort andConvenience SystemsEngine management for diesel enginesRadial-Piston DistributorFuel-injection Pumps Type VRAutomotive Electric/Electronic SystemsTechnical InstructionTechnical InstructionLighting TechnologyBrake systems for passenger carsBrake SystemsTechnical Instructionæ Ææ Ææ ÆTechnical InstructionTechnical Instructionæ Ææ Æ1 987 722 164KH/PDI-04.99-En(4.0)