Diesel distributor fuel-injection pumps VE - K-Jet.org

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