Jeep Engines - Oljeep

2.5L POWER TECH IN-LINE 4 (FUEL DELIVERY AND FUEL INJECTION SYSTEMS) 79fuel pressure on the bottom of the diaphragm is assisted byintake manifold pressure on the spring side of thediaphragm, resulting in lower system fuel pressure. Thefuel pressure regulator is not controlled by the PCM.IAIRccvRacing ModificationsBy their nature, unlike carbureted engine set-ups, fuelinjection systems deliver fuel equally among all fourcylinders. It’s because of this excellent fuel distributioncharacteristic that fuel injection is preferred over carburetors,even over high performance 2 and 4-Bbl. carburetors.And don’t disconnect those stock fuel injection sensors!Today’s engines run a lot hotter because they run a lotleaner; because of this, fuel injection temperature is verycritical. It is something that has to be constantly monitoredand stabilized to keep the fuel injection and the power levelin their proper places. Mopar Performance Partsrecommends the use of all sensors, even in highperformanceracing set-ups. These sensors constantly inputvital information to the PCM, and the PCM corrects themixture accordingly.And don’t abandon that oxygen sensor, either. Since racingset-ups don’t use catalytic converters, use an EGT probe tolocate the hottest spot in the exhaust system and install theoxygen sensor there.Crankcase Ventilation SystemAll 2.5L 4-cylinder engines are equipped with a CrankcaseVentilation (CCV) system (Figure 2-84). The CCV systemperforms the same function as a conventional PCV system,but does not use a vacuum controlled valve.A fitting on the driver’s side of cylinder head (valve)cover contains the metered orifice. It is connected tomanifold vacuum.A fresh air supply CCV tube (hose) from the air cleaner isconnected to the rear cover.When the engine is operating, fresh air enters the engine andmixes with crankcase vapors. Manifold vacuum draws thevapor/air mixture through the fixed orifice and into the intakemanifold. The vapors are then consumed during combustion.Figure 2 - 84ccv PTUBETHROTTLE BODY (SINGLE POINT) FUELINJECTION (TBI)aQa4a5d8Throttle Body Fuel Injection (TBI) is a single point, pulsetime system that injects fuel through an electricallyoperated fuel injector into the throttle body above thethrottle plate.The fuel injection pulse width (period of time that theinjector is energized causing fuel to be released into thethrottle body) is controlled be the engine’s ElectronicControl Unit (ECU). The ECU accomplishes this byopening and closing the ground path to the injector. Bycontrolling fuel injector pulse width, the ECU is able tometer the amount of fuel to the engine and constantly adjustthe air-fuel ratio.The ECU receives inputs from sensors that react to exhaustgas oxygen content, coolant temperature, manifold absolutepressure, engine speed (crankshaft position), throttleposition, battery voltage, and air-fuel temperature. Theseinputs represent the engine’s instantaneous operatingconditions. Based on these inputs, the ECU adjusts air-fuelratio and ignition timing for the current operatingconditions. The engine control system is comprised of (1)the sensors and switches that provide input to the ECU, (2)the ECU itself, and (3) the ECU outputs (engine controldevices that the ECU constantly adjusts).1- - ll ’1