Jeep Engines - Oljeep

76 MOPAR PERFORMANCE PARTSFuel Delivery and Fuel Injection SystemsNote: Older, carbureted versions of the 2.5L engine will not be discussed in this chapter. However, service parts for theseolder carbureted models are still available through your local Chrysler-Plymouth-Dodge-Jeep dealer. If you have an old 2.5Lcarbureted engine, refer to the ‘Induction System’ section of Chapter 7, 360 AMC V-8, for general carburetor information, aswell as the correct service manual for your vehicle/engine.MULTI-POINT FUEL INJECTION (MPI) SYSTEMNewer 2.5L engines use a sequential Multi-Point FuelInjection (MPI) system (vehicle specific -refer to yourservice manual). Fuel is injected into the intake manifoldbefore the intake valve in precise metered amounts throughelectrically operated injectors. The injectors are fired in aspecific sequence by the Powertrain Control Module (PCM).The PCM constantly adjusts the amount of fuel injected tomeet changing operating conditions by controlling injectorpulse width (the length of time the injector is energized). ThePCM also adjusts ignition timing by controlling the ignitioncoil operation through the Ignition Control Module (ICM).The PCM determines air-fuel mixture and ignition timingbased on inputs it receives from various sensors that monitorengine operating conditions.The PCM receives inputs from sensors that react to exhaustgas oxygen content, coolant temperature, manifold absolutepressure, engine speed (crankshaft position), throttleposition, battery voltage, intake manifold air temperature,engine knock and transmission gear selection. These inputsrepresent the engine’s instantaneous operating conditions.Air-fuel mixture and ignition timing calibrations forvarious driving and atmospheric conditions are preprogrammedinto the PCM. The PCM monitors andanalyzes its various inputs, computes engine fuel andignition timing requirements based on these inputs, andcontrols fuel delivery and ignition timing accordingly. TheEngine Control System is comprised of (1) the sensors andswitches that provide input to the PCM, (2) the PCM itself,and (3) the PCM outputs (engine control devices that thePCM constantly adjusts). The Engine Control Systemconsists of:Battery VoltageManifold Absolute Pressure (MAP) SensorCoolant Temperature SensorManifold Air Temperature (MAT) SensorExhaust Oxygen (02) SensorEngine Speedcrankshaft Position SensorThrottle Position SensorInjector Synchronization SignalA/C Select Signal0 A/C Request Signal0 Neutral Safety Switch0 Knock Sensor0 Fuel Pump Relay0 Fuel Injectors0 Idle Speed Stepper Motor0 B+ Latch RelayOxygen Sensor Heater RelayEGR Valve SolenoidIgnition Control ModuleShift Indicator Light (manual transmissions only)0 A/C Clutch RelayPowertrain Control Module (PCM)The Powertrain Control Module (PCM) is a digitalmicroprocessor. Air-fuel mixture calibrations for variousdriving and atmospheric conditions are pre-programmedinto the PCM. The PCM monitors and analyzes its variousinputs, computes engine fuel and ignition timingrequirements based on these inputs, and controls fueldelivery and ignition timing accordingly. As operatingconditions change, the PCM adjusts injector pulse width andignition timing for optimum performance and fuel economy.T --I -1