DELPHI EFI Tip of sensor, protruding into exhaust gas, is hollow. Outer portion of tip is surrounded by exhaust gas, with inner portion exposed to ambient air. When oxygen concentration on one side of tip is different than that of other side, a voltage signal up to 1.0 volt is generated and sent to ECU. Voltage signal tells ECU if engine is straying from ideal fuel mixture, and ECU then adjusts injector pulse accordingly. Oxygen sensor functions after being heated to a minimum of 400°C (752°F). A heater inside sensor heats electrode to optimum temperature in about 10 seconds.
Oxygen sensor receives ground through wire, eliminating QHHGIRUSURSHUJURXQGLQJWKURXJKPXIAHU,ISUREOHPV indicate a bad oxygen sensor, check all connections and wire harness. Oxygen sensor can also be contaminated by leaded fuel, certain RTV and/or other silicone compounds, fuel injector cleaners, etc. Use only those products indicated as O2 Sensor Safe. Manifold absolute pressure (MAP) sensor provides immediate manifold pressure information to ECU. MAP measures difference in pressure between outside atmosphere and vacuum level inside intake manifold and monitors pressure in manifold as primary means of detecting load.
Data is used to calculate air density DQGGHWHUPLQHHQJLQH VPDVVDLUARZUDWHZKLFKLQ turn determines required ideal fueling. MAP also stores instant barometric pressure reading when key is turned ON. Fuel injectors mount into intake manifold, and high pressure fuel line attaches to them at top end. Replaceable Orings on both ends of injector prevent external fuel leakage and also insulate it from heat and vibration. A special clip connects each injector to high pressure fuel line and holds it in place. Orings and retaining clip must be replaced any time fuel injector is separated from its normal mounting position.
When key switch is on, fuel pump module will pressurize high pressure fuel line to 39 psi, and voltage is present at injector. At proper instant, ECU completes ground circuit, energizing injector. Valve needle in injector is opened electromagnetically, and pressure in high pressure fuel line forces fuel down through inside. Director plate at tip of injector contains a series of calibrated openings which directs fuel into manifold in a coneshaped spray pattern. Injectors have sequential fueling that open and close once every other crankshaft revolution.
Amount of fuel injected is controlled by ECU and determined by length of time valve needle is held open, also referred to as injection duration or pulse width. Time injector is open (milliseconds) may vary in duration depending on speed and load requirements of engine. A highvoltage, solidstate, battery ignition system is used with EFI system. ECU controls ignition output and timing through transistorized control of primary current delivered to coils. Based on input from crankshaft SRVLWLRQVHQVRU(&8GHWHUPLQHVFRUUHFWїULQJSRLQW for speed at which engine is running.
At proper instant, LWLQWHUUXSWVARZRISULPDU\FXUUHQWLQFRLOFDXVLQJ HOHFWURPDJQHWLFAX[їHOGWRFROODSVH)OX[FROODSVH induces an instantaneous high voltage in coil secondary which is strong enough to bridge gap on spark plug. (DFKFRLOїUHVHYHU\RWKHUUHYROXWLRQ EFI engines are equipped with either a 20 or 25 amp charging system to accommodate combined electrical GHPDQGVRILJQLWLRQV\VWHPDQGVSHFLїFDSSOLFDWLRQ Charging system troubleshooting information is provided in Electrical. An electric fuel pump module and a lift pump (two types) are used to transfer fuel in EFI system. Three types of lift pumps: are a pulse fuel pump, a mechanical fuel pump, or a low pressure electric fuel pump.
Pumping action is created by either oscillation of positive and negative pressures within crankcase through a hose, or by direct lever/pump actuation off rocker arm movement. Pumping action causes diaphragm on inside of pump to pull fuel in on its downward stroke and to push it into fuel pump module on its upward stroke. Internal check valves prevent fuel from going backward through pump. Fuel pump module receives fuel from lift pump, increases and regulates pressure for fuel injectors. Fuel pump module is rated for a minimum output of 13.5 liters per hour and regulated at 270 kilo pascals (39 psi).
When key switch is turned ON and all safety switch requirements are met, ECU activates fuel pump module for about six seconds, which pressurizes system for startup. If key switch is not promptly turned to start position, engine fails to start, or engine is stopped with key switch ON (as in case of an accident), ECU switches off pump preventing continued delivery of fuel. In this situation, MIL will go on, but it will go back off after 4 cranking revolutions if system function is OK. Once engine is running, fuel pump remains on. Precision components inside fuel pump module are not serviceable. DO NOT attempt to open fuel pump module. Damage to components will result and warranty will be void.
Because fuel pump module is not serviceable, engines are equipped with a special 10micron EFI fuel їOWHUWRSUHYHQWKDUPIXOFRQWDPLQDWLRQIURPHQWHULQJ module. ,IWKHUHDUHWZRїOWHUVLQV\VWHPRQHEHIRUHOLIWSXPS ZLOOEHDVWDQGDUGPLFURQїOWHUDQGRQHDIWHUOLIW SXPSZLOOEHVSHFLDOPLFURQїOWHU%HVXUHWRXVHDQ DSSURYHGPLFURQїOWHUIRUUHSODFHPHQW High pressure fuel line is an assembly of hoses, injector caps and a fuel connector to fuel pump module. High pressure fuel line feeds fuel to top of injectors through injector caps. Caps are fastened to intake manifold and injectors are locked into place. A small retaining clip provides a secondary lock. 25 24 690 01 Rev. D KohlerEngines.com