Fuel Delivery System

The fuel metering system is made up of the following parts:
^ The fuel injectors.
^ The throttle body.
^ The fuel rail.
^ The fuel pressure regulator.
^ The PCM.
^ The crankshaft position sensor.
^ The camshaft position sensor.
^ The Idle Air Control (IAC) valve.
^ The fuel pump.
^ The fuel pump relay.

The fuel metering system starts with the fuel in the fuel tank. An electric fuel pump, located in the fuel tank with the gauge sending unit, pumps fuel to the fuel rail through an in-pipe fuel filter. The fuel pump is designed to provide fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator in the fuel rail keeps fuel available to the fuel injectors at a constant pressure. Unused fuel is returned to the fuel tank by a separate pipe.

When the key is first turned ON the PCM energizes the fuel pump relay for two seconds to build up the fuel pressure quickly. If the engine is not started within two seconds, the PCM shuts the fuel pump OFF and waits until the engine is cranked. When the engine is cranked and the RPM signal has been detected by the PCM, the PCM supplies 12 volts to the fuel pump relay to energize the electric in-tank fuel pump.

The accelerator control system is cable-type. There are no linkage adjustments. Therefore, the specific accelerator control cable must be used.

The throttle body has a throttle plate to control the amount of air delivered to the engine. The Throttle Position (TP) sensor, Mass Air flow (MAF) sensor, and Idle air control (IAC) valve are also mounted on the throttle body.

Vacuum ports located behind the throttle plate provide the vacuum signals needed by various components. Engine coolant is directed through a coolant cavity in the throttle body to warm the throttle valve and prevent icing.






The fuel rail (4) is mounted to the top of the engine and distributes fuel to the individual fuel injectors (2). Fuel is delivered to the fuel inlet tube of the fuel rail by the fuel pipes. The fuel then goes through the fuel rail to the fuel pressure regulator (3). The fuel pressure regulator maintains a constant fuel pressure at the fuel injectors. Remaining fuel is then returned to the fuel tank. Fuel pressure can be observed using a fuel pressure gauge at the fuel pressure gauge connection (1).