Part 1 of 3

Chart A-7 - Fuel System Diagnosis (Part 1 Of 3):

Fuel Line Diagram:

Circuit Description:
When the ignition switch is turned "ON," the Powertrain Control Module (PCM) will turn "ON" the in-tank fuel pump. It will remain "ON" as long as the engine is cranking or running, and the PCM is receiving reference pulses. If there are no reference pulses, the PCM will shut "OFF" the fuel pump in about 2 seconds after ignition "ON" or engine stops.

An electric fuel pump, part of the modular fuel sender (inside the fuel tank), supplies fuel through an in-line filter to the fuel rail assembly. The pump is designed to provide sufficient fuel flow for all engine demands. A pressure regulator, attached to the fuel rail, keeps fuel available to the injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate line.

The fuel pump "test" connector is located on the driver's side of the engine compartment near the strut tower.

Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Install fuel pressure gage. Refer to Part 3 of 3 and above illustration. With ignition "ON" and fuel pump running, pressure should he 284 - 325 kPa (41 - 47 psi). This pressure is controlled by spring pressure within the regulator assembly.
2. When the engine is idling, the manifold pressure is low (high vacuum) and is applied to the pressure regulator diaphragm. Vacuum will offset spring pressure and result in a lower fuel pressure Fuel pressure at idle will vary somewhat depending on barometric pressure, but should be less than the pressure noted in Step (1).
3. A system that does not hold pressure is caused by one of the following:
^ Leaking fuel pump flex pipe.
^ Leaking check valve in flex pipe connector.
^ Leaking fuel pump upper insulator.
^ Leaking valve/seat within pressure regulator.
^ Leaking injector(s).
4. A leaking injector sticking can best be determined by checking for a fouled or saturated spark plug(s). If a leaking injector cannot be determined by a fouled or saturated spark plug, the following procedure should be used
^ Remove fuel rail but leave fuel lines connected. See "Fuel Delivery System."
^ Lift fuel rail out just enough to leave injector nozzles in the ports.

CAUTION: Be sure injector(s) are not allowed to spray on engine and that injector retaining clips are intact. This should be carefully followed to prevent fuel spray on engine which would cause a fire hazard.

^ Pressurize the fuel system and observe injector nozzles.