Fuel System Diagnosis

Fuel System Diagnosis

System Description

When the ignition is turned ON, the engine control module (ECM) turns ON the in-tank fuel pump by energizing the fuel pump relay. The in-tank fuel pump remains ON as long as the engine is cranking or running and the ECM receives ignition reference pulses. If there are no reference pulses, the ECM turns the in-tank fuel pump OFF 2 seconds after the ignition is turned ON or 2 seconds after the engine stops running. The electric fuel pump is incorporated into the modular fuel pump and sender assembly design and is located inside the fuel tank. The fuel pump supplies fuel through a fuel filter, through the fuel feed pipes, and to the fuel rail assembly. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator, attached to the fuel rail, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate fuel return pipe.

Diagnostic Aids

* A hard start or long crank time when the engine is cold can be caused by low fuel pump volume.

* The fuel pressure should build quickly when the fuel pump is turned ON.

* If you must wait more than 2 seconds for the fuel pressure to build, suspect low fuel pump volume.

* For an intermittent condition, refer to Intermittent Conditions Intermittent Conditions.