Fuel System Diagnosis

FUEL SYSTEM DIAGNOSIS

SYSTEM DESCRIPTION
The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within two seconds if ignition reference pulses cease to be detected and the ignition remains ON.

The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through an in-line fuel filter to the fuel injection system. The pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. A separate pipe returns unused fuel to the fuel tank.



TEST DESCRIPTION

Steps 1-2:

Step 3:

Steps 4-6:

Steps 7-9:

Step 10:

Steps 11-13:

Steps 14-15:

Step 16:

Steps 17-19:

Steps 20-25:

The numbers below refer to the step numbers on the diagnostic table.


4. This step tests for an internal fuel leak.
5. This step tests the fuel pump check valve for a leak down condition.
6. This step tests the fuel pressure regulator.
10. This step tests for a loss of fuel pressure between the fuel feed pipe shut-off adapter and the fuel pump.
11. This step tests for a leaking fuel injector or for a leaking fuel pressure regulator.
14. This step tests for a restricted fuel return pipe.
16. This step determines if the fuel pressure regulator or the fuel pump is the cause of the low fuel pressure.
18. This step verifies that a circuit condition is not the cause of a fuel pressure concern.