Fuel System Diagnosis

Fuel System Diagnosis

Circuit Description

When you turn ON the ignition switch, the control module enables the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through the fuel feed pipe to the fuel injection system. The fuel pump is an electric pump that is attached to the fuel sender assembly, which is mounted in the fuel tank. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. The fuel pressure regulator, located in the fuel tank, is attached to the fuel sender assembly. The fuel pressure regulator keeps the fuel available to the fuel injectors at a regulated pressure.

Test Description

Step 1 - Step 5:

Step 6 - Step 13:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that the fuel pump is operating.
4. This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
7. This step isolates the condition. Replace the fuel sender assembly, if the fuel pressure remains constant, after closing the valve on the fuel pipe shut-off adapter. Locate and replace the leaking fuel injector if the pressure continues to decrease after closing the valve on the adapter.
10. This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.