Fuel System Diagnosis

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

An electric fuel pump pumps the fuel through an in-line filter to the fuel meter body assembly. The pump attaches to the fuel sender assembly inside of the fuel tank. The fuel pump provides fuel pressure above what is needed by the fuel injectors. The pressure regulator keeps the fuel available to the injectors at a regulated pressure. Unused fuel returns to the fuel tank by the fuel return pipe.

TEST DESCRIPTION

Steps 1-5:

Steps 6-10:

Steps 11-18:

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 tests for a loss of fuel pressure between the shut-off adapter on the fuel feed pipe and the fuel pump.
11. This step determines 1 the fuel pressure regulator, or the fuel pump, is the cause of the low fuel pressure. If the pressure rises above the specified value, the fuel pump is OK.
13. This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.