Fuel System Diagnosis

CIRCUIT DESCRIPTION
The powertrain control module (PCM) will turn ON the in-tank fuel pump, with the ignition ON. The in-tank fuel pump will remain ON as long as the engine is cranking or running, and the PCM is receiving ignition reference pulses. If the PCM does not detect any ignition reference pulses, the PCM turns the fuel pump OFF 2 seconds after the ignition is turned ON.

The in-tank fuel pump is an electric pump that is attached to the fuel sender assembly. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. A fuel pressure regulator, located in the fuel tank, 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.

TEST DESCRIPTION

Steps 1-3:

Steps 4-10:

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 fuel feed pipe shut off adapter and the fuel pump.
11. This step determines if 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.