Circuit/System Testing

Ignition ON, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is between 294-335 kPa (43-49 psi).
- If the fuel pressure is not within the specified range, perform one of the following procedures:
  Greater than the specified value:
  1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
  2. Disconnect the fuel return pipe from the fuel rail, and attach a length of flexible fuel hose to the fuel rail with the open end of the hose placed into an approved gasoline container.
  3. Ignition ON, monitor the fuel pressure gage while the fuel pump is operating. Verify the fuel pressure is between 294-335 kPa (43-49 psi).
    - If the pressure is within the specified range, locate and repair the restriction in the fuel return line.
    - If the pressure is above the specified range, replace the fuel pressure regulator.
  Less than the specified value:
  1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
  2. Disconnect the fuel return pipe from the fuel rail, and install the J 37287 between the fuel return pipe and the fuel rail.
  3. Open the valve on the J 37287 and bleed the air from the fuel pressure gage.
  4. Slowly close the valve on the J 37287 , while the fuel pump is operating. Monitor the fuel pressure gage.
    - If the fuel pressure increases to above 345 kPa (50 psi), replace the fuel pressure regulator.
    - If the fuel pressure remains below 345 kPa (50 psi), test for a restricted fuel feed pipe or restricted fuel filter. If the system tests OK, replace the fuel pump.

IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

Verify that the fuel pressure remains constant within 34 kPa (5 psi) for 1 minute.
- If the fuel pressure decreases more than the specified value, perform the following procedure:
  1. Inspect the fuel pressure regulator vacuum hose for fuel.
    - If fuel is found in the vacuum hose, replace the fuel pressure regulator.
  2. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
  3. Install a J 37287 between the fuel feed pipe and the fuel rail, and between the fuel return pipe and the fuel rail.
  4. Open the valves on both of the J 37287 and bleed the air from the fuel pressure gage.
  5. Close the valve on the J 37287 that is connected to the fuel feed pipe. Monitor the fuel pressure gage for 1 minute.
    - If the fuel pressure remains constant, replace the fuel pump.
  6. Ignition OFF, open the valve on the J 37287 that is connected to the fuel feed pipe.
  7. Ignition ON, close the valve on the J 37287 that is connected to the fuel return pipe. Monitor the fuel pressure gage for 1 minute.
    - If the fuel pressure remains constant, replace the fuel pressure regulator.
    - If the fuel pressure drops, locate and replace the leaking fuel injector.
Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi). in 5 minutes.
- If the fuel pressure decreases more than the specified value, replace the fuel pump.
Operate the vehicle within the conditions of the customers concern while monitoring fuel related parameters with a scan tool.
- If the scan tool parameters indicate a lean condition, test/inspect for the following:
  - Restricted fuel feed pipe
  - Restricted fuel filter
  - Faulty fuel pressure regulator
  - Poor connections at the harness connectors and ground circuits of the fuel pump
- If all test normal and the scan tool parameters indicate a lean condition, replace the fuel pump.