Circuit/System Testing

IMPORTANT:

The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
DO NOT start the engine.

Ignition ON, engine OFF, command the fuel pump relay ON with a scan tool and observe the fuel pressure gauge while the fuel pump is operating. Verify the fuel pressure is between 395-464 kPa (57-67 psi).
- If the fuel pressure is greater than the specified range, replace the fuel pump module.
- If the fuel pressure is less than the specified range, test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump module.
  - Restricted fuel feed pipe
  - Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
Verify that the fuel pressure does not decrease greater than 34 kPa (5 psi) in 1 minute.
- If the fuel pressure decreases greater than the specified value, perform the following procedure:
  1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief (High Pressure Side) or Fuel Pressure Relief (Without CH 48027) or Fuel Pressure Relief (With CH 48027) .
  2. Disconnect the chassis fuel feed hose from the engine compartment fuel pipe. Refer to Metal Collar Quick Connect Fitting Service .
  3. Install the J 37287: Shut-Off Adapter between the chassis fuel hose and the engine compartment fuel pipe.
  4. Open the valve on the J 37287: Shut-Off Adapter.
  5. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the CH-48027: Gage.
  6. Command the fuel pump relay ON with a scan tool.
  7. Close the valve on the J 37287: Shut-Off Adapter.
  8. Monitor the fuel pressure for 1 minute.
    - If the fuel pressure does not decrease greater than 34 kPa (5 psi) within the specified time, replace the fuel pump module.
Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease greater than 14 kPa (2 psi) in 5 minutes.
- If the fuel pressure decreases greater than the specified value, replace the fuel pump module.
Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH-48027: Gage. The fuel pressure should not drop off during acceleration, cruise, or hard cornering.
- If the fuel pressure drops off, test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump module.
  - Restricted fuel feed pipe
  - Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
If the fuel system tests normal, refer to Symptoms - Engine Controls .