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 gage while the fuel pump is operating. Verify the fuel pressure is between 345-427 kPa (50-62 psi).
- If the fuel pressure is greater than the specified range, replace the fuel tank 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 tank 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 more than 34 kPa (5 psi) in 1 minute.
- If the fuel pressure decreases more than the specified value, perform the following procedure:
  1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief (With CH 48027) or Fuel Pressure Relief (Without CH 48027) .
  2. Install the J 37287 between the fuel feed pipe and the fuel rail. See Special Tools .
  3. Open the valve on the J 37287 . See Special Tools .
  4. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the CH-48027 . See Special Tools .
  5. Command the fuel pump relay ON and then OFF with a scan tool.
  6. Close the valve on the J 37287 . See Special Tools .
  7. Monitor the fuel pressure for 1 minute.
    - If the fuel pressure decreases more than 34 kPa (5 psi) within the specified time, locate and replace the leaking fuel injector(s).
    - If the fuel pressure does not decrease more than 34 kPa (5 psi) within the specified time, replace the fuel tank module.
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 tank module.
Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH-48027 . See Special Tools . 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 tank 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 .