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 345-414 kPa (50-60 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
- Restricted or plugged fuel filter
- Restricted or plugged strainer
- 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 5 minutes.
- 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 .
  2. Disconnect the chassis fuel feed hose from the engine compartment fuel pipe. Refer to Quick Connect Fitting Service - Metal Collar .
  3. Connect the chassis fuel feed hose to the inlet side of SA9127E-7 Fuel Pressure/Flow Adapter using the J 43937 Fuel Pressure Adapter Lines. See Special Tools .
  4. Connect the engine compartment fuel pipe to the ON/OFF valve side of the SA9127E-7 using the J 43937 . See Special Tools .
  5. Cap the pressure test port on the SA9127E-7 with the J 43936 . See Special Tools .
  6. Open the valve on the SA9127E-7 . See Special Tools .
  7. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the CH-48027-100 . See Special Tools .
  8. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
  9. Close the valve on the SA9127E-7 . See Special Tools .
  10. 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 pump 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 pump module.
Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH-48027-100 . 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 pump module.
  - Restricted fuel feed pipe
  - Restricted or plugged fuel filter
  - Restricted or plugged strainer
  - 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 .