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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 364 (Engine Controls And Fuel - 5.3L, 6.0L & 6.2L - DTC P0443 Through DTC P3449 And Troubleshooting) >> Diagnostic Information and Procedures >> Fuel System Diagnosis (Without FPCM) >> Circuit/System Testing

Circuit/System Testing

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    NOTE:
    • 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.
  1. Ignition ON, 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 345-414 kPa (50-60 psi).
    • If the fuel pressure is greater than the specified range, replace the fuel pump.
    • If the fuel pressure is less than the specified range, remove the fuel tank and test, inspect, and repair the items listed below. If all items test normal, replace the fuel tank fuel pump module.
    • Restricted fuel feed pipe
    • Restricted or plugged fuel filter
    • Restricted or plugged strainer
    • Stuck or binding fuel level float
    • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
    2. NOTE:

    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.

  2. 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 (Without CH-48027) , Fuel Pressure Relief (CH-48027) .
    2. Install the J 37287 between the fuel feed pipe and the fuel rail.
    3. Open the valve on the J 37287 .
    4. Ignition ON, command the Fuel Pump Relay ON with a scan tool and bleed the air from the fuel pressure gauge.
    5. Close the valve on the J 37287 .
    6. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
      • If the fuel pressure drops, locate and replace the leaking fuel injector.
    7. If the fuel system test normal, replace the fuel tank fuel pump module.
  3. 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 fuel pump module.
  4. Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH-48027 Gauge. 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 primary fuel tank module.
    • Restricted fuel feed pipe
    • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections
  5. If the fuel system components test normal, refer to Symptoms - Engine Controls .
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