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Home >> Pontiac >> 2009 >> Vibe Base, 2.4 0, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 64 (Engine Control System & Fuel System - 4.6L - Troubleshooting & Diagnosis) >> Fuel System Diagnosis >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
    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, 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 384-425 kPa (55-62 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 strainer
      • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
  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 (With CH 48027) or Fuel Pressure Relief (Without CH 48027) .
      2. Install the J 37287:  Adapter between the fuel feed pipe and the fuel rail.
      3. Open the valve on the J 37287:  Adapter
      4. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the CH 48027:  Gage.
      5. Command the fuel pump relay ON and then OFF with a scan tool.
      6. J 37287:  Adapter
      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 injectors.
        • If the fuel pressure does not decrease more than 34 kPa (5 psi) within the specified time, replace the 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 primary fuel pump module.
  4. Remove the J 37287:  Adapter and the CH 48027:  Gage. Refer to Fuel Pressure Gage Installation and Removal
  5. 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 primary fuel pump module.
      • Restricted fuel feed pipe
      • Restricted or plugged strainer
      • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections
  6. If the fuel system tests normal, refer to Symptoms - Engine Controls .
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