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Home › Cadillac › 2006 › STS V › Repair and Diagnosis › Engine Performance › System › Engine Control System - 4.4L - Troubleshooting & Diagnosis › Fuel System Diagnosis › Circuit/System Testing

Circuit/System Testing

IMPORTANT:
  • Inspect the fuel system for damage or external leaks before proceeding.
  • Verify that adequate fuel is in the fuel tank before proceeding.
  1. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump relay ON with a scan tool.
  3. Turn OFF the ignition.
  4. Turn OFF all accessories.
  5. Install a J 34730-1A  . Refer to Fuel Pressure Gage Installation and Removal .
  6. Turn ON the ignition, with the engine OFF.
    7. 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.
  7. Command the fuel pump relay ON with a scan tool.
  8. Observe the J 34730-1A  with the fuel pump commanded ON. The fuel pressure should be 380-410 kPa (55-60 psi).
    • If the fuel pressure is less than 380 kPa (55 psi), inspect for a restricted fuel feed pipe, poor connections at the harness connectors and ground circuits of the fuel pump, or a faulty fuel sender assembly.
    • If the fuel pressure is more than 410 kPa (60 psi), replace the fuel sender assembly.
    9. IMPORTANT: 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.
  9. Monitor the J 34730-1A  for 1 minute. The fuel pressure should not decrease more than 34 kPa (5 psi).
    • If the fuel pressure decreases more than 34 kPa (5 psi), refer to Circuit/System Testing.
  10. Relieve the fuel pressure to 69 kPa (10 psi).
  11. Monitor the J 34730-1A  for 5 minutes. The fuel pressure should not decrease more than 14 kPa (2 psi).
    • If the fuel pressure decreases more than 14 kPa (2 psi), replace the fuel sender assembly.
  12. Remove the J 34730-1A  . Refer to Fuel Pressure Gage Installation and Removal .
  13. Operate the vehicle within the conditions to reproduce the original symptoms.
  14. Monitor the O2 and the Fuel Trim parameters with a scan tool.
    • If the scan tool parameters indicate a lean condition, inspect for a restricted fuel feed pipe, poor connections at the harness connectors and ground circuits of the fuel pump, or a faulty fuel sender assembly.
    • If the scan tool parameters do not indicate a lean condition, go to Symptoms - Engine Controls .
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