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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1558 (Engine Controls And Fuel - 3.5L (L66) - Troubleshooting & Diagnosis) >> Fuel System Diagnosis >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers in the diagnostic table.

  1. 1:  The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
  2. 3:  This step determines whether the fuel pump can provide fuel within the correct regulated pressure range.
  3. 4:  This step tests that the fuel system can maintain fuel pressure with the pump OFF. A fuel pressure drop of more than 55 kPa (8 psi) within the specified time indicates a leak in the fuel system.
  4. 6:  This step determines whether the loss in fuel pressure is on the fuel tank side of the system or the fuel rail side.
  5. 7:  This step tests the operation of the fuel pressure regulator. If the fuel pressure exceeds the specified value, the fuel pressure regulator is faulty.
  6. 8:  This step tests for a restriction in the fuel system.
Fuel System Diagnosis

Step Action Values Yes No
1  Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
IMPORTANT: Inspect the fuel system for damage or external leaks before proceeding with this diagnostic.
  1. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump relay ON with a scan tool. Refer to Scan Tool Output Controls .
Does the fuel pump operate?		 - Go to Step 3  Go to Fuel Pump Electrical Circuit Diagnosis 
3 
IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.
  1. Turn OFF the ignition.
  2. Turn OFF all accessories.
  3. Install the SA9127E  Gage Bar Set with the Fuel Pressure Adapter and the Drain Hose. Refer to Fuel Pressure Gage Installation and Removal .
  4. Turn ON the ignition, with the engine OFF.
    5. IMPORTANT: DO NOT start the engine.
  5. Command the fuel pump relay ON with a scan tool.
  6. Observe the fuel pressure gage with the fuel pump commanded ON.
Is the fuel pressure within the specified range?		 330-382 kPa (48-56 psi) Go to Step 4  Go to Step 7 
4 
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.
Monitor the fuel pressure gage for 5 minutes.Does the fuel pressure decrease by more than the specified value?		 55 kPa (8 psi) Go to Step 6  Go to Step 5 
5
  1. Operate the vehicle within the conditions to reproduce the original symptoms.
  2. Monitor the HO2S and the Fuel Trim parameters with a scan tool.
Do the scan tool parameters indicate a lean condition?		 - Go to Step 8  Go to Symptoms - Engine Controls 
6 
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Remove the fuel pressure gage from the fuel pressure test connection.
  4. Disconnect the chassis fuel hose from the engine compartment fuel pipe.
  5. Connect the fuel feed hose to the inlet side of SA9127E-7  Fuel Pressure/Flow Adapter using the J 43937  3/8 inch Male Fuel Pressure Adapter Line.
  6. Connect the return hose from the SA9127E-7  to the outlet side of SA9127E-7  .
  7. Place the other end of the return hose into the fuel filler pipe.
  8. Connect the fuel pressure gage to the SA9127E-7  .
  9. Close the valve on the SA9127E-7  .
  10. Turn ON the ignition, with the engine OFF.
  11. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
  12. Record the fuel pressure.
  13. Command the fuel pump relay OFF.
  14. Monitor the fuel pressure gage for 5 minutes.
Does the fuel pressure decrease by more than the specified value?		 55 kPa (8 psi) Go to Step 11  Go to Step 9 
7  Is the fuel pressure more than the specified value? 382 kPa (56 psi) Go to Step 11  Go to Step 8 
8 
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Remove the fuel pressure gage from the fuel pressure test connection.
  4. Raise the vehicle. Refer to Lifting and Jacking the Vehicle .
  5. Disconnect the chassis fuel feed pipe at the fuel tank pipe.
  6. Connect the inlet side of SA9127E-7  to the fuel tank pipe using the J 43937  3/8 inch Female Fuel Pressure Adapter Line.
  7. Place the return hose from the SA9127E-7  into the fuel filler pipe.
  8. Connect the fuel pressure gage to the SA9127E-7  .
  9. Open the valve on the SA9127E-7  .
  10. Turn ON the ignition, with the engine OFF.
  11. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
Is the fuel pressure more than the specified value?		 356 kPa (52 psi) Go to Step 10  Go to Step 11 
9
  1. Turn OFF the ignition.
  2. Open the valve on the SA9127E-7  .
  3. Remove the SA9127E-7  .
  4. Connect the chassis fuel hose to the engine compartment fuel pipe.
  5. Raise the fuel rail, with the fuel line connected.
  6. Turn ON the ignition, with the engine OFF.
  7. Command the fuel pump relay ON with a scan tool.
  8. Locate and replace the leaking fuel injector. Refer to Fuel Injector Replacement .
Did you complete the replacement?		 - Go to Step 12  -
10
  1. Inspect for the following conditions:
    • A blockage or restriction in the fuel feed line
    • A damaged fuel feed line
    • A blockage or restriction in the fuel rail inlet
  2. Repair the condition as necessary.
Did you complete the repair?		 - Go to Step 12  -
11 Replace the primary fuel tank module. Refer to Primary Fuel Tank Module Replacement .
Did you complete the replacement?		 - Go to Step 12  -
12 Operate the system in order to verify the repair.
Did you correct the condition?		 - System OK Go to Step 3 
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