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Fuel Leaks (Inside of Engine)

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
  • If you were directed here from Fuel Return System Diagnosis, go directly to step 16. This will be performed with the same components disconnected as stated in that test.
  • If you were directed here from the Engine Cranks but Does Not Run diagnostic, go directly to step 2.
  1. Test the high pressure fuel system performance.
    1. Start and idle the engine.
    2. Command the fuel pressure to 160 MPa with a scan tool.
    3. Observe the Actual Fuel Rail Pressure parameter with a scan tool
      • If the Actual Fuel Rail Pressure parameter is within 2 MPa of commanded pressure, continue this diagnostic.
      • If the Actual Fuel Rail Pressure parameter is not within 2 MPa of commanded pressure, go to Fuel System Diagnosis - High Pressure Side .
  2. Disconnect the fuel return line (1) at the engine. Refer to Quick Connect Fitting(s) Service (Metal Collar) .
    3. Fig 1: Fuel Return Line
    GM761597Courtesy of GENERAL MOTORS CORP.
  3. Remove the air duct from the air cleaner assembly to the turbo inlet.
  4. Remove the air intake pipe. Refer to Air Intake Pipe Replacement .
  5. Remove the fuel return rubber hose of the fuel injection pump from the junction block (2). Cap the fitting on the block with a 3/8 inch rubber cap (1) to prevent fuel leakage.
    6. Fig 2: Junction Block, Leak-Off Block Banjo Bolt & Rubber Cap
    GM744233Courtesy of GENERAL MOTORS CORP.
  6. Install the J 23738-A  Vacuum Pump at the fuel return pipe.
  7. Apply 15 inches Hg of vacuum to the pipe.
    • If the vacuum holds, reinstall the disconnected components and go to step 23.
    • If the vacuum does not hold, go to step 8.
  8. Remove the generator. Refer to Generator Replacement (4.3L Engine) or Generator Replacement (4.8L, 5.3L, and 6.0L Engines) or Generator Replacement (6.6L (LB7) Engine) or Generator Replacement (6.6L (LLY) Engine) or Generator Replacement (8.1L Engine) in Engine Electrical.
  9. Disconnect the fuel return line (1) from the right front cylinder head.
    10. Fig 3: Right Front And Left Rear Cylinder Heads Fuel Return Line
    GM761695Courtesy of GENERAL MOTORS CORP.
  10. Install a black hose (1) from the J 45873  Fuel Return Volume Test Kit on to the each cylinder head return port.
    11. Fig 4: J 45873 Black Hose At Cylinder Head Return Port
    GM844173Courtesy of GENERAL MOTORS CORP.
  11. Install the J 23738-A  onto each black hose and apply 15 inches Hg of vacuum to each port and record if each side holds vacuum.
  12. Perform the lower valve cover removal procedure for the bank(s) that did not hold vacuum. Refer to Valve Rocker Arm Cover Replacement - Lower Right and Valve Rocker Arm Cover Replacement - Lower Left in Engine Mechanical - 6.6L. Then go to step 13.
    13. NOTE: Refer to Fastener Notice in Cautions and Notices.
    IMPORTANT: When the fuel injector pressure lines are removed, debris will fall into the fuel injector inlet fitting. Vacuum the debris from the inlet fitting of the fuel injector before reconnecting fuel lines to the fuel injectors.
  13. Connect the fuel return lines on both cylinder heads.

    Tighten:  Tighten the bolts to 15 N.m (11 lb ft).

  14. Install the J 42964-1  3/8 Fuel Pipe Shut-Off Valve (2) to the fuel return line (1).
    15. Fig 5: Fuel Pipe Shut-Off Valve & Fuel Return Line
    GM820461Courtesy of GENERAL MOTORS CORP.
  15. Install the J 35800-A  Fuel Injector Cleaner on the J 42964-1  port closest to the fuel return line.
  16. Ensure that the shutoff valve is closed.
  17. Add 10 ounces of diesel fuel and 4 ounces of oil dye to the J 35800-A  .
  18. Connect the shop air supply to the J 35800-A  .
  19. Adjust the pressure regulator on the J 35800-A  to 15 psi.
  20. Clean the fuel injectors and fuel return lines with brake cleaning solvent and let dry.
  21. Open the valve on the bottom of the J 35800-A  canister.
  22. Inspect for leaks around the fuel injectors and the spill lines with aJ 28428-E  High Intensity Black Light Kit. Then go to step 30.
  23. Remove both upper valve covers. Refer to Valve Rocker Arm Cover Replacement - Upper Left and Valve Rocker Arm Cover Replacement - Upper Right in Engine Mechanical - 6.6L.
  24. Remove the engine oil fill tube on the front engine cover. Refer to Oil Fill Tube Replacement in Engine Mechanical - 6.6L.
    25. IMPORTANT: When the fuel injector pressure lines are removed, debris will fall into the fuel injector inlet fitting. Vacuum the debris from the inlet fitting of the fuel injector before reconnecting fuel lines to the fuel injectors.
  25. Install the fuel injector feed pipes.

    Tighten:  Tighten the fuel feed pipes to 44 N.m (32 lb ft).

  26. Add 8 ounces of oil dye to the fuel tank. On dual tank systems add the dye to the front, or primary, tank. Refer to Fuel System Description .
    27. IMPORTANT: During this test the fuel dye may quickly dilute in the engine oil. Observe the internal fuel components for dye traces immediately after start-up.
  27. Start the engine.
  28. Increase the fuel pressure to 160 MPa with a scan tool.
  29. Inspect for leaks around the fuel injectors and the fuel injection pump drive gear with a J 28428-E  . Then go to step 30.
  30. Tighten or replace any leaking components or gaskets.
  31. Perform the lower valve cover installation procedures as necessary. Refer to Valve Rocker Arm Cover Replacement - Lower Left and Valve Rocker Arm Cover Replacement - Lower Right in Engine Mechanical - 6.6L.
  32. Retest the system for engine oil dilution by performing the following procedure:
    1. Drain the engine oil from the crankcase and refill.
    2. Run the engine at idle for 10 minutes.
    3. Stop the engine and wait 10 minutes, then check the oil level on the Dip Stick. This will be the initial oil level.
    4. Run the engine at idle for 5 minutes while commanding the fuel pressure to 160 MPa with a scan tool.
    5. Stop the engine and wait 10 minutes, then check the oil level on the Dip Stick.
      • If the engine oil level is not more than 3/16 inch above the initial oil level, the system is OK.
      • If the engine oil level is more than 3/16 inch above the initial oil level, go to step 31.F.
    6. Run the engine at idle again for 5 minutes while commanding the fuel pressure to 160 MPa with a scan tool.
    7. Stop the engine and wait 10 minutes, then check the oil level on the Dip Stick.
      • If the engine oil level is not more than 3/16 inch above the last oil level, the system is OK.
      • If the engine oil level is more than 3/16 inch above the last oil level, go back to step 1.
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