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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1168 (Engine Controls - 6.0L - Alternative Fuels (Introduction)) >> Repair Instructions >> High Pressure Lock-Off (HPL) Solenoid Replacement >> Removal Procedure

Removal Procedure

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    CAUTION: Do not install this part if you can not completely refill the vehicle with CNG after a repair. Failure to properly leak-check the system after the part replacement may result in serious injury, death, or damage to the vehicle or the part.
  1. Relieve the CNG fuel system pressure. Refer to Fuel Pressure Relief Procedure .
    2. CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure (Single Battery) Battery Negative Cable Disconnect/Connect Procedure (Auxiliary Battery) in Engine Electrical in the C/K Pickup service manual.
  3. Remove the fuel tank cover. Refer to Fuel Tank Cover Replacement . Remove the truck body or side panel as required on ZW9 equipped vehicles in order to gain access to the right side of the CNG fuel tank.
    4. Fig 1: Identifying HPL Line Fittings
    GM763013Courtesy of GENERAL MOTORS CORP.
  4. Disconnect the high pressure lock-off (HPL) solenoid connectors (5, 7).
    5. Fig 2: High Pressure Lock-Off (HPL) Solenoid Components
    GM790835Courtesy of GENERAL MOTORS CORP.
  5. Vent the fuel pressure from the tank. Refer to Fuel Tank Venting Procedure .
  6. Remove the vent hose (6) from the HPL.
  7. Remove the line fittings and discard the O-rings.
  8. Remove the manual vent tool.
    9. Fig 3: Loosening HPL
    GM491670Courtesy of GENERAL MOTORS CORP.
  9. With the J 43602  loosen the HPL. See Special Tools and Equipment .

    Proceed directly to Step 27 for vehicles equipped with the ZW9 option.

    10. Fig 4: Identifying High Pressure Regulator (HPR) Fuel Inlet Line
    GM762011Courtesy of GENERAL MOTORS CORP.
  10. Disconnect the high pressure regulator fuel inlet line (3).
    11. Fig 5: Identifying High Pressure Regulator (HPR) Inlet Fitting Components
    GM327075Courtesy of GENERAL MOTORS CORP.
  11. Remove the HPR fuel inlet fitting (6). Capture the filter spring (4), filter (3) and seal (2) that are located behind the inlet fitting.
    12. Fig 6: Identifying High Pressure Regulator (HPR) Components
    GM757008Courtesy of GENERAL MOTORS CORP.
    IMPORTANT: Do not hold the HPR using the HPR cover hex flange. As required wedge a wrench between the HPR and the tank frame in order to keep the HPR from spinning in the bracket.
  12. Remove the HPR mounting nut (1).
    13. Fig 7: Fuel Tank Components
    GM794992Courtesy of GENERAL MOTORS CORP.
  13. Disconnect the fuel line clips (4) at the lower tank cover mounting bracket.
  14. Disconnect the fuel line clips (3) at the tank frame (3).
  15. Remove the fuel filter mounting bolts (1).
  16. Remove the fuel filter and line assembly from the vehicle.
    17. Fig 8: Locating Upper Tank Cover Mounting Bracket Bolts
    GM763174Courtesy of GENERAL MOTORS CORP.
  17. Remove the upper tank cover mounting bracket bolts (3).
  18. Remove the upper tank cover mounting bracket (1).
    19. Fig 9: Locating Lower Tank Cover Mounting Bracket Bolts
    GM794990Courtesy of GENERAL MOTORS CORP.
  19. Disconnect the HPR coolant hoses from the lower tank cover mounting bracket retainers.
  20. Remove the lower tank cover mounting bracket bolts (2).
  21. Set aside the mounting bracket assembly in order to gain access to the tank strap retaining nuts.
    22. Fig 10: Identifying Tank Strap Retaining Components
    GM763211Courtesy of GENERAL MOTORS CORP.
  22. Remove the tank strap retaining nuts (5).
  23. Remove the tank strap upper mounting clips (6) and pins (1).
  24. Remove the tank straps from the vehicle.
    25. Fig 11: Positioning CNG Tank Support Harness
    GM763748Courtesy of GENERAL MOTORS CORP.
  25. Place the J 45529  (1) around the tank (2). See Special Tools and Equipment .
  26. Connect the J 45529  (1) to a suitable lifting device and remove the tank from the vehicle. See Special Tools and Equipment .
  27. Unthread the HPL from the CNG fuel tank and discard the HPL and O-ring.
  28. Inspect the inside of the CNG fuel tank for water, rust, or other contaminants.
  29. If necessary, clean the CNG fuel tank. Refer to Fuel Tank Cleaning .
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