GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Chevy K Silverado - 4WD (CNG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 Fuel Hose/Pipe Replacement - Union to Low Pressure Lock-Off

Tools Required

J 45878 Combustible Gas Detector

Removal Procedure

    Caution: Natural gas is highly flammable. In order to reduce the risk of fire and personal injury, keep sparks, flames, and smoking materials away from the vehicle while you perform the Compressed Natural Gas (CNG) fuel system service.

    Caution: The Compressed Natural Gas (CNG) system operates at pressures up to 24820 kpa (3600 psi). Relieve the CNG fuel system pressure before servicing CNG fuel system components in order to reduce the risk of fire and personal injury.

  1. Relieve the fuel system pressure. Refer to Fuel Pressure Relief .

    2. Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical in the C/K Pickup service manual.
  3. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information in the C/K Pickup service manual.

    4. Object Number: 757011 Size: SH
  4. Disconnect the center fuel line (5) from the low pressure lock-off (LPL) solenoid fuel line (2).
  5. Lower the vehicle.

    6. Object Number: 756969 Size: SH
  6. Disconnect the LPL fuel line (1) from the LPL solenoid fitting (2).
  7. Remove the line from the vehicle.

Installation Procedure

    Object Number: 756969 Size: SH
  1. Install the fuel line (1) into the vehicle.

    2. Caution: Natural gas is stored under high pressure. If a leak occurs, the high pressure could cause a personal injury. In order to prevent Compressed Natural Gas (CNG) fuel leaks, always replace the CNG fuel system O-rings during service.

  2. Connect the fuel line (1) to the low pressure lock-off (LPL) solenoid fitting (2) using a new O-ring face seal. Lubricate the O-ring with petroleum jelly.

    3. Tighten
    Tighten the fuel line to 37 N·m (27 lb ft).


    Object Number: 757011 Size: SH
  3. Connect the center fuel line (5) to the LPL fuel line (2) using a new O-ring. Lubricate the O-ring face seal with petroleum jelly.

    4. Tighten
    Tighten the fuel line to 37 N·m (27 lb ft).

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  4. Install the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical in the C/K Pickup service manual.
  5. Start the vehicle and inspect for CNG fuel leaks at the serviced fitting using the J 45878 or an equivalent liquid leak detector.