Fuel Check/Safety Valve (CNG): Service and Repair

CNG High Pressure Shutoff Valve Replacement

Special Tools

J-45878 - Combustible Gas Detector

For equivalent regional tools, refer to Special Tools Tools and Equipment.

Venting Procedure

Note:
Only compressed natural gas (CNG) Trained Technicians should attempt this service procedure. Contact General Motors TAC for information and assistance with the following procedures.

1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle Service and Repair.

2. Remove the fuel tank cover. Refer to Compressed Natural Gas Tank Cover Replacement - Aft Tank Compressed Natural Gas Tank Cover Replacement - Aft Tank , Compressed Natural Gas Tank Cover Replacement - Cargo Tank Compressed Natural Gas Tank Cover Replacement - Cargo Tank , and Compressed Natural Gas Tank Cover Replacement - Midship Tank Compressed Natural Gas Tank Cover Replacement - Midship Tank.

3. Remove the clear plastic vent cover from the cargo tank valve. Do not discard. Replace if damaged.

4. Close all manual shut-off valves. The "Closed" position is achieved by rotating manual shut-off valve clockwise until seated.





5. Relieve the CNG fuel system pressure. Refer to Compressed Natural Gas Fuel Pressure Relief (With CH-48027) Service and Repair.

6. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection Battery Negative Cable Disconnection and Connection.





7. Loosen the high pressure fuel line fitting at the CNG 1/4 turn valve several turns to allow residual system pressure to be released.

8. Completely disconnect both fuel line fittings from the 1/4 turn valve so as the fuel line can be moved away from the mating fitting by hand.





9. Remove the 1/4 turn valve locknut and remove the 1/4 turn valve handle.

10. Remove the 1/4 turn valve.

Installation Procedure

Caution:
Refer to Fastener Caution Fastener Caution.

1. Install New 1/4 turn valve on HPR bracket using new locknut. Tighten to spec.

2. Install red handle and tighten allen set screw. Tighten to spec.

3. Connect 1/4 turn valve inlet and outlet fuel lines using New O-rings. Lubricate New O-rings with petroleum jelly or equivalent before installation.

4. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection Battery Negative Cable Disconnection and Connection.

5. Install the fuel tank cover. Refer to Compressed Natural Gas Tank Cover Replacement - Aft Tank Compressed Natural Gas Tank Cover Replacement - Aft Tank , Compressed Natural Gas Tank Cover Replacement - Cargo Tank Compressed Natural Gas Tank Cover Replacement - Cargo Tank , and Compressed Natural Gas Tank Cover Replacement - Midship Tank Compressed Natural Gas Tank Cover Replacement - Midship Tank.

6. Start the vehicle and inspect for CNG fuel leaks at the serviced fittings with the J-45878 - detectoror an equivalent leak detector.