Tools Required

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. Remove the fuel tank cover. Refer to Fuel Tank Cover Replacement .
2. Relieve the CNG fuel system line pressure. Refer to Fuel Pressure Relief .

Caution: Always use the J 42435-B Compressed Natural Gas (CNG) Fuel Tank Venting Kit in conjunction with the General Motors approved Fuel Tank Venting service procedure to vent CNG fuel tanks. Failure to use the J 42435-B and follow the approved Fuel Tank Venting procedure could result in death, serious injury or vehicle and component damage.

The J 42435-B is required for the following reasons:

•	Natural gas fuel vapor can also contain water vapor.

•	The pressure drop associated with venting high pressure gaseous fuel can cause fuel vapor, tank and line temperatures to reach -73°C (-100°F) or colder.

•	The below freezing temperature can cause the water vapor to freeze

•	The J 42435-B vent hose contains an orifice which is intended to freeze before the CNG high pressure lock-off (HPL) tank valve freezes.

•	The J 42435-B pressure gauge can indicate a restricted orifice if fuel flow ceases.

•	Internal fuel tank ice build-up may result when venting the CNG fuel tank without the J 42435-B.

-	Internal fuel tank ice build-up can completely restrict the venting of fuel.

-	Venting may cease indefinitely depending upon ambient temperature conditions.

-	The ceasing of fuel tank venting may falsely indicate that the fuel tank pressure has been completely vented.

-	CNG fuel tanks with exceptionally high water content are suceptible to internal fuel tank ice build-up even with the use of the J 42435-B.

The CNG fuel tank is completely vented when all of the following conditions have been met:
1. Venting natural gas is no longer audible from the vent stack.
2. Close the J 42435-B ¼-turn valve and stabilize the fuel tank and line assembly at a temperature greater than 7°C (45°F) for at least 4 hours.

If the ambient temperature is less than 7°C (45°F), warm the fuel tank and vent line assembly manually, either with warm water or by placing the tank and line assembly into a warm environment.

3. The J 42435-B pressure gauge indicates 0 kPa (0 psi).
3. Vent the internal CNG fuel pressure from the tank. Refer to Fuel Tank Venting .

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. Disconnect the negative battery cable.
5. Remove the tank vent cover nuts and the cover. Discard the nuts.
6. Disconnect the three electrical connectors from the HPL.



7. Loosen the fill valve boot clamp and peel back the boot.
8. Disconnect the fill line at the fill valve.



9. Loosen the clamp at the tank vent boot and peel back the boot to expose the union.
10. Disconnect the fill line at the HPL and remove the line.
11. Disconnect the HPL to HPR fuel line at the HPL.
12. Disconnect the PRD at the HPL.



13. Remove the trunk trim panel.
14. Remove the cargo net, the cargo net knobs and the left wheelhouse carpet.
15. Remove the fuel fill line from the fill valve to the union.
16. Lower the rear seat.
17. Loosen the vent hose clamps at the tank and the HPR.



18. Pull the vent hose from the HPR.
19. Disconnect the HPL to HPR fuel line at the HPR.
20. Disconnect the PRD from the HPR mounting ring.
21. Remove the lines and the vent hose as an assembly.



22. Disconnect the J 42435-B vent hose from the HPL.
23. Remove the manual vent tool and all fittings.
24. Remove the fuel inlet fitting from the HPL and discard the O-rings.
25. Remove the fuel outlet fitting from the HPL and discard the O-rings.
26. Remove the HPL PRD fitting from the HPL and discard the O-rings.
27. Using the J 43602 HPL Crowfoot removal tool, loosen the HPL.



28. Remove the spare tire bracket.



29. Mark the tank in two places approximately 180 degrees apart for reference.



30. Remove the tank strap nuts and bolts and retain them.



31. Remove the clevis and bridge pins.



32. Remove the tank straps.
33. Position the J 43133 CNG Tank Remover into the tank strap bolt holes.



34. Loop the J 43133 straps around the tank and secure the straps to the tool.



35. Pull back the J 43133 in order to pull the tank free from the bracket.



36. Pull back on the straps in order to roll the tank to the upper level of the J 43133 .



37. Use a lifting device and the J 45529 CNG Tank Sling in order to remove the tank from the vehicle.
38. Unscrew and remove the HPL and the O-ring from the tank.

Tools Required

1. Install a NEW O-ring on the HPL.
2. Lubricate the O-ring with petroleum jelly.
3. Install the HPL in the tank and tighten hand-tight.
4. Lower the tank onto the J 43133 CNG tank Remover using a lifting device and the J 45529 CNG Tank Sling.
5. Roll the tank to the proper position using the orientation marks.
6. Raise the J 43133 and roll the tank into the tank cradle.



7. Remove the J 43133 from the tank bracket.
8. Install the tank straps.
9. Install the tank strap bridge pins and clevis pins.



10. Install the OLD tank strap nuts and bolts.

Tighten
Tighten the OLD tank strap nuts to 48 N·m (35 lb ft).




11. Tighten the HPL as specified below.

Tighten
Tighten the HPL to a nominal torque of 305 N·m (225 ft lb) at 0 degree. You must compensate for your torque wrench and the HPL crowfoot. Refer to the formula below for compensation of your torque wrench.

Important: Ensure the J 43602 HPL Crowfoot removal tool is straight (0 degree) on the torque wrench.

12. To obtain your Dial reading perform the following:

•	Multiply your torque wrench length in inches by 305 (225).

•	18 inch torque wrench example: 18 X 305 = 5490.

•	Add three to the length of your torque wrench.

•	18 inch torque wrench example: 18 + 3 = 21.

•	Divide the first value obtained by the second value obtained. The result will indicate the amount of torque your wrench should tighten the HPL to.

•	18 inch torque wrench example: 5490 divided by 2  = 261.4.

•	For an 18 inch long torque wrench you would tighten the HPL to 261.4 N·m.




13. Remove the OLD tank strap nuts and bolts and discard them.
14. Verify the alignment of the HPL inlet port. The fitting should be at the 3 o'clock position. Adjust the tank as necessary.



15. The tank should be located 10.5 inches from the left edge of the left tank strap. Adjust the tank as necessary.



16. Install NEW tank strap bolts and nuts.

Tighten
Tighten the tank strap nuts to 48 N·m (35 lb ft).




17. Install the vent boot.

Tighten
Tighten the vent boot clamp to 2 N·m (18 lb in).

18. Install the fuel outlet fitting (1) into the HPL using a NEW O-ring. Lubricate the O-ring with petroleum jelly.

Tighten
Tighten the fitting to 27 N·m (20 lb ft).

19. Install the fuel inlet fitting (3) into the HPL using a NEW O-ring. Lubricate the O-ring with petroleum jelly.

Tighten
Tighten the fitting to 48N·m (35 lb ft).

20. Install the FPS (2) into the HPL using a NEW O-ring. Lubricate the O-ring with petroleum jelly.

Tighten
Tighten the fitting to 27 N·m (20 lb ft).

21. Install the relief port fitting (4) into the HPL using a NEW O-ring. Lubricate the O-ring with petroleum jelly.

Tighten
Tighten the fitting to 48 N·m (35 lb ft).




22. Install the PRD and the HPL to HPR lines as an assembly.
23. Connect the PRD and HPL to HPR lines using NEW O-ring face seals. Lubricate the O-rings with petroleum jelly.

Tighten
Tighten the PRD fitting to 37 N·m (27 lb ft)

Tighten
Tighten the HPL to HPR fuel line fittings to 24 N·m (18 lb ft).

24. Install the fill valve to union fill line using NEW O-ring face seals. Lubricate the O-rings with petroleum jelly.

Tighten
Tighten the fill line fittings to 37 N·m (27 lb ft).

25. Install the union to HPL fill line using NEW O-ring face seals. Lubricate the O-rings with petroleum jelly.

Tighten
Tighten the fill line fittings to 37 N·m (27 lb ft).

Caution: The high pressure lock-off solenoid seal is more likely to leak at a lower fuel pressure. Always perform the fuel leak procedure exactly as specified. Failure to follow the proper procedures may result in serious injury or damage to the vehicle or part.

26. Fuel the vehicle in three stages at the following pressures:

25.1.

500 psi

25.2.

1500 psi

25.3.

3000 psi

27. Using the J 41416 Ultasonic Leak Detector inspect for fuel leaks at the HPL at EACH pressure.
28. Connect the electrical connectors and the HPL power connector.
29. Connect the negative battery cable.
30. Start and operate the engine on CNG.
31. Inspect for fuel leaks at each serviced fitting using the J 41416 .
32. Position the four hose clamps at the vent boot, the vent hose and the fill valve boot.

Tighten
Tighten the hose clamps to 2 N·m (18 lb in).

33. Instal the vent boot cover using NEW cover nuts.

Tighten
Tighten the NEW vent boot cover nuts to 6 N·m (54 lb in).

34. Install the left side trunk carpet.
35. Install the cargo net knobs and the cargo net.
36. Install the trunk trim.
37. Attach the information label supplied with the replacement HPL in a visible location on the head of the tank.
38. Install the spare tire bracket and spare tire bracket bolts.

Tighten
Tighten the spare tire bracket bolts to 27 N·m (20 lb ft).

39. Install the tank cover. Refer to Fuel Tank Cover Replacement .