Fuel Tank Vent: Service and Repair

FUEL TANK VENTING PROCEDURE

TOOLS REQUIRED
J 42435 CNG Tank Venting Kit

1. If possible, operate the vehicle on CNG until most of the fuel tank pressure has been depleted.
2. Remove the CNG fuel tank cover. Remove the truck body or side panel as required on ZW9 equipped vehicles in order to gain access to the HPL side of the CNG fuel tank.

IMPORTANT:
- Venting of natural gas to the atmosphere may be prohibited in some areas. Before venting the compressed natural gas (CNG) fuel tank, contact the authority having jurisdiction to ensure that all local, state and federal regulations are observed.
- Transportation of a pressurized CNG fuel tank is prohibited by law. The CNG fuel tank must be vented prior to consignment.
- Storing a pressurized CNG fuel tank outside of the vehicle may be prohibited. Contact the authority having jurisdiction prior to removing and storing a pressurized CNG fuel tank.
- A pressurized CNG fuel tank must be properly restrained and protected from unauthorized access when outside of the vehicle. Restrain the fuel tank to a shipping pallet or with the CNG fuel tank brackets from the vehicle and move to a secure area.
- Protect the tank from ultra-violet (UV) radiation and physical damage while removed from the vehicle. Inspect for damage any CNG fuel tank that has been removed from the vehicle prior to installation. Refer to Fuel Tank Inspection (Type 4 Tank). Testing and Inspection
- Venting cannot be stopped once the high pressure lock-off (HPL) has been opened with the manual vent tool.
- Venting the CNG fuel tank with the manual vent tool will damage the HPL. Venting the internal tank pressure is only necessary for the following:
- When required by the authority having jurisdiction
- HPL replacement
- Type 4 tank Pressure Relief Device (PRD) removal
- Internal tank cleaning
- Tank replacement
- Tank shipping
- Tank storage outside of the vehicle (varies by local ordinance)
- Vent the CNG fuel tank only while it is properly restrained within the vehicle tank brackets.

3. Relieve the CNG fuel system line pressure. Refer to Fuel Pressure Relief Procedure.
4. Disconnect the negative battery cable.




5. Close the HPL manual lock-down screw.




6. DO NOT remove the PRD (6) on a Type 4 fuel tank. The PRD must remain undisturbed until the venting procedure has been completed and you are certain that all pressure has been vented from the fuel tank.

CAUTION: The compressed natural gas (CNG) fuel tank internal pressure must be completely vented before attempting to remove the external pressure relief device (PRD). Refer to Fuel Tank Venting Procedure. Failure to perform the venting procedure could result in CNG fuel tank damage and personal injury.

7. Disconnect the fuel lines from the HPL fittings (4,8) as necessary.
8. Remove the fuel tank pressure (FTP) sensor (2).
9. Install fittings (4) supplied from the J 42435 into all of the HPL fuel ports as necessary with the exception of the PRD port (6).

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

10. Install caps supplied from the J 42435 onto the FTP port fitting (2) and the fuel outlet fitting (8) as necessary.

Tighten the caps to 37 N.m (27 lb ft).




11. Connect the female end of the vent hose to the fuel line fitting.
12. Connect the male end of the vent hose (6) to a vent stack.
13. Connect the ground strap (4) to the FTP port fitting (3) and to the vent stack earth ground (5).

CAUTION: When venting the Compressed Natural Gas (CNG) fuel tank take the following precautions in order to prevent fire and personal injury:
- Use the proper grounding procedure to an earth ground in order to prevent a build-up of static electricity which can lead to an electrical discharge.
- Use the J 42435 CNG Tank Vent Kit with a vent stack.
- Vent the CNG fuel tank in a well ventilated work area.
- Keep sparks, flames, and smoking material away from the area.
- Wear the appropriate hearing protection during the venting procedure. A sudden pressure loss from an uncontrolled gas leak can cause hearing damage.

14. Open the J 42435 1/4 turn in-line valve.
15. Ensure that the manual lock-down screw of the manual shut-off fitting (2) is open by rotating the allen screw counter-clockwise until fully seated.
16. If the tank begins venting when the manual lock-down screw is opened do not proceed to the next step until the tank stops venting.

IMPORTANT: If you were required to close the HPL manual lock-down screw during the Fuel Pressure Relief Procedure the tank may begin to vent when the lock-down screw is opened.




17. Remove the manual shut-off fitting from the HPL.
18. Obtain the manual vent tool supplied from the J 42435.
19. Rotate the screw on the manual vent tool counter-clockwise in order to fully retract the plunger prior to installation.
20. Install the manual vent tool into the HPL port ensuring that the plunger is fully retracted.

Tighten the manual vent tool to 12 N.m (108 lb in).




21. Slowly turn the manual vent tool screw clockwise until the plunger is fully extended.
22. The tank should always contain some pressure and begin to vent.
23. Allow the CNG fuel tank to vent until empty. If the tank stops venting and pressure is indicated on the J 42435 gauge, inspect the vent line for a frozen fitting. The fitting will eventually thaw and fuel will again continue to vent.

IMPORTANT: Do not leave the tank unattended during venting.

24. Inspect for freezing near the HPL. Some frost during venting is normal as the rapid pressure drop within the tank can cause internal tank temperatures to reach -73°C (-100°F). If fuel flow stops and heavy frost is evident, the HPL fitting will eventually thaw and fuel may again continue to vent.
25. The tank is vented when all of the following conditions are met:
- The HPL area and the J 42435 lines do not exhibit frost.
- The J 42435 gauge indicates 0 kPa (0 psi).
- Venting natural gas is no longer audible from the vent stack.




26. When the tank is completely vented remove the vent line (6) from the fuel fitting.
27. Remove all the fittings and caps as necessary.
28. Remove the manual vent tool (2).
29. Remove the PRD on a vehicle equipped with a Type 4 tank.
30. If the tank is to be re-used, you must replace the high pressure lock-off.
31. If the tank is to be discarded, perform the Removing From Service procedure. Refer to Fuel Tank Inspection (Type 4 Tank). Testing and Inspection