Venting Procedure
Bi-Fuel/Alternative FuelsTOOLS REQUIRED
J 42435 CNG Tank Vent kit
IMPORTANT: Venting of natural gas to the atmosphere may be prohibited in some areas. Before venting the CNG fuel tank, contact the local gas company to ensure that all local, state and federal regulations are observed.
The CNG fuel tank can be vented with the tank installed in the vehicle or with the tank removed from the vehicle. The tank can also be vented if the high pressure lock-off (HPL) is non-operational.
1. Remove the CNG fuel tank cover if applicable. Refer to Fuel Tank Cover Replacement.
2. Relieve the fuel system pressure.
CAUTION: Refer to Battery Disconnect Caution in Service Precautions
3. Disconnect the negative battery cable.
4. Disconnect the fuel outlet line from the tank (if not previously disconnected). Refer to Fuel Hoses/Pipes Replacement - High Pressure Lock-Off (HPL) to High Pressure Regulator (HPR).
5. In order to prevent freeze damage to the fill line and the FPS, the tank fittings must be capped by performing the following steps:
5.1. Remove the fuel pressure sensor (FPS).
5.2. Install a fitting (1) and cap (2) supplied from the J 42435 into the FPS port.
5.3. Disconnect the fill line hose (if not previously disconnected).
5.4. Install a cap (3) supplied from the J 42435 onto the fill line port fitting (4).
6. Connect the vent hose (1) to the fuel outlet fitting and to the vent stack.
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.
7. Connect the ground strap (2) to the HPL and to the vent stack (earth) ground.
8. Connect the electronic switch box from the J 42435 to the HPL electrical connector and to the vehicle battery or a jumper battery.
IMPORTANT: If you were required to CLOSE the manual lock-down screw during the Fuel Pressure Relief Procedure the tank may begin to vent when the lock-down screw is opened.
9. Ensure the manual lock-down screw of the manual shut-off fitting is open by rotating the allen screw counter-clockwise until fully seated.
10. Energize the HPL using the electronic switch box. If the tank fails to vent due to a malfunctioning HPL proceed to Step 11. If the tank vents using the electronic switch box, proceed to Step 15.
NOTE: The manual valve opening tool can damage the main seat of the high pressure lock-off (HPL) if used improperly. Use this tool only when the HPL is not in operation.
11. Remove the manual shut-off fitting from the HPL.
12. Before installing the manual vent tool count the number of turns required to rotate the tool from fully retracted to fully extended. When venting the CNG tank ensure that you rotate the tool the same number of turns. This will ensure that the HPL pilot valve is un-seated and the tank is vented. Some pressure should always vent from the CNG tank.
Verify that the manual vent tool supplied from the J 42435 is in the non-venting position with the allen screw fully seated counter-clockwise.
13. Install the manual vent tool into the HPL port.
14. Slowly turn the manual vent tool allen screw clockwise until natural gas begins to vent.
15. Allow the CNG fuel tank to vent until the pressure gauge reads 0 kPa (0 psi). If the tank stops venting and pressure is indicated on the J 42435 CNG Tank Vent Kit gauge, inspect the vent line for a frozen fitting. The fitting will eventually thaw and fuel will again continue to vent.
Do not leave the tank unsupervised.
16. When the tank is completely vented remove the vent line from the fuel outlet fitting.
17. Remove the fitting and cap from the FPS port and the cap from the fill line port.
18. If the manual vent tool was required to vent the tank, remove the vent tool and install the manual shut-off fitting.
19. Replace the O-rings at every line and fitting location that was loosened or disconnected.
20. Tighten any loosened fittings to the correct torque. Refer to Fastener Tightening Specifications.