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:
- Venting natural gas is no longer audible from the vent stack.
- 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. |
- The J 42435-B pressure gauge indicates 0 kPa (0 psi).
Important:
| • | If possible, operate the vehicle on CNG until most of the fuel tank pressure has been depleted. |
| • | 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. |
| • | Venting cannot be stopped once the high pressure lock-off (HPL) tank valve has been opened with the manual vent tool. The
J 42435-B
contains a ¼ turn valve that allows the vent operation
to be paused temporarily. |
| • | 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 |
| - | Tank storage outside of the vehicle (varies by local ordinance) |
CNG Fuel Tank Removed from Vehicle
Tools Required
J 42435-B CNG Tank Vent Kit
- Relieve the CNG fuel system line pressure. Refer to
Fuel Pressure Relief.
- Remove the CNG fuel tank. Refer to
Fuel Tank Replacement .
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.
- Disconnect the negative battery cable.
- Remove the fuel pressure sensor (FPS).
- Install the plug and the cap (2) in the FPS port (1).
- Install the cap (3) on the fuel inlet fitting (4).
- 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-B 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. |
- Connect the ground strap (2) (attached to the vent hose) to the HPL and to the vent stack (earth) ground.
- Remove the manual shut-off fitting from the HPL.
- Verify that the manual vent tool is closed (allen screw backed out).
- Install the manual vent tool in the HPL.
- Slowly turn the allen screw in the manual vent tool clockwise until natural gas starts to vent. Do not leave the tank unsupervised.
- The CNG fuel tank is completely vented when all of the following conditions have been met:
| 13.1. | Venting natural gas is no longer audible from the vent stack. |
| 13.2. | 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.
| 13.3. | The
J 42435-B pressure gauge indicates 0 kPa (0 psi). |
CNG Fuel Tank Installed in Vehicle
- Relieve the CNG fuel system line pressure. Refer to
Fuel Pressure Relief.
- Remove the tank cover. Refer to
CNG Fuel Tank Cover Replacement in Body Rear End.
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.
- Disconnect the negative battery cable.
- Close the manual shut-off valve (MSV).
- Disconnect the fuel line from the engine side of the MSV.
- Connect the vent hose (1) to the MSV 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-B 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. |
- Connect the ground strap (2) (attached to the vent hose) to either the tank-to-MSV fuel line, the MSV, or the vehicle frame, and to the vent stack (earth) ground.
- Open the MSV.
- Remove the manual shut-off fitting from the HPL.
- Verify that the manual vent tool is closed (allen screw back out).
- Install the manual vent tool in the HPL.
- Slowly turn the allen screw in the manual vent tool clockwise until natural gas starts to vent. Do not leave the tank unsupervised.
- The CNG fuel tank is completely vented when all of the following conditions have been met:
| 13.1. | Venting natural gas is no longer audible from the vent stack. |
| 13.2. | 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.
| 13.3. | The
J 42435-B pressure gauge indicates 0 kPa (0 psi). |
