Fuel Tank Venting Procedure

Venting cannot be stopped once the High Pressure Lock-Off (HPL) solenoid has been opened using the manual vent tool. Venting the CNG fuel tank will damage the HPL solenoid. Venting is only necessary for high pressure lock-off replacement, internal tank cleaning, tank replacement or tank shipping.

1. Remove the CNG fuel tank shield. See FUEL TANK SHIELD . Relieve the fuel system pressure. See FUEL PRESSURE RELIEF PROCEDURE . Disconnect the negative battery cable. Disconnect the fuel outlet line from the tank. Install a cap supplied from the CNG Tank Vent Kit (J 42435) onto the fuel line fitting of the fuel outlet port. Tighten the cap.
2. If the front tank is being vented, remove the Fuel Tank Pressure (FTP) sensor and install a fitting supplied from the CNG tank vent kit into the FTP sensor port. The rear tank is already capped at this port. On either tank, disconnect the fuel inlet line from the tank. Connect the female end of the vent hose to the fuel line fitting.
3. Connect the male end of the vent hose to a vent stack. Refer to the tank vent kit container for instructions on how to properly construct a vent stack. Connect the ground strap to the FTP sensor port fitting and to the vent stack earth ground.
WARNING: 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. Ensure that the manual lock-down screw of the manual shut-off fitting is open by rotating the Allen screw counterclockwise until fully seated. If the tank begins venting when the manual lock-down screw is opened do not proceed until the tank stops venting. DO NOT leave the tank unattended during venting.
4. Remove the manual shut-off fitting from the HPL solenoid. Obtain the manual vent tool supplied from the tank vent kit. Rotate the screw on the manual vent tool counter-clockwise in order to fully retract the plunger. Install the manual vent tool into the HPL solenoid port with the plunger fully retracted. Tighten the manual vent tool. Slowly turn the manual vent tool screw clockwise until the plunger is fully extended.
CAUTION: DO NOT leave the tank unattended while venting.
5. Open the tank vent kit in-line valve if equipped. The tank should always contain some pressure and begin to vent. Allow the CNG fuel tank to vent until the pressure gauge reads 0 psi (0 kPa). If the tank stops venting and pressure is indicated on the tank vent kit gauge, inspect the vent line for a frozen fitting. The fitting will eventually thaw and fuel will again continue to vent.
6. When the tank is completely vented, remove the vent line from the fuel fitting. Remove the fitting and cap from the FTP sensor port. Remove the fuel fitting from the fuel outlet port. Remove the manual vent tool. If the tank is to be re-used, replace the high pressure lock-off. See HIGH PRESSURE LOCK-OFF SOLENOID . If both tanks require venting, repeat procedure on the other tank.