Fuel Pressure Release: Service and Repair
Fuel Pressure Relieving
Between the engine and the manual shut-off valve
WARNING
Compressed natural gas is flammable and highly explosive. You could be killed or seriously injured if leaking natural gas is ignited.
Stop the engine, and keep heat, sparks, and flames away.
This procedure should be done outside in a well-ventilated area or in a properly equipped CNG shop.
This procedure will allow you to safely work on any part of the fuel system downstream of the manual shut-off valve, such as fuel pressure regulator P1 or the fuel injectors.
1. Raise the vehicle on a lift.
2. Close the manual shut-off valve (A).
3. Start the engine, and let it idle. After a few minutes, the engine will stall.
4. Turn the ignition switch to LOCK (0).
Between the fuel tank and the engine
WARNING
Compressed natural gas is flammable and highly explosive. You could be killed or seriously injured if leaking natural gas is ignited.
Stop the engine, and keep heat, sparks, and flames away.
This procedure should be done outside in a well-ventilated area or in a properly equipped CNG shop.
This procedure will allow you to safely work on any part of the fuel system downstream of the fuel tank such as the fuel joint block or the manual shut-off valve.
NOTE: Make sure the manual shut-off valve is open.
1. Remove the rear seat Rear Seat Removal/Installation.
2. Disconnect the fuel subharness 6P connector (A) (this prevents the tank from supplying fuel to the system).
3. Start the engine, and let it idle. After a few minutes, the engine will stall.
4. Turn the ignition switch to LOCK (0).
Between the fuel receptacle and the fuel tank
WARNING
Compressed natural gas is flammable and highly explosive. You could be killed or seriously injured if leaking natural gas is ignited.
Stop the engine, and keep heat, sparks, and flames away.
This procedure should be done outside in a well-ventilated area or in a properly equipped CNG shop.
This procedure will allow you to safely work on any part of the fuel system between the fuel joint block and the fuel receptacle.
NOTE: Make sure the manual shut-off valve is open.
1. Remove the rear seat Rear Seat Removal/Installation.
2. Disconnect the fuel subharness 6P connector (A) (this prevents the tank from supplying fuel to the system).
3. Start the engine, and let it idle. After a few minutes, the engine will stall.
4. Turn the ignition switch to LOCK (0).
5. Remove the under floor cover (A).
6. Slowly loosen the sealing bolt (A) on the fuel joint block.
7. Turn the fuel stem assembly (B) 1/2-1 turn counterclockwise.
8. Replace the fuel stem assembly and the sealing bolt O-ring (C).
At the fuel tank (If the engine runs)
WARNING
Compressed natural gas is flammable and highly explosive. You could be killed or seriously injured if leaking natural gas is ignited.
Stop the engine, and keep heat, sparks, and flames away.
This procedure should be done outside in a well-ventilated area or in a properly equipped CNG shop.
NOTE: This procedure degrades the integrity of the fuel tank. Do it only if you are replacing the fuel tank.
1. Remove the fuel pipe duct (A), then disconnect the 2P connector (B) at the fuel tank.
NOTE:
- This step prevents the tank from supplying fuel to the system.
- The manual shut-off valve must remain open until step 5.
2. Start the engine, and let it idle for about 3 minutes.
- If the engine stalls, go to step 3.
- If the engine continues to run, go to At the fuel tank (If the fuel tank internal valve is stuck open) Service and Repair.
3. Turn the ignition switch to LOCK (0), and do the battery disconnection procedure.
4. Raise the vehicle on a lift.
5. Close the manual shut-off valve (A).
6. Disconnect the fuel supply line (B) from fuel filter A (the line coming from the manual shut-off valve).
NOTE: Always use two wrenches when removing or installing fuel line nuts.
7. Loosen the fuel supply line (C) at the manual shut-off valve, move the end of the line away from fuel filter A, then connect a fuel vent tube (D) (available from the AH special tools department) to the end of the line.
8. Attach one end of the ground wire (A) (included with the new fuel tank) to the fuel supply line. Route the other end of the ground wire into the vehicle, where it will not interfere with vehicle movement.
9. Lower the vehicle to the ground.
10. Slowly remove the manual lock-down valve (A) from the fuel line side of the fuel tank, then install a manual override vent tool (B) (available from the AH special tools department) in its place.
NOTE: Do not remove the valve (C) from the receptacle side of the fuel tank.
11. With the help of an assistant, push the vehicle outside, near a metal water pipe or a chain-link fence, where the fuel can be safely vented.
12. Attach the other end of the ground wire to the water pipe or to a chain-link fence post buried in the ground. This disperses any static electricity into the ground.
13. Using an Allen wrench, slowly turn the bolt in the manual override vent tool clockwise until the bolt stops.
14. Vent the fuel from the tank by opening the manual shut-off valve. The fuel tank is empty when the hissing stops, or when fuel cannot be felt coming from the vent pipe. Once the tank is empty, close the manual shut-off valve.
NOTE: Depending on the amount of fuel in the tank, fuel venting can take from several minutes, up to a few hours.
15. Remove the manual override vent tool, then reinstall the manual lock-down valve.
16. Reinstall the fuel line to fuel filter A with a new O-ring, then retighten the fuel line at the manual shut-off valve.
17. Do a leak inspection after replacing the fuel tank Testing and Inspection.
18. Do the battery reconnection procedure.
At the fuel tank (If the engine does not start)
WARNING
Compressed natural gas is flammable and highly explosive. You could be killed or seriously injured if leaking natural gas is ignited.
Stop the engine, and keep heat, sparks, and flames away.
This procedure should be done outside in a well-ventilated area or in a properly equipped CNG shop.
NOTE: This procedure degrades the integrity of the fuel tank. Do it only if you are replacing the fuel tank.
1. Do the battery disconnection procedure.
2. Raise the vehicle on a lift.
3. Close the manual shut-off valve (A).
4. Slowly loosen the fuel supply line nut (B) going into fuel filter A. Continue to slowly loosen the nut until it is disconnected from fuel filter A.
NOTE:
- The nut may be difficult to turn at first, because of fuel pressure in the line. The fuel eventually escapes with a hiss.
- Always use two wrenches when removing or installing fuel line nuts.
5. Loosen the fuel supply line (C) at the manual shut-off valve, move the end of the line away from fuel filter A, then connect a fuel vent tube (D) (available from the AH special tools department) to the end of the line.
6. Vent the fuel in the line between the fuel tank and the manual shut-off valve by fully opening the manual shut-off valve. The small amount of fuel in the line should vent quickly with a hissing sound. The fuel flow should stop after a few seconds.
- If the fuel flow stops within a few seconds, close the manual shut-off valve, and go to step 7.
- If the fuel flow does not stop within a few seconds, close the manual shut-off valve, then do steps 7 thru 17 of At the fuel tank (If the fuel tank internal valve is stuck open) Service and Repair.
7. Attach one end of the ground wire (A) (included with the new fuel tank) to the fuel supply line. Route the other end of the ground wire into the vehicle, where it will not interfere with vehicle movement.
8. Lower the vehicle to the ground.
9. Slowly remove the manual lock-down valve (A) from the fuel line side of the fuel tank, then install a manual override vent tool (B) (available from the AH special tools department) in its place.
NOTE: Do not remove the valve (C) from the receptacle side of the fuel tank.
10. With the help of an assistant, push the vehicle outside, near a metal water pipe or a chain-link fence, where the fuel can be safely vented.
11. Attach the other end of the ground wire to the water pipe or to a chain-link fence post buried in the ground. This disperses any static electricity into the ground.
12. Using an Allen wrench, slowly turn the bolt in the manual override vent tool clockwise until the bolt stops.
13. Vent the fuel from the tank by opening the manual shut-off valve. The fuel tank is empty when the hissing stops, or when fuel cannot be felt coming from the vent pipe. Once the tank is empty, close the manual shut-off valve.
NOTE: Depending on the amount of fuel in the tank, fuel venting can take from several minutes, up to a few hours.
14. Remove the manual override vent tool, then reinstall the manual lock-down valve.
15. Reinstall the fuel line to fuel filter A with a new O-ring, then retighten the fuel line at the manual shut-off valve.
16. Do a leak inspection after replacing the fuel tank Testing and Inspection.
17. Do the battery reconnection procedure.
At the fuel tank (If the fuel tank internal valve is stuck open)
WARNING
Compressed natural gas is flammable and highly explosive. You could be killed or seriously injured if leaking natural gas is ignited.
Stop the engine, and keep heat, sparks, and flames away.
This procedure should be done outside in a well-ventilated area or in a properly equipped CNG shop.
NOTE:
- Do this procedure when the fuel flow does not stop from the tank, even after disconnecting the fuel tank 2P connector.
- This procedure degrades the integrity of the fuel tank. Do it only if you are replacing the fuel tank.
1. Close the manual shut-off valve (A).
2. Start the engine, and let it idle. After a few minutes, the engine stalls.
3. Turn the ignition switch to LOCK (0), and do the battery disconnection procedure.
4. Raise the vehicle on a lift.
5. Disconnect the fuel supply line (B) from fuel filter A (the line coming from the manual shut-off valve).
NOTE: Always use two wrenches when removing or installing fuel line nuts.
6. Loosen the fuel supply line (C) at the manual shut-off valve, move the end of the line away from fuel filter A, then connect a fuel vent tube (D) (available from the AH special tools department) to the end of the line.
7. Attach one end of the ground wire (A) (included with the new fuel tank) to the fuel supply line. Route the other end of the ground wire into the vehicle, where it will not interfere with vehicle movement.
8. Lower the vehicle to the ground.
9. With the help of an assistant, push the vehicle outside, near a metal water pipe or a chain-link fence, where the fuel can be safely vented.
10. Attach the other end of the ground wire to the water pipe or to a chain-link fence post buried in the ground. This disperses any static electricity into the ground.
11. Vent the fuel from the tank by opening the manual shut-off valve. Let the fuel vent until the hissing stops. Keep the manual shut-off valve open.
NOTE: Depending on the amount of fuel in the tank, fuel venting can take several minutes, up to a few hours.
12. Slowly remove the manual lock-down valve (A) from the fuel line side of the fuel tank, then install a manual override vent tool (B) (available from the AH special tools department) in its place.
NOTE: Do not remove the valve (C) from the receptacle side of the fuel tank.
13. Using an Allen wrench, slowly turn the bolt in the manual override vent tool clockwise until the bolt stops. This forces the fuel tank internal valve open, ensuring that all fuel is released. Once the tank is empty, close the manual shut-off valve.
NOTE:
- If more fuel vents when you open the fuel tank internal valve, continue to vent the tank until the hissing stops, or when fuel cannot be felt coming from the vent pipe.
- If no fuel vents when you open the fuel tank internal valve, the tank is empty.
14. Remove the manual override vent tool, then reinstall the manual lock-down valve.
15. Reinstall the fuel line to fuel filter A with a new O-ring, then retighten the fuel line at the manual shut-off valve.
16. Do a leak inspection after replacing the fuel tank Testing and Inspection.
17. Do the battery reconnection procedure.