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Removing CGN Cylinder Tank

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  • Removing CGN Cylinder Tank

    Hi I have just recently purchased a vehicle equipped with CGN system. It is a 2001 Ford F150 Bi-fuel truck. My questions are: I would like to replace the tank in it since it is past it's expiration and would like to know if there is some place online that I can get instructions on how to manually shut off the cgn tank so I can safely remove the old one from the bed of the pickup truck? I can not see any shutoff at the tank itself.

  • #2
    Welcome to CNGchat!

    Thanks for doing the right thing by replacing the expired tank.

    Well, there is an easy and relatively safe first part to this procedure, followed by a more difficult and dangerous part:

    The tank likely has an electronic solenoid valve made by GFI at the neck, and is energized when the key is turned on. You will hear a "clunk" when this happens. Assuming the valve is operational you should consume as much fuel out of the tank as possible until the truck dies on CNG. At this point the tank should have less than 300 psi in it. I say "should" because you can't be 100% certain: for example a rapid depletion of fuel could cause icing in the gas, stopping the flow, and causing you to think it is at low pressure when it really isn't. But if the fuel gauge on the dash is working properly and you have seen it go down to empty and then the truck is out of fuel then you are probably OK.

    But now comes the difficult and potentially dangerous part...

    You need to vent the tank of its contents. Your truck will have a 1/4 turn high pressure shutoff valve as described in the instructions in the video "De Fueling CNG Vehicles" here:

    Note you will need to construct a grounded vent stack... so this is not a trivial exercise. I know the technician who created the above video and he could possibly send one out to you, let me know via PM.

    Also, I'm assuming your GFI valve is operational. If not, the venting must be done according to this procedure, including a special tool:

    Be safe, and let us know how you get along.