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  • Gas tank vent

    When I put new tank in I did not have the charcoal can vent. Right know I have the 2 vent line tubes plugged. When I go to get gas and take off the gas cap there is a lot of built up pressure. What can I use for a vent, so gas doesn't leak out. Is what I am doing going to hurt anything?

  • #2
    Since I was doing a frame-up restoration, I ran a new line from the fuel tank vent up to the firewall above the transmission. I then installed a vent fitting of the type that is used for differential vent lines. All of the vent lines - diffs, tranny and fuel - are ran to the highest point of the firewall.

    I plan on installing an inline valve in the fuel vent line in case I ever end up with the rubber side up. This would hopefully prevent the gasoline from coming out of the vent.

    Also, you mentioned two vent lines. There should only be one that goes to the tank. I believe the other line is the one that went to a part-time vacuum source that would suck the fumes from the canister during engine start-up.


    • #3
      I believe 1 Liine should go to the liquid check valve then to the evaporation canistor, the 2nd line should allow any liquid from the check valve to drain back into the tank.


      • #4

        On my friends late model race car they ran a line from the fuel cell to an inline fuel filter that is mounted high in the car and that is it. This setup is in there rules as being OK. Ant thoughts?


        • #5
          The charcoal canister has 3 main jobs...

          First it provides a vent for the tank so you don'y get a pressure buildup like what you are describing. that buildup can get downright dangerous on many levels (gas spay into the eyes when trying to fill up, ruptured fuel tank in extreme cases, etc.)

          Second, the charcol canister prevents the gasoline vapors from escaping into the atmosphere by capturing them and holding them in the canister. I know you don't think that your jeep will leak that much in the way of vapors into the air, but multiply that little bit by every car in the US and it can become a problem. This is also good thing for you the driver as all it takes is one spark to light them off, or worse yet, if they get in the cab they will put Unisom to shame in real hurry.

          Third, the canister allows the engine to burn the vapors and potentially save fuel. OK, so it isn't a whole bunch of savings, but if every bit of evporated gasoline is captured and later burned, over the life of a vehicle the savings really add up.

          My vote is to restore the canister system. Once it is opperating properly, you won't even notice it is there as it does not sap any power.

          Don't think that you have to get a CJ version either, the canister off an early YJ can be made to work, or any number of other vehicles. A liitle bit of research and a haynes/Chiltons manul is all you need to get everything set up.

          Good Luck!