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Fuel Cap For Plastic Tank

Discussion in 'Early CJ5 and CJ6 Tech' started by kenb, May 7, 2022.

  1. May 7, 2022
    kenb

    kenb Cleverly disguised as a responsible adult

    Detroit
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    So I filled up my gas tank today and shortly after made a right turn. This made me realize my gas cap leaks. I have an under seat plastic tank. Should this cap have the rubber gasket? Is it the same cap as a metal under seat tank?
    IMG-20220507-WA0004.jpg
    IMG-20220507-WA0003.jpg
    Thanks,
    Ken
     
  2. May 7, 2022
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    Your cap appears to be a reproduction of the original AC/Eaton cap, and yes, there is supposed to be a flat rubber gasket to seal it to the tank.
    -Donny
     
  3. May 8, 2022
    kenb

    kenb Cleverly disguised as a responsible adult

    Detroit
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    Thanks for the reply. Any tips on a part number for a replacement? Searching around a see a lot of caps listed as "non-vented", is that appropriate for my application?
     
  4. May 8, 2022
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    Unless you have a return line, you will need a vented cap.
    -Donny
     
  5. May 8, 2022
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2022 Sponsor 2021 Sponsor

    East Tennessee
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    I have a plastic tank in one of my Jeeps and the cap I used is the same one that was on the steel tank that was in it. Mine is a Stant, it is vented, and yes it does have a gasket, but I don't know the model number.

    With a full tank most of these Jeeps will burp a little gas, it is better not to fill it to full capacity.
     
    Rick Whitson likes this.
  6. May 8, 2022
    kenb

    kenb Cleverly disguised as a responsible adult

    Detroit
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    This is a V6 application and it does have a return fuel line from the fuel pump. So I don't need a vent then? Thanks for the help
     
  7. May 8, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    The return is not a vent. Instead it circulates fuel from the tank to the pump and back to keep the fuel cooler.

    The vent is through the gas cap. You must have a vent so the fuel level can go down and more air can come in.

    In my experience, these under seat tanks will leak a little on side-hill or when there is a lot of sloshing. It helps to leave some extra room above the fuel.
     
  8. May 8, 2022
    kenb

    kenb Cleverly disguised as a responsible adult

    Detroit
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    Thanks for the replies. I ordered a replacement cap from Gates, hopefully I can just swap the gasket.
     
  9. May 8, 2022
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    If it is an MTS tank the best bet is to get a cap from MTS. None of the ones for the factory steel tanks I had fit properly whereas the MTS cap fits very well. The issue I had was the thickness of the plastic where the tabs engage the next and lock it in place. What was said above about not filling to the top.
     
  10. May 9, 2022
    Rick Whitson

    Rick Whitson Detroit Area 2022 Sponsor 2021 Sponsor 2020 Sponsor

    I live South of...
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    I have a re-popped steel tank and it's the same way, if I fill the tank and park it on a sidehill it will leak too. I leave it a little low when I fill up.
     
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