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venting vs non-venting gas cap

Discussion in 'Flat Fender Tech' started by 47v6, Feb 22, 2015.

  1. Feb 22, 2015
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    My gas cap does not vent. I need to keep it cracked or my jeep pulls a vacuum and dies. I see there are non venting gas caps. How exactly does that work? A tank vent? My issue is that my fuel evaporates before I can burn it and fuel does leak out somewhat.
     
  2. Feb 22, 2015
    cj6/442

    cj6/442 Sponsor Sponsor

    Fallbrook, Calif
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    I want a non vented cap does it have any part numbers?
     
  3. Feb 23, 2015
    47v6

    47v6 junk wrecker! Sponsor

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    No, no part numbers. It looks to be an original CJ2A cap front epics i can find online. I also looked at it a little closer. it had an opening in the center of the cap and another one on the ouside of the sealing ring. obviously it is vented but clogged.
     
  4. Feb 23, 2015
    timgr

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

    Medford Mass USA
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    So this is an under-seat tank? AFAIK no non-vented caps exist for that application, unless you found one from another application that will fit. In theory, a non-vented cap will not work with that system. The fuel pump will evacuate the tank and cause fuel starvation.
     
  5. Feb 23, 2015
    47v6

    47v6 junk wrecker! Sponsor

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    yeah thats what i have. It actually IS vented but just plugged with something. I will have to clear the vent.
     
  6. Feb 25, 2015
    WorkInProgress

    WorkInProgress Member

    Kennewick, Wa
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    My opinion. Don't buy a reproduction cap. I bought a repop and it leaked gas all over my jeep at the slightest angle. Then I bought a Nos cap on ebay and no more problems
     
    Hellion and heavychevy like this.
  7. Feb 25, 2015
    68BuickV6

    68BuickV6 Well-Known Member

    Chino, CA.
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    Keep the cap plugged if it doesnt leak when wheeling radically. add a breather to the tank.

    I'd love my cap to not leak. Doubled up the seals and nearly had it, but still not it...
     
  8. Feb 25, 2015
    1955CJ-5

    1955CJ-5 Member

    Boise, Idaho
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    The original Eaton caps had four vents around the perimeter, and a ball valve inside that was supposed to prevent leaking......I used spray brake cleaner to clear the vents, but the ball valve doesn't really work that well....

    [​IMG]
     
  9. Feb 25, 2015
    Patrick

    Patrick Super Moderator Staff Member Sponsor

    Los Alamos, NM
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    I use a non-vented cap (I got one last week from NAPA) and I add a vent line from the filler neck. Did it this way on my CJ5, and just did it on the 2A when I installed the new tank. No leaks, works perfectly.
     
  10. Feb 25, 2015
    47v6

    47v6 junk wrecker! Sponsor

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    mine has a hole in the center and a hole on the other side of the seal on the outside of the seal area where it contacts the tank. It is obviously plugged. It might be easier to just vent the tank using one of the screws for the sender cover. I had to run a return for my fuel pump that I plumbed into my tank.
     
    Last edited: Feb 25, 2015
  11. Feb 25, 2015
    68BuickV6

    68BuickV6 Well-Known Member

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    Got a part #? How off camber can you get without leaking?
     
    Last edited by a moderator: Feb 25, 2015
  12. Feb 25, 2015
    Patrick

    Patrick Super Moderator Staff Member Sponsor

    Los Alamos, NM
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    Until the Jeep is about to go over I reckon..I'll have to see if the box from the cap is still in the trash...I just had NAPA look it up for my 48 CJ2A, but it's the same cap that fits all the under seat tanks
     
  13. Feb 25, 2015
    Patrick

    Patrick Super Moderator Staff Member Sponsor

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  14. Feb 26, 2015
    68BuickV6

    68BuickV6 Well-Known Member

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    Thank you.
     
  15. Feb 26, 2015
    Patrick

    Patrick Super Moderator Staff Member Sponsor

    Los Alamos, NM
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    I can get some pics of my vent line tomorrow. It runs from the filler neck, up under the tub lip (inside the tub) near the roll bar, loops back and terminates at a fitting in the filler well in front of the filler neck.
     
  16. Feb 26, 2015
    timgr

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

    Medford Mass USA
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    If your cap does not leak, I'd suggest you keep it and fit a vent. Not surprised that the OEM caps work better.

    Back when I had my '73 CJ-5, I bought all-new parts from the dealership where I worked to put a tank under the driver's seat. The cap we stocked came in a Stant box, not Jeep packaging. When I asked about that, the parts ordering lady said they were much cheaper from local AP warehouse than from Jeep. They were then selling them for the Jeep list price. Of course, it leaked.
     
  17. Feb 26, 2015
    47v6

    47v6 junk wrecker! Sponsor

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    Might leak, i haven't had it at an able yet to notice. i would like to remedy that angle problem to see if i can get it to leak. I will be installing a tank vent as soon as i see what Mr. Patricks looks like.
     
  18. Feb 26, 2015
    achuto

    achuto New Member

    Vista,...
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  19. Feb 26, 2015
    Patrick

    Patrick Super Moderator Staff Member Sponsor

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    I should add, I did put a slightly thicker gasket in the Napa cap. .on my cj5 I used a cap made by MTS. It still seals to this day. I ordered one for my cj2a (MTS) and it was junk. Threw a $20 cap in the trash.
     
  20. Feb 26, 2015
    47v6

    47v6 junk wrecker! Sponsor

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