Fuel Tank Venting

Discussion in 'General IH Tech' started by sully0812, Jul 7, 2016.


  1. sully0812

    sully0812 High Wheeler

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    So I dropped the gas tank on my '77 today, to cure a leak from a rotten hose, and some fuel delivery issues that I suspect were related to a pinched hose. I discovered that of the six lines hooked up to the tank. (Aside from the filler and the overflow), the only one that was functional at all, was the fuel pickup. The remaining five lines were all cut off and capped with screws in them.

    And no... there is no longer a vapor separator in the panel in the back.

    So, because I like to keep things clean, I picked up five brass plugs, to remove the fittings from the tank (poly), and do away with the capped lines altogether. But then it occurred to me, that a tank vent may be important for purposes other than emissions. Such as accounting for expansion and contraction of fumes as temperatures change.

    So... is there any good reason not to proceed with my plan to simply cap the five fittings on the tank, and run with only the fill tube, the overflow tube, and the pickup? Or should I be concerned enough to try to plumb up a vent? And if I do, what is the simplest and most functional setup for that? (Is it really necessary to run lines up to the engine compartment, add a charcoal filter, and plumb it into the manifold?)
     
    Last edited: Jul 7, 2016
  2. sdhachey

    sdhachey Farmall Cub

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    Others may have better recommendations but I can tell you that the aux. fuel tank on my older IH pickup has just a fill tube, sending unit pickup, and overflow (back to the fill tube) that also serves as a vent during fill up. The other stuff you describe on your Scout was more for emissions purposes. So it seems like your simplified plan will work but let's see what other feedback you get. BTW, I tried to send you an email about a Scout II half cab that is available locally so let me know if you still need the info. Hope to catch up with you at the Dublin show.
     
  3. jtorre4272

    jtorre4272 High Wheeler

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    Just make sure you use a vented cap. All of the later ones were non vented as the venting took place at the charcoal canister.

    My '79 tank came with all the emissions equipment but I ordered a new poly tank without any of that and I simply have a sending unit line to the fuel pump and the filler neck with overflow attached.

    I prefer the pre-79 (?) filler necks. They do not have the trap door design like modern cars have and instead are a large opening the diameter of the tube that is able to freely vent fumes when filling up. But I am thinking you lose the ability to "lock" in the fuel station nozzle for hands free fill ups as a tradeoff.

    For some reason the '79 and later versions also have a steel overflow line all the way back to the base whereas the earlier versions used a rubber hose part of the way. In the process of restoring the '79 I robbed the filler tube from the '76 knowing about the potentials for poor venting at the charcoal canister.

    I did get a NOS canister and plan to run a line all the way to the tank when the time comes, but I will cap it off at the tank in a way that still makes it look like it is hooked up. Also plan on installing the separator baffle, but will not be hooking up to the tank either. All will be there for cosmetic reasons only.

    Joe T.
     
  4. MrKenmore

    MrKenmore Y-Block King

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    If you garage you Scout, you may want to consider installing the fuel vapor separator and charcoal canister. It can get smelly if it's in a closed environment. My Scout did not come with a separator at all. I wish it did. I doesn't hurt anything and keeps the gas fumes inside the fuel and venting system. My tank does not have the ports on each corner like you're describing.
     
  5. jtorre4272

    jtorre4272 High Wheeler

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    Geez, I thought everyone else shared my love affair with gasoline fumes? Figured it was a rite of passage for anyone who wrenches! That or a spray of fuel mixture to the face when adjusting the carb/timing for the first time and you get front fire. Safety glasses? Come on. When you are at that point where you fire her up for the first time after a major repair or rebuild and you can't find the glasses in your toolbox, you figure, "what can go wrong? I'll deal with it." We've all been there.
     
  6. tolly256

    tolly256 Farmall Cub

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    Fuel tank venting, should my filler neck have two connections? 76 Scout II and it only has one


    Sent from my iPad using Tapatalk
     
  7. jtorre4272

    jtorre4272 High Wheeler

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    The one from my '76 I recall also used a charcoal canister and an emissions tank. It was originally from California but I seem to recall charcoal canisters were in use very early on the scout II. Maybe the federal compliant versions didn't use them til later?

    Here's a picture of my filler after blasted and epoxy painted. One overflow connection that terminates to a rubber hose going into the top portion of the tank in same general area. image.jpeg
     
  8. tolly256

    tolly256 Farmall Cub

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    Thank you very much. I have been told there should be should be no open lines coming out of the tank for venting


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  9. jtorre4272

    jtorre4272 High Wheeler

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    your statement is correct as long as you replace the original non vented cap with a vented one. They are easy to find.
     

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