Anyone else have fuel pour out the vent tube!!???

Fuel and Air Systems

  1. koosh

    koosh Well-Known Member

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    Installed a new fuel sender about a month ago, went pretty well, but never really filled the tank to the top....decided to take long cruise today, so last night filled gas tank to the top, about mile away from my house. Drive home, no issues....(was expecting a leak from the sender gasket with my luck).
    This morning, pulled out of garage and parked on front lawn for pictures... front yard has slight downhill grade so car facing downward very slightly....
    All of sudden gas leaking onto lawn dripping from differential! After panicking, crawled under car to check that sender seal expecting to be wet with gas BUT WAS DRY....there are 2 vent tubes, 1 goes up into the trunk, the other about 4" tall, and curves back toward the ground----gas coming out. Level ground, no issues! Anybody else experience this? Should be simple fix with a longer/higher tube?
     
  2. aeon280

    aeon280 FBBO Gold Member FBBO Gold Member

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    Stuck float. My dual hollleys have that same problem because being a project the car doesn't get driven. You can try shutting it off and taping the bowl with a screw driver. Usually works for me.
     
  3. Fran Blacker

    Fran Blacker FBBO Gold Member FBBO Gold Member

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    There are 2 rubber elbows I'd check those. There's a rubber grommet where vent tube goes into tank. Mine weeps if I top off tank. Did you use your old lock ring when you did sending unit? The old ones work best, if you got a thin one. Could the fuel run on the lip of tank to driver side and fool you that its from the vent?
     
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    • Cranky

      Cranky Moderator Staff Member FBBO Gold Member

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      How many miles was the station from your house and was the weather very warm after filling up? Had a 70 Challenger that would do that after a fill up if I topped it off on a warm day......
       
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      • koosh

        koosh Well-Known Member

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        Um, I'm talking about at the gas tank?
         
      • koosh

        koosh Well-Known Member

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        Not sure about elbows, will have crawl back under and check...
        I used original ring, but like I mentioned, no leak from the sender area....or any wetness on tank itself....when I saw gas hitting back of the differential, the only thing that could reach that is the short vent tube....figured I would just make it higher?
         
      • koosh

        koosh Well-Known Member

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        1 mile from my house, but it did not leak the day I filled up, only this morning when car was parked slightly dowhill.....
         
      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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        When you did the sender did you remove the tank? Those elbows get hard as concrete, you need to cut lose if they're like that. You can bend/wreck the vent tube that goes into the tank. When a junkyand they had a 66 Charger, same tank. Told them be careful not to wreck the vent tube. They bent they s!*t out and were pissed when I told them I didn't want it.
         
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        • koosh

          koosh Well-Known Member

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          I removed the tank.....both vent tubes I removed by loosening the hose clamps...I have both vent tubes coming out of short hoses with clamps.....its a new tank. So the short vent tube (which LOOKS like steel brake line), from the hose, goes upward about 3-4" then hooks back downward, I just figured since the tank got filled then I parked on a decline, it was seeping out the short tube. Gonna grab a piece of brake line and just go higher before curving it back down?
           
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          • Fran Blacker

            Fran Blacker FBBO Gold Member FBBO Gold Member

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            Its been awhile since I messed around with that small line. Is it possible that it rusted out down low? Have a fill tube in my garage if I find it? I'll have a look. Gas tank.JPG
             
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            • koosh

              koosh Well-Known Member

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              That's not my configuration, mine is like this:
              Note the 2 vent tubes, long one goes up into trunk, next to it is the short "suspect"
              IMG_7780.JPG
               
            • Fran Blacker

              Fran Blacker FBBO Gold Member FBBO Gold Member

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              Duh! Dumb I should have looked at your avatar. Had it in my you had a 66. This happens to often, not so much here but to often.
               
            • koosh

              koosh Well-Known Member

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              Lol! No worries, you've been big help!
               
            • chtampa

              chtampa FBBO Gold Member FBBO Gold Member

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              Some of the repop tanks had the tubes switched inside the tank.
               
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              • steve340

                steve340 Well-Known Member

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                I am wondering if modern fuels gas off more than the fuel used when that tank vent system was designed. Therefore building up more pressure in the tank that the vents have to deal with. Or was the design pretty shitty to begin with and owners either did not notice or care that fuel puked out. Maybe someone can chip in on that thought.
                I just spent the last few days playing around with my 1968 GTX with exactly the same issue. I would drive only a few miles and it would puke out and the garage would often smell like a filling station. When then fuel gases off which it does just sitting in a container or a fuel tank it builds up pressure in the tank and this pressure will just push fuel up out most any vent.
                The original design is not what you would call bullet proof.
                With the fuel filler on a B body being so low the cap is not vented so you rely on the tank vents to allow air in so the fuel pump does not implode the tank and to allow any pressure build up out.
                This pressure pushing out is what your car and mine was suffering from.
                I modified the vents on my car and it looks like it has worked. However I have only been on one fairly decent run so I am confident but not 100% sure problem is solved.
                I hate fuel leaks as I am paranoid about some dick with a stray cigarette torching my car.
                By the way I extended the both vents to up in to the trunk under the parcel tray and it still managed to push fuel up that high. I was blown away how high that shit went up.
                 
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                • Cojohnso1

                  Cojohnso1 Well-Known Member

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                  My '69 does this from time to time. It seems when car has ran for some distance with full tank. If tank goes to 3/4 or less? It doesn't leak. leaking only appears after car shutoff? Taking gas cap off stops the leak. It too from the short tube. And on rear diff. I haven’t figured it out. But just haven't Been filling full for now. I have also seen this complaints of later 60s model Bs. I believe it's only to tanks with behind license plate filler tubes?

                  This happens with both 93 octane 10% ethanol. Or 91 octane non-oxy. But I haven't ruled out what steve340 asked? Is today's fuels producing higher vapor pressures?
                   
                  Last edited: Jul 13, 2019
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                  • koosh

                    koosh Well-Known Member

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                    Wow.....so me making the "shortie" a tad longer/higher won't do it?
                     
                  • koosh

                    koosh Well-Known Member

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                    So I ended up driving it for about an hour out and an hour back yesterday after siphoning out about 5 gallons yesterday.....after getting home into garage last night I saw no leaks.....now has about 1/2 tank, woke up this morning to gas fumes in the garage....panicking, I looked all over under the car and saw no leaks! Still venting??
                     
                  • koosh

                    koosh Well-Known Member

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                    Can we not just install a vented gas cap?
                     
                  • chtampa

                    chtampa FBBO Gold Member FBBO Gold Member

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                    Reverse the rubber vent hoses.
                     
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