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Can gas from main tank leak into saddle tank?

Discussion in '40- & 55-Series Tech' started by Gregor, Jul 19, 2005.

  1. Gregor

    Gregor

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    I thought my gas gauge was broken because the last 2 times I have put gas in it has shown it empty within a day or so. Meanwhile my saddle tank has been leaking after I fuel up. I know my saddle tank leaks in the top half so I don't put in over 11 gal. Is it possible that the gas in the main tank is going into the saddle tank & then leaking out?
    I should mention that my gas gauge only works on the main tank so I can't tell if the gas is actually going into the saddle tank.
     
  2. 65swb45

    65swb45 Supporting Vendor

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    Guess it would help to know year and model, plumbing etc. Hypothically, if your tanks were set up like mine, where rear tank is designed to plumb into front, and your front pressurized [expanded] from heat creating a positive head pressure, and your delivery line from the rear tank was into the delivery tank of the front [vs the vent tube] it could create enough pressure to run backwards.

    Simple test: leave the filler cap on the front tank loose when you park it and see if it still siphons off the gas when the tank has no pressure.
     
  3. Gregor

    Gregor

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    Thanks for the reply. My rig is a 77 FJ40. The main tank has always built a lot of pressure since I've owned it. It got to the point where fumes were leaking thru the seam in the front of the tank. I pulled the tank a couple of years ago & sealed the front seam. Since then I never put the gas cap on that tank. The saddle tank is not plumbed into the main tank.
     
  4. dgangle

    dgangle total rice SILVER Star

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    What in the hell is a saddle tank? I thought those were on class 8 trucks. Do you mean a rear auxilary tank?
     
  5. camcruiser13

    camcruiser13

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    ditto
     
  6. Gregor

    Gregor

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    Sorry jargon police - I mean rear auxillary tank
     
  7. brian

    brian SILVER Star

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    not really a good way to get good answers....new guy......

    you have problems if gas is getting from one tank to the other, and you say they are NOT plumbed together. so they both have a supply line running to the FP/carb? what about return lines?
     
  8. camcruiser13

    camcruiser13

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    thnx for having our back brain. new guy fix the hole in the "saddle bag" then what if you fill your "saddle bag" up all the way then fill your regular tank and see if it leaks? it wont leak into the "saddle" if its full will it? :cheers:
     
  9. Plowboy

    Plowboy

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    do you have a control valve to switch from one tank to the other? If you do, the vavle may be letting fuel syphon from the main tank back to the aux. The main tank being above the aux causes the problem. That was happening to me. Replace the three way switch and the problem stopped.
     
  10. dgangle

    dgangle total rice SILVER Star

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    I have a similar problem with my 14 gallon poly tank transfering its contents down the 4 barrels of my Quadrajet/350. The only leak I am aware of is into the carb. He, he he.

    Brian, Ditto. BTW, I work for a company in Lebanon. PM me and we'll talk.
    Camcruiser13, Ditto, ditto.