How to remove gummy buildup from old gas tank?

Discussion in 'Inboards' started by nopeda, May 22, 2019.

  1. nopeda
    Joined: Aug 2013
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    Location: GA

    nopeda Junior Member

    I have a 1968 Lazy Days Sportsman. 43 ft. long 12 ft. wide aluminum hull houseboat. One of the gas tanks hasn't been used in a long time, possibly 10 years or more. I'm pumping out the old gas which is very dark reddish in color with an electric fuel pump that seems to be having a hard time and is going very slowly...sometimes not pumping at all. I have the end of the intake gas line tie wrapped to a copper rod which holds it about 1/2" above the bottom of the tank, going in from the fill cap which is conveniently directly above the tank. With the copper rod I can feel a bunch of gummy build up on the bottom of the tank and when I pull the rod out there is a wad of what looks like tar stuck to it. The tank very unfortunately feels like it is welded in place or I would try taking it to a radiator place or something or maybe replace it entirely, but as I mentioned if feels welded in place. It looks like it's made of galvanized steel and a magnet sticks to it very well so it's not aluminum or stainless, right? Is there some fluid I can pour in the tank that will break down the tarry buildup so I can suck it out with the electric fuel pump? Something that will clean out the tank without hurting it and also clean the fuel pump without hurting it either?

    Thank you for any suggestions!

  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . . .

    Fortunately, I've never had to deal with this problem.
    I would think stirring the gasoline around would break up the lump(s).
    Brake fluid may be an option but it could destroy the pump...
    Can you suction capture the lump(s) and lift them/it out?
  3. Barry
    Joined: Mar 2002
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    Barry Senior Member

    I am hoping that your electric fuel pump is spark protected and is approved for GASOLINE< many fuel transfer pumps are for diesel only.
    If 12 volt, watch for sparks when hooking it up
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Use some E-85
  5. Rumars
    Joined: Mar 2013
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    Location: Germany

    Rumars Senior Member

    If the tank does not have an inspection plate you are in trouble. Acetone, laquer and paint thinners, carb cleaner, etc. will all break down the gums. Getting the soup out is another thing, it will clog the pump and depending on what you use may attack rubber and plastics. The fumes are highly explosive, no sparks permitted. Try to find out how it's mounted and take it out for cleaning.
  6. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Yes, one must be scrupulously careful to avoid anything that could produce a spark, or you could meet God earlier than expected.
  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

  8. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    sticksludge.jpg pumpsuck.jpg Put in some E10 gasoline, if you can cycle it with a pump would be good, as in the new gas it sucks out put it back into tank at other end, maybe your vent line is at other end of tank.
    The gums will be in the bottom of the tank, and the ethanol and new gas will clean it out.
    You can also pour in a gallon of xylene into the gas.

    You need enough to cover the entire tank bottom, if tank is angled, will take some more.

    5 gallon in my 150 saddle tank would not be enough, 10 gallons would do it.

    The stuff you get out, maybe you can evaporate in several large plastic mortar pans.
    They are black and wide open and can hold a lot of liquids.

    But do that in your own yard, cause it will take a few days.
    Plasgad Black Large Concrete Mixing Tub-887102C - The Home Depot

    My twin 1970 tanks loosened up decades of muck by the switchover to E10 gas.
    After it dries, the residue was like mud and water soluble.

    I sucked out mine using a vacuum pump, a large pickle jar. Created enough suction to clear out that nasty stuff.

  9. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    I made up a nozzle for an air line and jetted high pressure air from my compressor to loosen gunk in a fuel tank. That would help mix in any cleaner/solvent you add, and you won’t end up increasing the amount of liquid you’ll need to dispose of.
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