How does my engine get fuel?
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How does my engine get fuel?

  1. #1
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    Default How does my engine get fuel?

    So I'm about to replace the sending units in this heap that I bought when I notice that both tanks have welded bungs on the top side rear of the tank. Then I realize that I don't know a damn thing about sending units and how the fuel gets out of the tank. This boat is set up with a mechanical fuel pump. Anyone care to hold my hand and walk me thru this? All my previous junk has had gravity feed/electric pumps.....never jacked with a sending unit 'til now...

    Respectfully;

    Jamie W.

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    Senior Member lbhsbz's Avatar
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    USCG approved tanks use a draw tube that installs in the top of the tank. The tube is either permanently installed or its part of the fitting that screws into the bung. In the fitting, you'll also find an anti-siphon valve....which requires a certain level of vacuum from the pump to open and allow fuel to be drawn through it. Most of us have gotten rid of the anti siphon valves because they suck and are unnecessary.
    GN7: "If you were to have ever had two brain cells you could rub together and make heat, you be dangerous"

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    Quote Originally Posted by lbhsbz View Post
    USCG approved tanks use a draw tube that installs in the top of the tank. The tube is either permanently installed or its part of the fitting that screws into the bung. In the fitting, you'll also find an anti-siphon valve....which requires a certain level of vacuum from the pump to open and allow fuel to be drawn through it. Most of us have gotten rid of the anti siphon valves because they suck and are unnecessary.
    Excellent tutorial, thank you.

    So the pick ups in my tank are essential there to chat with the fuel gauge? Can I run a small diameter siphon hose down the tube to purge the tanks of old gas?

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    Senior Member holorinhal's Avatar
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    If you have a square type tank, look on to of the tank and there should be a round alum play with 4 to 6 screws and a couple of electrical connectors . That is the sending unit. You will take out the screws and the whole unit, with arm and float will come out. Just replace with new. Be carefully of sticking any thing thru the pick up tube, as there is usually a screen on the bottom end.

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    Senior Member lbhsbz's Avatar
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    To get the old fuel out, go pick up a fuel line/pump ball kit for an outboard...makes siphoning easy after you get rid of the anti-siphon valves
    GN7: "If you were to have ever had two brain cells you could rub together and make heat, you be dangerous"

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    Senior Member wpmxwb's Avatar
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    Sorry to thread jack. But how long has uscg required the fuel tanks to have the pickup on top? I have tanks with a uscg sticker dated 1979 and the fuel pickup is on the bottom.

  9. #7
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    Don't touch anything until you have disconnected the battery!



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    Senior Member sandeggo's Avatar
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    I like the jiggler siphon hoses. It has a marble in the crimped metal end. Jiggle it back and forth a couple times and its siphoning. You can get em at lowes for like $5. Don't get the harbor freight one.
    The pick up tubes are different than your sending units more than likely.
    Last edited by sandeggo; 10-20-2012 at 06:15 AM.

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    Senior Member SBS933's Avatar
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    Default Call in an expert

    Call my son, he can empty those tanks in a heartbeat. He never has a problem sucking mine dry as soon as i park it after a trip.

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