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Thread: Gas pump cutting out at a little over 3/4 tank

  1. #1
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    Gas pump cutting out at a little over 3/4 tank

    When I fill up at the gas station now, the auto shutoff triggers at a little over 3/4 of a tank. Anyone have some insight as to why this might suddenly be happening?

  2. #2
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    You probably have already tried setting the pump handle to the slowest fill-rate. My first guess is that your gauge is off. I'm not sure how to physically tell if your tank is full. I suppose you could make a dipstick.

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    Fuel sender issues

  4. #4
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    Run a couple of bottles of fuel system cleaner through the tank, to clean the resistance card in the sender.
    https://www.bimmerforums.com/forum/s...6#post30070776
    Last edited by Vintage42; 11-22-2018 at 04:16 PM.
    BMW MOA 696, BMW CCA 1405

  5. #5
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    All give the fule system cleaner a try... I was wondering if it was moisture in the tank or something but the guage being wrong makes more sense, thanks.

  6. #6
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    Can you fool the auto shut off by readjusting the nozzle so it’s either deeper in or not as far in? Sometimes the way you have it in there can affect the auto shutoff

  7. #7
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    Quote Originally Posted by Ring Rat View Post
    ... the auto shutoff triggers at a little over 3/4 of a tank...
    Quote Originally Posted by Wrench Turner View Post
    Can you fool the auto shut off by readjusting the nozzle so it’s either deeper in or not as far in?...
    I think he means the tank fills up but registers 3/4 on the gauge.
    BMW MOA 696, BMW CCA 1405

  8. #8
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    On a related note, it's interesting to do an internet search to discover how a gas pump nozzle stops. For my entire life, I understood it to be caused by back pressure, mostly due to my dad telling me that. It's not. It's caused by liquid gas being sucked into a little hole underneath the spout. That causes an imbalance of pressure from a venturi that moves a diaphragm which closes the valve.

    I never knew that hole was there under the spout and now I understand why the nozzle would not trip off when filling a gas can, but would trip when filling a tank.

  9. #9
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    Ran a few fuel system cleaners through it over the past month and nothing has changed. If I fill it from when the low fuel light comes on, it takes around 10 Gal, and as mentioned the gauge only registers 3/4 tank. Is there possibly some vent in the filler neck thats blocked? Or is a faulty sending unit likely to read 3/4 tank at full tank, and read empty when there is 1/4 tank left?

  10. #10
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    When my light has just come on, and I fill it up, allowing the automatic shut off, it often takes around 10 -11 gal (same as you). My guage says "full". I don't think I"ve ever put in more than 12, and that's after about 15 miles with the light on. (I just looked, and our cars hold 13.5 gal in the tank, so that means my car would have about 2.5 gal still in it when the light comes on. That would be a safe 40 miles, which seems about right.) ... So ... my theory again: your guage is wrong. ... I always reset the trip odometer, so I can monitor mileage with every fill-up. You can use it to check the gas guage.
    Last edited by zellamay; 01-07-2019 at 08:29 PM.

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