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Thread: Mysterious fuel gauge level indication….. anyone run into this?

  1. #21
    Senior Member Haasman's Avatar
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    Removed the fuel sending unit. I moved the unit up and down and yes, the internal float does catch, right about mid-way.

    Should I take the sending unit apart and see what's causing the float to stick and see if I can affect a repair?
    Haasman

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  2. #22
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    why not? they are pretty simple internally.
    looking for 1972 911t motor XR584, S/N 6121622

  3. #23
    Jeff you stated this was a new sending unit, any chance that the aluminum tube was dented in any way? Do0esn't take much to stick the float. The usual culprit is that the float moves but doesn't give correct readings due to corrosion on the contact wires, shouldn't be the case here. Then there is heavy corrosion on the guide post that really sticks the float itself. Go ahead and take it apart, what have you got to lose. You'll need a 5.5mm wrench for the nut (after you bend back the lock tab.) Carefully pull the tube off the top plate. You'll see hair thin guide wires that make contact with brass contacts on either side of the float. See if the float slides freely with the aluminum tube off. If so, look for that dent I mentioned.
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  4. #24
    Senior Member Haasman's Avatar
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    Thanks Ed. Will do and report back.
    Haasman

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  5. #25
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    I have a 73.5 T totally stock and I had this same problem, but now it works perfectly. First I rebuilt the sender - crud on the wires, but gauge would still hang at 1/2. Bought replacement sender same problem. Then I cleaned all the contacts on the back of the gauges. Then I did what Ed suggested removing the new sender from tank while still connected and turning it upside down (after draining for a minute), and sure enough the gauge worked perfectly. I read a post somewhere about the gauge pressing against part of the tank and kinking the tube as a reason for making it hang, so when I tightened it I tightened the rear screws a little more than the front screws thinking maybe that would angle it a little from the rear vertical surface. I remember looking down the sender hole and seeing a rear vertical surface and wondering if it was possible that the gauge was pressing on it - can't say that I was convinced that is was close enough to matter. Ed has me thinking that there is no way that was that close, so must have been dirty contacts? It works perfectly now, with reserve light coming on with about 2.5 gallons. If you find a steep downhill it's a good way to see if the gauge will read lower than where it really should be.
    Last edited by Chickenstrips; 04-15-2021 at 04:30 AM.
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  6. #26
    Senior Member Haasman's Avatar
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    Chickenstrips- Interesting you suggest the bend .... later today will take a closer look at the tube, its mounting flange, the little wires and see if anything is obvious.
    Haasman

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  7. #27
    Senior Member Haasman's Avatar
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    I used a straight edge and could see a very slight bend in the tube.

    I then removed the sending unit and took off the lock washer and nut. Immediately the float was freer. Easily slides up and down in the sending unit tube. Was the nut/lock washer on too tight?

    I noticed corrosion at the top of the tube.
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    Haasman

    Registry #2489
    R Gruppe #722
    65 911 #302580
    70 914-6 #9140431874
    73 911s #9113300709

  8. #28
    Don't know how you have corrosion on a brand new sending unit? Since it freed the float by loosening the nut try slowly tightening and constantly checking float movement until you find that happy spot. The nut is lock tabbed so it won't loosen and fall off in the tank. Probably means the tube isn't perfect. Usually new senders come well protected in a stiff shipping tube.
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  9. #29
    Senior Member Haasman's Avatar
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    It is not new. I replaced the original several years ago with this one.... because ironically it was doing the same thing.

    Not sure why there is corrosion under the cap?

    I tried removing the plastic bottom but it seemed very reluctant to come out. Any tips on how to remove it? Or does the tube and plastic come off exposing the float and wires?

    I'd like to check the float and wires.
    Haasman

    Registry #2489
    R Gruppe #722
    65 911 #302580
    70 914-6 #9140431874
    73 911s #9113300709

  10. #30
    pull the aluminum tube from the top mounting plate. Notice there is a locating tab when reinstalling
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