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Featured Technical Sending unit problem

Discussion in 'The Hokey Ass Message Board' started by HOTRODPRIMER, Nov 6, 2018.

  1. I have replaced the gas tank in my '50 Ford coupe with a new one from shoebox central, I also replaced the sending unit and it still reads full with only 3 gallons of gas.

    The unit has been removed and check to see if the arm is set currently, reinstalled and still reads full.

    What the heck am I doing wrong? HRP
     
  2. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 2,602

    KoolKat-57
    Member
    from Dublin, OH

    Have you spoken to the folks at shoebox central?
    KK
     
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  3. LAROKE
    Joined: Sep 5, 2007
    Posts: 1,207

    LAROKE
    Member

    I'm thinking ground wire.
     
  4. RMONTY
    Joined: Jan 7, 2016
    Posts: 1,137

    RMONTY
    Member

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  5. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 4,093

    Bandit Billy
    ALLIANCE MEMBER

    HRP, fi you turn on the key and remove the signal lead on the sender the gauge should read full, ground it and it should read empty. This is the first step toward diagnosing that problem.
     
  6. upspirate
    Joined: Apr 15, 2012
    Posts: 1,696

    upspirate
    Member

    Is the sender the correct one for the gauge?
     
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  7. squirrel
    Joined: Sep 23, 2004
    Posts: 40,284

    squirrel
    Member

    that works on Chevys, but Fords work the opposite way.

    An Ohm meter, and knowing how to use it, will be very helpful in figuring out what's wrong. Do you have one? we can give you step by step instructions.
     
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  8. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 4,093

    Bandit Billy
    ALLIANCE MEMBER

    That explains why my ford gets such great gas mileage.
     
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  9. oj
    Joined: Jul 27, 2008
    Posts: 5,789

    oj
    ALLIANCE MEMBER

    Hate sending units and the whole tank/gauge circuit. having said that, Ford uses a gizmo attached to the gauge and it limits the voltage/current at the sending unit. What i do is disconnect the sending wire at the tank, then I connect a potentiometer in place of the sending unit then go thru the range - Ford used a lot of 76 (Full) to 6 (Empty) ohm circuits, use the potentiometer to go from 76 down to 6 and see if the gauge reads correct; if it does then read the sending unit - I suspect it will be a different scale. If it isn't and it reads proper range (with a volt/ohm/meter then you'll need to replace that gizmo I spoke of, there is an adjustable 'trim pot' available on Amazon that I use where you can set your 'Full' and 'Empty'. I hope it is just a mismatch between sending unit and gauge, thats the easy fix but if it isn't shoot me a PM and I'll link you to that trim pot.
    Did I mention I hate gas gauges? hatefilled things.
     
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  10. Has the car been converted to 12 volts? Is the sending unit for 6 or 12 volts? I'm assuming that the gauge and sending unit are voltage sensitive, aren't they?
     
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  11. To me, sounds like the lead from Dash gauge to the tank is grounded out before it gets to the Sender. Easy check, remove the wire from sender and turn on the Key. If it still goes to full disconnect it at the dash gauge turn the key on again. If it don't read anything then you know what's next.
    The Wizzard
     
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  12. squirrel
    Joined: Sep 23, 2004
    Posts: 40,284

    squirrel
    Member

    the sender is not voltage sensitive, but the gauge probably is.
     
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  13. F&J
    Joined: Apr 5, 2007
    Posts: 12,472

    F&J
    ALLIANCE MEMBER

    I have seen two types of repro senders for a 50 Ford car. One was pure cheezy/crappy looking and actually fell apart before it went in all the way. The next one the guy bought, looked like a very well made part and worked fine....(it was a stock 6v car though)

    .
     
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  14. I came to the conclusion that you are correct, the sending unit I used was from Summit and I believe it was 0-90 Ohm and I need a 73- 10 Ohm. HRP
     
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  15. Dennis D
    Joined: May 2, 2009
    Posts: 475

    Dennis D
    Member

    Can ya just paint the E and F on the glass different? :D D
     
  16. upspirate
    Joined: Apr 15, 2012
    Posts: 1,696

    upspirate
    Member

    :D:D:D:D:p:)
     
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  17. Slopok
    Joined: Jan 30, 2012
    Posts: 1,941

    Slopok
    Member

    E stands for enough!;)
     
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  18. 26hotrod
    Joined: Nov 28, 2009
    Posts: 683

    26hotrod
    Member
    from landis n c

    Electrical stuff mystifies me...…………….
     
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  19. corncobcoupe
    Joined: May 26, 2001
    Posts: 4,228

    corncobcoupe
    SUPER MODERATOR
    Staff Member

    Buy something done next time.:rolleyes:
    Look at the post count you would save !
    Geesh…..

    Bwhaaaa :p
     
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  20. Instant gratification, what would be the fun in that? if everything was easy we would never learn anything. HRP
     
    Last edited: Nov 6, 2018
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  21. 19Fordy
    Joined: May 17, 2003
    Posts: 5,802

    19Fordy
    Member

    The stock King Sealy 6V Ford dash fuel gauge will work only with the stock King Sealy Ford 6V sending unit as they operate on a heated bi-metallic principle, not the Ohms principle. If you change one or the other to 12V you need to get a matching corresponding unit as they both operate on Ohms principle. I have found that the easiest way to solve this problem is to use the stock OEM Ford fuel gauge and adapt the OEM Ford sending unit to the tank screw holes.
    To do this, both the fuel gauge and the sending unit must remain 6V. This has been discussed at length on Fordbarn. Here's a good start.
    https://www.fordbarn.com/forum/showthread.php?t=247544&highlight=fuel+tank+sending+unit
     
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  22. squirrel
    Joined: Sep 23, 2004
    Posts: 40,284

    squirrel
    Member

    I did that to the Edsel, I put a chevy tank in it because it was cheap and it fit. The sender works opposite. It never was a problem.

    fuel.jpg
     
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  23. Classic fix Jim! :D HRP
     
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  24. gasmanm01
    Joined: Nov 24, 2009
    Posts: 554

    gasmanm01
    Member

    Make sure you have good ground to the frame. Also you can test it out of the tank with a ohm meter. 10-140 is the range for empty to full


    Sent from my iPhone using H.A.M.B.
     
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  25. 41rodderz
    Joined: Sep 27, 2010
    Posts: 894

    41rodderz
    Member
    from Oregon

    I hate it when they read empty.:D
     
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  26. Dennis D
    Joined: May 2, 2009
    Posts: 475

    Dennis D
    Member

    Great minds............D
     
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  27. nochop
    Joined: Nov 13, 2005
    Posts: 591

    nochop
    Member
    from norcal

    Dynamo label maker, the best
     
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  28. squirrel
    Joined: Sep 23, 2004
    Posts: 40,284

    squirrel
    Member

  29. EVERYTHING electrical operates on the 'Ohms Principle', which by the way is called Ohms Law. You'll have different electromechanical means of utilizing the voltage/current involved, but the same laws apply to all circuits.
     
  30. Got the new sending unit in today and tested it before installation, it's wrong also :mad:

    So I did what I should have done previously and called Classic Instruments and talked to their Tech advisor and he assured me I needed the universal sending unit,240 Olms full - 33 Olms empty.

    Hopefully the third time is the charm. :rolleyes: HRP
     

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