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Old 11-03-2020, 02:55 PM   #1
Automotive Stud
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Default 1940 Ford fuel gauge issue

I'm having issues with the fuel gauge not reading correctly on my '40. It's converted to 12v, but it has a Mustang style voltage reducer feeding the fuel gauge. If I ground the sending unit wire it reads full, so I thought the sender had failed. I bought a reproduction Vintique 6v sender since I'm still using the original gauge, but on a full tank it still only reads about half full. Any ideas on what's going on here?
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Old 11-03-2020, 03:08 PM   #2
JSeery
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Default Re: 1940 Ford fuel gauge issue

I would try and go back to the original sending unit if possible, the resistance unit will be difficult to get to work (they can be made to work after a fashion, but not easy). Grounding the sending unit wire should give you a full reading on the gauge, so that seems to be working ok. Might try grounding one of the sending unit mounting bolts to a know good ground.

What the original sending unit is doing is opening and closing a set of point that is related to the amount of pressure applied by float. So if the extra ground doesn't help, check and see if the float is working correctly. If that is not the issue, you may need to open it up and see if the points need cleaned.
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Old 11-03-2020, 03:10 PM   #3
hotrodart
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Default Re: 1940 Ford fuel gauge issue

I have a similar issue on my '40 coupe......stock gauge/resistor with aftermarket sender. I am told the aftermarket senders operate on a different principle and cannot ever be accurate. Best bet is to find an original sender, or fix the one you have.
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Old 11-03-2020, 03:20 PM   #4
19Fordy
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Default Re: 1940 Ford fuel gauge issue

Wouldn't it be nice if someone would make a stock looking 12V 40 Ford fuel gauge to operate with the aftermarket 12V repro. sending units?
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Old 11-03-2020, 03:22 PM   #5
Hal Beatty
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Default Re: 1940 Ford fuel gauge issue

Or reproduction K-S sending units...
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Old 11-03-2020, 03:53 PM   #6
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Default Re: 1940 Ford fuel gauge issue

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This is the sender I used, thinking it would be fine with the stock gauge.
https://www.vintagepartsclub.com/for...ket-1935-1948/

What's involved in getting to the contacts in the stock sender? I already replaced the float because it was sunk, but it still didn't read properly so I bought this. Maybe I should revisit fixing the original.
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Old 11-03-2020, 04:05 PM   #7
deuce_roadster
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Default Re: 1940 Ford fuel gauge issue

All the KS 6v sending units are the same up to I think 56 or whenever they went to 12 v. The rod the float goes on is different for different tanks. There are also stops you bend to adjust the travel of the float arm. Most of those sending units can be cleaned up and work fine. I have a FOMOCO kit that is a replacement that has a chart which shows how to adjust the arm for different models and I can send a copy of the chart to you if you PM me your email address.
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Old 11-03-2020, 04:08 PM   #8
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Default Re: 1940 Ford fuel gauge issue

I was able to fix an oil pressure sender for a King-Seely gauge. It involved cleaning it up and dressing the points. It worked fine afterwards. The hard part was getting it apart, as they were designed not to be repairable. I got it apart and back together satisfactorily, but it looked pretty ugly when I was done. Since you can't see the gas gauge sending unit, looks are not so important.

There was also a "star wheel" adjustment on the oil sender.
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Old 11-03-2020, 05:07 PM   #9
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Default Re: 1940 Ford fuel gauge issue

I don't think we know that his first sender is an original King-Seely. That sender could be another aftermarket resistance unit installed by a previous owner, which explains inaccurate gauge readings in the first instance.

Last edited by JayChicago; 11-03-2020 at 05:14 PM.
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Old 11-03-2020, 07:50 PM   #10
19Fordy
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Default Re: 1940 Ford fuel gauge issue

This may help.
https://www.fordbarn.com/forum/showt...k+sending+unit

and
https://www.fordbarn.com/forum/showt...ng+unit&page=2
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Old 11-04-2020, 11:33 PM   #11
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Default Re: 1940 Ford fuel gauge issue

I used a stock fuel gauge, Ron Francis voltage reducer (VR-1 12-6V) and a sender from Yogis street rod parts 73-10 ohm. E was empty, F was full. In between who cares
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Old 11-05-2020, 12:53 AM   #12
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Default Re: 1940 Ford fuel gauge issue

Quote:
Originally Posted by fordor41 View Post
I used a stock fuel gauge, Ron Francis voltage reducer (VR-1 12-6V) and a sender from Yogis street rod parts 73-10 ohm. E was empty, F was full. In between who cares
Great if you can get it to work, a lot of people have trouble getting the resistance units to work correctly.
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Old 11-05-2020, 07:30 PM   #13
Charles Brock
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Default Re: 1940 Ford fuel gauge issue

I’m running 12 volts in a’40 with original gas gauge with a Ron Francis VR-1 reducer and a Bob Drake sending unit. The original gauge reads perfectly.
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