1941 Fuel guage sending unit

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pistonbroke

Well-known member
Hi all, I'm having a isue with my sending unit and I'm looking for knowlage. At first it worked fine but took longer and longer to register each time I turned the switch on. Now it dosn't move at all. If I ground the wire to the tank it pegs full instantly. I've pulled the unit, took 600 grit to the pionts and the little diode or whatever its called and then it works for about three hours of run time then faded away again. What is my problem? Tim
 
Appears the screws that attach the sender to the fuel tank are not grounding the sender...OR ...you may be missing a ground wire inside the sender by the contacts. Try taking a ground wire and touch it to the sending unit body, not the wire terminal.
 
Thank you all. So far Ive replaced the floatand ran a ground wire to a mounting screw on the unit with no luck so Im off to the archives Thanks again, Tim
 
Any good KS sending unit up to 56 can replace the one you have, the top part is the same for all those years. You just have to adjust by bending the arm to match the one on your current unit. I have a chart that gives the dimensions of how to set the good working or NOS unit. If you go to my MISC photo folder it is in there somewhere. If you can't find it Message me with your email address and I will send you a PDF of this chart that came in the box with a NOS unit. You may have noticed that there are tabs to control the stops for the arm travel up and down.
 
From deuce roadster's MISC photo folder...
picture.php
 
So let me clarify my reson for posting the original question. Ive been inside the sending unit twice and had it out three times. Getting it out is a royal pain. The tank is a poor\cheap reproduction which has the sending unit in the wrong place so I have to remove/lift the bed to access it. The tank can not be dropped out the bottom . (Note to self, you get what you pay for). The grounding was my first thought but changed nothing. Next I thought of the float and replaced it but it was not bad so now I have spare. Then I very carefully sanded the points with 600 grit. This worked but the reading on the guage got slower and slower then stopped all togather. The last try was to sand the pionts again and clean the mount for the diod . It did the same works great then slowly quits working . It still read correctly, it just to longer to get there until it just stopped working . Sorry to be so long winded but wanted to be clear,and a big thank you for all the good advise. Tim
 
If possible, please post a photo of the gas tank sending unit you are working with.
Is it an original King Sealy unit or an after market unit that claims to work? If it's not an original KS Unit it will never work with the OEM gas gauge since the KS units do not operate on the Ohms Law principle.
 
It's the orginal from my old tank plus I have had manyof these over the years and would know an aftermarket reostat type at first glance. It looks identical to the images posted above. Good thought though. Tim
 
No aftermarket reostat type sending unit will work accurately or at all with the stock KS gauge. That is because the KS system works on the FREQUENCY signal from the points in the sender and the gauge is designed to work off this FREQUENCY. Not Ohms resistance or Voltage. If you get a reostat type sending unit you will have to also buy a gauge that works on the principle of that sending unit be it Ohms or Volts.

IF you take a stock gauge out, you will see behind the face in a place you cannot see when installed, a single mark near the top at maybe 10 or 11 o'clock. To calibrate the gauge, you put 1.5 volts to the gauge and adjust the needle to that mark. This is the ONLY the only time you put volatage to the KS gauge.
 
Also I have 2 NOS gas tanks and when I installed one of them in my 46k mile 40 coupe, it was a WAR like removing the old one. I am convinced the tanks were installed before the body drop at the factory. It is not just aftermarket tanks that are difficult to install.
 
WOW! Deuce, I didn't know about that gauge mark and how to adjust the gauge. Is the same true for the 1940 fuel gauge?
 
19Fordy--I have some new gauges and will look. I personally have never had to adjust a fuel gauge. I just check on the bench with the sender and gauge being used to see what the needle does with the travel of the arm. There are 2 tabs that limit the travel of the float arm. If anyone can't read the chart that Pete posted, message me with your email address and I will send you a clearer copy. I read about this in a Ford Service manual.
Mike aka deuce_roadster
 
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