1940 Ford fuel gauge issue

[Ggmac]

I now use a modern voltage drop . Good thing I had a coffee can full of gauges , you can hardly find a 80s car in the junk yard .

[Automotive Stud]

Alright so I decided to revisit the stock sending unit. I popped the cap off and looked at the links that 19fordy posted. I see the points and everything appears to be in decent shape, although a little crusty. I noticed before removing the points plate that regardless of the float position the points are contacting each other, they move up and down as a unit. From some of the linked posts that seems correct. My points aren't stuck together. I'm going to try to clean this up, maybe take a point file to the points, and try the adjustment procedure outlined with the star wheel and see if that gives me any satisfaction. When I first got this car on the road the fuel gauge worked for the first tank until the float sunk. I replaced the float on this sending unit but was never able to get it working right again.

[Anteek29]

Bet cleaning the points will get you going again.

[19Fordy]

Be gentle with the sending unit. Do not damage that "carbon resistor" but make sure it's fully contacted. Make sure you float has no hairline cracks. Run a ground wire from the sender to the frame to make sure you have a good ground.

[51woodie]

Auto Stud. Be careful poking around in the sender, as others have cautioned. When I was repairing mine, I somehow lost the little insulating button that is at the end of the copper arm where it rides on the adjustment cam. When it is missing, the sender shorts to ground. It took me a bit to figure out what was wrong, but the pictures I took on disassembly showed the button missing. I had to make a new one out of plastic on the lathe. As well, I used 1000 grit wet paper to clean the contacts. One more tip, disconnect the power to the coil when testing the fuel gauge, or you might/will fry your ignition.

The adjustment "cam" need very little movement to make a difference in the gauge reading.

[47Monarch]

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I got a sender from Joe's Antique auto instructions stated good for 6 or 12 volts. Works ok stays on full for long time when it gets to 1/4 hope I have comfortable walking shoes. I think I messed up cutting the float rod

[19Fordy]

You can easily solder the float rod to make it longer.

[JayChicago]

Originally Posted by 47Monarch

I got a sender from Joe's Antique auto instructions stated good for 6 or 12 volts. Works ok stays on full for long time when it gets to 1/4 hope I have comfortable walking shoes. I think I messed up cutting the float rod

You didn’t necessarily mess up the float rod. That’s how the aftermarket senders act. They will work on our gages, but with no accuracy.

You can add a resister to the wire going to the sender to bring the gauge needle down some. Try about a 7 or 10 ohm resistor. It is trial an error to get it close to accurate when empty. Still won’t be accurate when tank full, but that’s not a problem.