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| | | | Joined: Dec 2019 Posts: 37 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2019 Posts: 37 | Hello. I'm rebuilding a 47 3100 that I bought last year. When I got it the fuel gauge was showing about half full. I went ahead and filled t up and the gauge showed between 3\4 and full so I thought it was working but not exactly accurate. When I started taking it apart the gauge was showing a little less than half but when I pulled the tank off it was almost completely empty so something is wrong. The truck has been updated to 12 volts. It looks like it has the original gauge. The sending unit looks like it has been replaced. I put a meter on the sending unit and it goes from 0-30 ohms. What do you think my problem is? Thanks.
1947 3100
| | | | | Joined: Jan 2010 Posts: 4,263 Shop Shark | | Shop Shark Joined: Jan 2010 Posts: 4,263 | Is it a 6 volt gauge?
If so and you put 12 volts on it did you used a voltage reducer on the power post at gauge?
Check the search function, some have reported no issues using 12 volts on 6 volt gauge, others report fried gauge.
I wouldn't worry about it till your done rebuilding it. Then bench test before reassembling in truck | | | | | Joined: Jul 2000 Posts: 2,188 Insomniac | | Insomniac Joined: Jul 2000 Posts: 2,188 | You might have to bend the sender's float arm. Measure how far the float drop is and compare it to the depth of the tank.
Gord 🇨🇦
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1954 1/2 ton 235 4 speed
| | | | | Joined: Sep 2010 Posts: 2,306 'Bolter | | 'Bolter Joined: Sep 2010 Posts: 2,306 | My gauge was reading incorrect and it turned out to be the brass float had fluid in it making it sink and would read about half when the tank was full.I could not find a hole in the float but replaced it and worked correct , I think over the years condensation filled the float | | | | | Joined: Jan 2002 Posts: 2,839 'Bolter | | 'Bolter Joined: Jan 2002 Posts: 2,839 | You might have to bend the sender's float arm. Measure how far the float drop is and compare it to the depth of the tank. Yup! To me, having a accurate gauge when you are running low in fuel is very important. I would drain the tank, then add just 4 gallons (assuming your tank is 16 gallons), install the sending unit and then check to see how close to 1/4 tank reading you get. If off a little, tweak the sending unit's arm as Gord mentions. And yes, those floats can develop a leak or two.
Craig My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear My truck ....... Respect The Rust If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.
| | | | | Joined: Mar 2010 Posts: 10,272 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,272 | You can solve the leaky brass float issue with a plastic float for a early to mid 70s Jeep. They clip right on the wire just like the brass ones do.
I gave up on aftermarket brass replacements and when I buy an aftermarket sending unit, I switch out the brand new brass float for the plastic Jeep one. you can find them on Amazon and ebay.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
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