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Old 09-02-2019, 09:24 PM   #1
parb
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Join Date: Aug 2017
Location: mountain view, CA
Posts: 361
Fuel sender

Just checking in with those that have more experience that me.
My fuel gauge doesnt seem all that reliable. I bought a new fuel sending unit from brothers and installed it. My fuel gauge shows about 3/4 full when really full and when. Its at 1/4 left I can only get 10 gallons into the tank.

I assume it's a bad fuel sending unit? Or anything else I should check first?
I may just live with the issue for a while but wanted to check with the experienced folks first.

Its a bone stock 72 GMC Jimmy.
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Old 09-03-2019, 12:40 PM   #2
SeventyOne
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Join Date: Mar 2007
Location: Oakland, Ca
Posts: 1,382
Re: Fuel sender

I could be wrong but i think some sending units have the wrong ohms (newer trucks were different than 67-72s) so the gauge never reads right. Try searching "fuel sender ohm" for some fun reading.

This might be real helpful: https://67-72chevytrucks.com/vboard/...d.php?t=640615

I bought my sender from classicheartbeat - haven't used it yet, but i trust them more than brothers.

good luck!

Last edited by SeventyOne; 09-03-2019 at 12:41 PM. Reason: link
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Old 09-03-2019, 02:56 PM   #3
parb
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Join Date: Aug 2017
Location: mountain view, CA
Posts: 361
Re: Fuel sender

So i may have a 0-50ohm variable resistor in my fuel sender instead of a 0-90ohms resistor?

That would suck, but at least i know.

There is no one who has built a voltage to current mirror circuit to adjust the currents to similar levels as a 0-90ohm resistance circuit?
That seems like it would be relatively easy to do and its just a couple of transistors.

Its been 35 years since i last calculated an voltage following current mirror so if someone has a working circuit i would be happy to borrow it... anyone?

Last edited by parb; 09-03-2019 at 03:07 PM.
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