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- - Gas Gauge/sending unit issues… (https://67-72chevytrucks.com/vboard/showthread.php?t=842815)

inkslingrrr

03-08-2023 10:36 PM

Gas Gauge/sending unit issues…

OK, so back to you gurus for some assistance.
I replaced the gas tank in my ‘71 c10 from the behind the seat version to the bed rails kind from LMC. Now with a full tank, the (stock) gauge reads just under half. Tested the sending unit seems to work OK, pulled it out tested it by hand, Can still only get it to read just under half. Where do I start. Should I believe this is the resistors on the old gauge?
Once I learn to post pictures I’ll get some on here

Palf70Step

03-08-2023 10:40 PM

Re: Gas Gauge/sending unit issues…

Check for a good ground to the sending unit. That will mess with the gauge.

inkslingrrr

03-08-2023 10:46 PM

Re: Gas Gauge/sending unit issues…

Quote:

Originally Posted by Palf70Step (Post 9185071)

Check for a good ground to the sending unit. That will mess with the gauge.

Sending unit ground is good

pjmoreland

03-08-2023 11:21 PM

Re: Gas Gauge/sending unit issues…

Is the new sender a 0-90 Ohm type? The sender resistance should be around 0 Ohms at empty and 90 Ohms at full.

Did the gauge work correctly with your original sender?

inkslingrrr

03-08-2023 11:42 PM

Re: Gas Gauge/sending unit issues…

Quote:

Originally Posted by pjmoreland (Post 9185093)

Is the new sender a 0-90 Ohm type? The sender resistance should be around 0 Ohms at empty and 90 Ohms at full.

Did the gauge work correctly with your original sender?

Yes it sure did

RustyPile

03-09-2023 12:23 AM

Re: Gas Gauge/sending unit issues…

Quote:

Originally Posted by inkslingrrr (Post 9185067)

If the circuit is wired correctly and the grounds are good, it sounds like you have the wrong sending unit. With a full tank, a 30 ohm sending unit will read just under 1/2 tank when connected to a 90 ohm gauge.

pjmoreland

03-09-2023 12:32 AM

Re: Gas Gauge/sending unit issues…

Quote:

Originally Posted by inkslingrrr (Post 9185102)

Yes it sure did

That sure points at the new sender as the problem then.

If you have a multimeter, it would be good to measure the resistance of the sender to see if it has a 0-90 Ohm range.

inkslingrrr

03-09-2023 12:57 AM

Re: Gas Gauge/sending unit issues…

Quote:

Originally Posted by RustyPile (Post 9185119)

So nowhere in LMC catalog do I see a order # for a 90 ohm sender****

pjmoreland

03-09-2023 02:23 AM

Re: Gas Gauge/sending unit issues…

A stock fuel gauge is designed to work with a 90-ohm sender. See post #3 of the following thread for an explanation of how to test the resistance of your LMC sending unit.

https://67-72chevytrucks.com/vboard/...d.php?t=640615

inkslingrrr

03-09-2023 11:51 AM

Re: Gas Gauge/sending unit issues…

Quote:

Originally Posted by pjmoreland (Post 9185152)

So yeah, this is test it out as a 0 to 35 ohm sending unit… Now to find the right one or use a fuel bridge, need to thank everybody for their assistance because this is a little bit too techie for this old man!! thanks again

RustyPile

03-09-2023 08:48 PM

Re: Gas Gauge/sending unit issues…

Quote:

Originally Posted by inkslingrrr (Post 9185228)

So yeah, this is test it out as a 0 to 35 ohm sending unit… Now to find the right one or use a fuel bridge, need to thank everybody for their assistance because this is a little bit too techie for this old man!! thanks again

What's a fuel bridge?? [EDIT] Never mind, I found the answer...

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