Tell me why ?

[mygmctruck1]

I went threw Heck trying to get my fuel gauge to read , tryed different gauge , new wire and I already had a new sending unit. When I oem out the sending unit it read per spec . I would hook up all the wires , had a good ground . I would lift the float arm and gauge wouldn’t work period.

Anyhow , took the truck in to fill gas tank to full and guess what the
gauge works !

How come I had to have a full tank of gas for it to start reading , when nothing else made it read before ? Never heard of such a thing !

Anybody else ?

[jimijam00]

Is that sending unit from China? Sometimes, its possible to get junk parts out of a new box.

[gmc684x4]

I am going to suggest it was most likely coated in oil that broke the circuit
once the new sending unit got washed in gas it washed the oil off the level sensor and started to give feedback to the gauge

The purpose of the oil is most likely a rust preventive measure

[mygmctruck1]

Originally Posted by gmc684x4

I am going to suggest it was most likely coated in oil that broke the circuit
once the new sending unit got washed in gas it washed the oil off the level sensor and started to give feedback to the gauge

The purpose of the oil is most likely a rust preventive measure

Plausible , but why wouldn’t It read at the gauge when I got at reading at the ohm meter ? That’s weird .

[gmc684x4]

As an electrician I have noticed great variances with meter readings
your meter has a better quality meter then the dash meter

Testing and repairing fire alarm using a Greenlee meter I read open on a long run spent lots of time looking for the issue went back and with my Fluke meter I got readings right away
re tried the Greenlee no continuity on the ckt as an example

I do have a new tank and sending unit in my shop for the last 10 years there both a bit oily to the touch

I do look forward to putting it in my 72 finally get it back on the road with a full sized gas tank