Still having problems with my gas gauge

First of all these are all brand new parts from Classic Parts. This is on my 51 GMC, 12 volt, negative ground. Before I got started, I could turn on the key and the gauge would go to 1/4. I added gas and no change.

I tested the ohms on the sending unit with it out of the tank - it doesn't work. I opened it up and can see the windings have broken connection. I ordered a new one. Hopefully that will solve that problem.

I decided to check the gauge. I grounded the sending unit wire, at the tank, to a good ground. Nothing - stayed at 1/4. Now, I pulled the gauge from the dash which ungrounded the gauge. It went do "E". I touch the sending unit wire, at the tank, to a ground and it goes to 1/4. Is the gauge supposed to be grounded in the housing? My problem before was that I got nothing at all out of the gauge so I sanded the inside of the housing so the gauge made contact and the gauge jumped so I thought I was good. Not so.

I know there are a million threads on gas gauges. I must have looked at them all. I'm stumped and really disappointed in these parts. Any help?

 

Bench test the sender with an ohm meter. As you move the float arm, the ohms should change. Be sure your meter is in range. If that operates ad it should, connect to Guage wiring with jumpers and the needle should move.

 

The gauge dash unit needs a ground from somewhere; either through the mounting bolts or if it has a seperate grounding connector.

If you have that grounded for sure, and then ground out the sender wire, it should go past full. If not, I'd say the dash gauge is bad too.

 

polarity at the gauge is important, make sure you put power to the correct side so as not to damage the gauge.

 

Your truck was positive ground when 6v ... you have to reverse the wires when going neg ground. Past experience on a '54 GMC (completely different gauges) was that reversing current causes a rapid failure, at least with the 3 I've burnt up.

 

before you put the sending unit in the tank, hook everything up and move the float arm up and down and notice how your gauge reacts.

 

Thanks guys. The gauge is a Chevy gauge. I'm going to order a new gauge too. It sounds like this one is bad too. I did connect the wires backwards once and it immediately blew a fuse so maybe I messed it up.