67-72 Chevy Truck fuel gauge diagnostics 101

[TBONE1964]

Originally Posted by jjzepplin

Allrigty. Went out and tested the sender today to find it is reading 90 ohms-hmm. Went inside the cab and pull the sender wire and it reads 90 ohms- hmm. Pulled what I thought was the ground clip for the gauges and nothing happened to the gauge.
Is there more than one ground clip?
This gauge and sender tested fine out of the tank. Why would it be any different inside the tank?
The only difference I can find is the tank sender ground was a jumper wire.
I have a ground wire on the tank that previously was not hooked up but it is now.
Sound like a ground issue?

JJ,

The tank is full? If you are reading 90 ohms testing the sender, that would tell me the tank is full and the float is up all the way. If you were reading 22.5 ohms, then I would say the float is stuck at 1/4 tank or the sender is not working correctly

The little ground clip for the cluster is just an extra ground as a back up. The ground for the cluster is in the connector I believe with out looking it up is in the number 7 location. It is a black wire.

If you have a ground issue at the cluster, the temp gauge and/or lights would not work correctly. They all share a common ground.

What will happen now if you hook your jumper ground back up? Try it and see what happens. Are you still reading 1/4 tank? That would indicate to me that your ground is good. If you pull ground, the gauge should roll over to 3 o clock.

Keep us posted and have a good holiday,
Tom