I am trying to figure out what is wrong with my fuel gauge. If I remove the ground for the fuel sender, what should the gauge do? Go to extreme full or empty?

It is hard to tell with out knowing how it is wired in the dash. When I replaced my tank and sending unit I hooked mine up before I installed it to make sure it worked. Good thing I did that because the first one they sent me was defective! It wouldn't even work and when I looked at it I could see the reistat (sp) was broken. They sent me a new one no questions asked. When the new one arrived I hooked it up to watch it work. I would move the float by hand and watch the needle in the guage go up and down. When I unhooked the ground wire my guage would go way past full.

ditto. When I removed my ground wire, the guage pegged past full.

If the sender is unplugged, the gauge should swing past full. With the hot wire to the sender grounded, the gauge should go to E or below E. The element should measure somewhere around 180 or 200 ohms with a full tank and very low, perhaps 5 ohms or less with an empty tank. The sender should vary resistance with fuel level, but it is not exactly a linear rate.

Unplug the wiring harness if you want to measure the sender unit and measure from the sender hot to ground. My car has a jack for disconnecting the sender inside the trunk. Harbor Freight has a great digital meter for this sort of testing on sale for less than $5.

If you measure an open circuit across the sending unit when it is unplugged from the wiring harness, the sender has a broken connection. It is common for the wiper to wear through the wirewound resistance element. It's also common for there to be a faulty ground connection.

You can also substitute a potentiometer from Radio Shack for the sender to check out the gauge action. Look for one around 200 ohms or buy a few different fixed resistors between 5 and 200 ohms to try out.

If your gauge works for part of it's range but not all of the range, the wire wound resistance element is damaged in the middle of it's range.

Lastly, the dash relies on chassis grounds too, so check them as well.

Ninety ohms is full, 0 ohms is empty.

This should help..

Fuel Gauge Diagnosis... (http://www.chevelles.com/techref/ftecref18.html)

Dan,

Thanks for the link! I had seen that article in the past, but when I needed it I could not find it. Well it turned out to be the sender. the fuel line was separating from the top plate and the top plate is where the ground wire is attached. A quick trip to Firewheel Classics and the problem was solved. Still a pain to drop the tank though....

Ground wire, I thought, is supposed to be attached to the pass side tank strap foundation.

One end of the ground is attached to the fuel sender top plate and the other is attached to the body right above the tank. The sender side grounds through the fuel line which is attached to the sender resister. The spot solder joint between the fuel line and the top plate had cracked on mine, which interupted the path from the sender to ground.