fuel tank sender and gauge

[80spiddy]

Trying to diagnose a new tank and sender gauge reading. It doesn't appear to read accurately or move much. Before I installed it, the sender showed full travel on the gauge reading when moved by hand and empty light went on when sender arm down. Now, with installed, the tank is probably 3/4 full and gauge reads 1/2. Remove electrical wire to sender and gauge reads empty. Ground sender wire and gauge reads full. Pull other electrical wire and no empty light. I tried grounding the area around sender, but no help. What should I be looking for?

[spider2081]

I think the gray/red wire is the light wire. it needs to be grounded for the light to light. I don't think the fuel gauges are accurate through out the range from empty to full. They should read full when the tank is full and empty when the tank is empty. Where the light lights is somewhere around 2 gallons in my car.

[80spiddy]

The car ran out of gas in garage with gauge reading 1/2. I pulled sender and it worked as it should. The problem was , the float was catching on the side of the tank and wedging itself stuck. Tank filled would push float up, but wouldn't fall as gas was used. I had to bend the metal rod some for clearance. All is good. Finally!

[spider2081]

Interesting, I wonder if the sender had a manufacturing defect.