The ground wire from the sender to the guage housing was for bench testing. In the truck the ground would be made through the truck itself. Is the cab grounded to the frame?
If the wiring is correct the problem lies in the guage or the sender. Are they original or new? I got a new guage from Chevs of the '40s and used my old sender. If you are using your original sender, it should read 0-30 ohms. Check it with a meter to see if that is where the problem is.
It is frustrating to run into snags like this, but satisfying to find and fix the problem!]
Craig
