This can't be rocket science, yet I've screwed it up twice. I have the pickup unit from a 1977 chevy van welded into my stock tank. This gives me a removable unit that has all the extra things like return line, access to inlet sock, and 12v sender.

I have bought a 0-90 ohm guage twice, installed it, and both times, I get the full reading only. The tank is grounded, the pickup unit is grounded. I am getting some continuity between the sender wire and ground. Not much but it isn't open either. Could this be the source of my trouble? I grounded the sender using one of the vent tubes rather than the rusted out original location on the edge of the ring. Is this acceptable or is the ground supposed to be isolated from that part of the sender?