Trying to get the last non-functioning gauge working again. 71 CJ5 w/Dauntless V6. When I got it the PO had replaced the original rear fuel tank and skid plate with a home made tank made from steel plate. I originally had purchased a replacement fuel sender, but the one I pulled out of the tank did not look anything like the replacement I purchased. I measured the resistance of the unit I pulled out, and it did not change as I moved the arm. I then purchased a universal VDO sending unit. Before installing in the tank I hooked up the fuel gauge wire and ground wire to the terminals and manually moved the float. The gauge responded as intended, so it appeared the new sender would solve the problem. I bolted the new sender in place, reattached the fuel gauge and ground wires, and hung the tank. After filling up the tank, the fuel gauge still shows empty. I notice a slight movement when I turn the ignition on, but nowhere like it was when I moved the arm outside of the tank. Anyone have an idea why the sender would work outside the tank, but not when it was inside? Grounding should not be an issue, as the sender has a ground terminal on it which I used to successfully test it outside of the tank. It almost seems like the gas in the tank is not moving the arm up at all.