Stumped

Re-test:

Ground disconnected lead at tank from fuel gage to a good ground, gage should read full with key in run position.

With feed from gas gage disconnected recheck ohms between sending unit’s electrical terminal, and good ground. You should get a reading proportional to the chart Zigs provided:

The values are:

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

Reconnect sending wire to sending unit, and the steel bridging ground strap that jumps the rubber between sending unit and fuel line. Sometimes these straps lose their electrical connection to ground, and need their connections cleaned to once again conduct. The sending unit has to be grounded well to work, if the connection to ground is poor, or nonexistent because of corrosion, the gage will not read correctly because of the increased resistance introduced to the circuit.

Picture what an additional 50 ohms from a bad ground would do the above chart; a full tank would read as empty. (10 Ohms + 50 Ohms = 60 ohms).

If gage still does not read to known level of fuel in tank after remaking ground, the problem is with the sending unit.