Been following this thread as I was replacing a leaky tank on the car I recently got. The gauge has also been reading wrong when I got it.
Guess what, set up the new tank, plugged in the wires and the gauge says full. Unplug the gauge wire (green/black) at the sender and it reads empty, so same symptoms as Dycecooper.
Moving the arm up and down has no effect but the low fuel light seems to work correctly. Tried a spare sender and also a new one with the same result. I already have the carpets out and the wires look good all the way as far as I can tell so I guess its the gauge?
I need to get the axle back in next so I can at least move rhe car then I'll have a look at the pesky gauge.
Russ
1980 TR7 Sprint DHC
Dursley
UK
http://tr7russ.blogspot.co.uk/