Attached is a picture of my working Slough sender, different to the Paris one I believe. But it sounds as if you have isolated your fault. You can see the earth wire I put from the sender case to the body. It’s always awkward testing electricity near fuel tanks.
I am having fuel gauge problems at the moment as well, but it is my gauge that is at fault. I made one working gauge from two broken ones but the wires broke again when I tried to move the magnets to calibrate it (it would only work on the half to full sector). The wires are too thin for me to work on any more and all the gauge mending companies seem reluctant to work on it.
Good luck
Tony

