It's not hard to pull the sender unit and check it. Lift the cover in the trunk, disconnect the lines (make sure you mark which is the feed, and which is the return). I plugged the lines temporarily with a short rod to stop any return fuel. Disconnect the harness and remove the unit. You need to jiggle it a bit to get it out. You can clean the 'piano wires' with alcohol. I then filled a canister and checked the float still did its job. I think mine had gone to the bottom and somehow got snagged on the piano wires. Its been working again for 12 months now. Remember - you will be working with an open fuel/gas tank. Take every precuation you can think of, including being in a well ventilated area without kids, pets or mates that smoke.
John 535is 1989