Until you get to the sender, tank up and reset the trip meter to zero. When you get to 250 miles, tank up again and note the number of gallons needed. That should give you a good indication of number of miles before empty.

Most senders just get dirty and sticky. The sender is located on the driver's side under the carpeting behind the back seat, under an aluminum cover. There is a forbidding plastic screw, but I just used a pair of regular pliers (up side down) with the handles stuck between the fins at 180 degrees apart to loosen it and unscrew it.

The sender wire is plugged into the harness over by the fuel pump, unplug it and pull the sender straight up. Take it to your work bench.

The cylinder cover has 3 or 4 indents to hold it into place. Pry them back with a screwdriver or needle nose pliers and remove the cylinder. Note how the level gauge 'floats' over the wired coil and the wires spread apart as they go up.

Very gently, wash the wires in soapy water. Never wipe up and down the wires, just around. Rinse well and pat down with a towel and let dry.

Re-insert into car, with cylinder back in place of course. It should work just fine.

A lot of times, it is just oily residue from dirty gasoline that coats the inside of the sender.

Klaus
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Why are Volvos so endearing? Its just a car.