The fuel gauge on my 1990 240 sedan, automatic, stopped registering and the needle stays at the bottom. Other functions on the same fuse such as turn signals work so it is not the fuse. Where should i start looking for a wiring fault and what should I look for?

Thanks.

The first place I'd suspect is the feedthrough at the sender on top of the fuel tank. Rust lifts the protective insulator from the sender's mounting plate and allows moisture to corrode the wiring until it is gone.

To verify, use a test light (with an incandescent bulb) to probe the gray wire at the sender harness. Shown below is a 245, but your sedan is even easier to reach this connector. It is under a plastic cover held in place with snap-in fasteners.

If you get light here, the gauge will respond a little, and you've verified your need to go in the tank to solve the problem. If unsure, ground this gray wire and you'll see the gauge peg at full.



In The Tank
--
Art Benstein near Baltimore

Captcha, Captcha go away, come again some other day.

Have a look in your trunk. Lift the carpet and find the wiring harnesses that go through the metal plate in the left side of the trunk floor, up in the raised forward section of floor.

One wiring harness is for your speedometer pickup on the differential. The other harness is for the functions related to the fuel sending unit: Power to the in-tank pump, ground, and the fuel gauge sending unit.

Check the plugs to make sure everything's secure and clean. Remove the plate (not sure in 1990 if it's phillips head screws or Torx). It's glued down with some sealer as well if it's never been opened.

Below the plate (you'll want a flashlight) you can see the top of the fuel tank. There's a round ring holding down a flat plate with a bunch of steel tubes and a wiring harness coming through it. It will be all rusty and probably have sand and grit on it as well, but when it was new it looked like this:

http://www.fcpeuro.com/products/volvo-fuel-tank-sending-unit-kit-240-260-1367253kit

Inspect the condition of all your wiring up to the top of the tank, and report back with any findings.

Good luck!
--Rob