I've removed the gas sender unit to diagnose why the gas gauge doesn't work well. Even though tank is 3/4 full I only see about 1/4 of a tank on the gauge. I took apart the unit and used a multimeter and hoped to see a changing resistance out of the leads as I change the angle of the float. Is this how it's supposed to work?

So I'm thinking I have to adjust/bend the piece to get better contact with the track. Or maybe the track is worn too far. I already cleaned the track and leads with electrical cleaner. Anyone have any experience getting these things to work again?

Generally best to just buy a new sender. Mine had leaked and the float had gas in it, screwing up the readings.

The change in resistance takes place between one connection on the top of the sender and the metal mounting ring of the sender. The other connection on top of the sender is for the low fuel warning light. When the float is close to the bottom (empty) it closes a switch contact again to the mounting ring. The mounting ring must make a good ground to the fuel tank and the tank a good ground to the car for the gauge to work properly. I add a ground wire under one of the sender mounting nuts to a good ground in trunk. This sort of insures a good ground for the sender to operate properly.

spider2081 wrote:The change in resistance takes place between one connection on the top of the sender and the metal mounting ring of the sender. The other connection on top of the sender is for the low fuel warning light. When the float is close to the bottom (empty) it closes a switch contact again to the mounting ring. The mounting ring must make a good ground to the fuel tank and the tank a good ground to the car for the gauge to work properly. I add a ground wire under one of the sender mounting nuts to a good ground in trunk. This sort of insures a good ground for the sender to operate properly.

That's the info I needed. Thanks. The gauge did work last year so I'm thinking I disconnected the ground. I'll check that. Thanks.

I should have mentioned disconnecting the light blue/yellow wire at the sender, the gauge should read empty. Grounding the light/blue/yellow wire and the gauge should peg beyond full. So if your gauge reads 1/4 when you should show full maybe the tank or the sender to tank ground connection is poor. The ground is made through the mounting bolts.

I am assuming you know the float is not leaking as previously mentioned.

It works great now. I cleaned the bolts, sender unit metal cover and gas gauge works perfectly. Thanks for the info.

Also cleaned the battery cable connections and extra ground cable in the trunk.