i own a 1984 cutlass supreme and i have a problem with my gas gage. i just recently replaced the sending unit and my gage is still incorrect. iIf i pu $30 worth of gas in it the gage will rise to the correct spot then 30 sec later it wil go to empty... What is the problem? and how do i solve it?

 

Is this the same problem it was exhibiting before? Could be a pinched wire between the gauge and the sender.

 

$30 ain't much gas these days, was the car running for those 30 sec's?
Sorry, couldn't resist.

 

I've found it's usually a ground, somewhere in the rear - clean, and replace the bolt and washer, too.

 

I've had 3 olds Cutlasses and none of them has ever had a working gas gauge. I keep telling myself I'm going to take the time to fix that. Maybe third times a charm.

 

Not sure about that. If it was a bad ground it wouldn't register the right amount at the start. Sounds more like a bad circuit board - cold solder joint - overheated on the front of the car. Shrinks back when no current, then overheats and drops the voltage. ??? Saw this on some 80's cars, especially with dash lights.

 

I think that era cutlass used a cheezy ribbon type connector for the dash gauges/wiring. I would guess it is a bad connection.

 

If you want to test the gauge, find the wire at the rear tail light harness going to the sender. On the older cars, its usually tan. I'd bet its the same color on the 80's cars. It will naturally go to the top of the tank

Find the connector and pull it apart. The gas gauge should go past full in a smooth fashion. Now take the wire on the harness side thats going back to the gauge and ground it. It should go smoothly to empty.

Chances are you have a dead spot in the rheostat on the sender. Full should read about 90 ohms onthe wire to the sender, empty should read zero. So if you have approx 1/2 tank, you should have 45 ohms from the sender. So for example, if its got 1/2 a tank and its reading zero ohms on your digital volt/ ohm meter, its a bad sender