Fuel Gauge not registering correct level

[akidd737]

I have a 1988 Buick Regal. My fuel gauge does not show the correct fuel level. It reads at full level most of the time. Then at times it drops to diffrent levels then goes back all the way up. Sometimes it stays at full all the time. Ive been told it might be the fuel sending unit or the fuel gauge. How can I diagnose these to find out which one is the faulty part? Can somebody please help me? Ive already run out of gas once and I dont want it to happen again. Thanks in advance.

[bearcat5]

There are three ways to check this out. First, jack the rear of the car up. Find the harness going to the gas tank. See if the harness is pluged together anywhere along it lenght. If so unplug it. It should be a two wire harness one goes to the gauge and one is hot. If you know someone with a known good sending unit you can attach the unit to the wires and move the floot up and down while someone is watching the gauge. Move the floot slow and make sure the ing is in the eng run poss. If the gauge reads correctly its the sending unit. If not, it's the gauge. Your secon option is (can you solder?) to cut the wires going to the tank repeat the above instuctioins and solder the wires together when finished.
You may hear that you can run straight voltage to the gauge but that realy does not tell you if the gauge is bad. Just that it moves.
Your final option is to bring it to a mec. If you never droped a gas tank before and are not mec. inclined it is not an easy job on your back. You have to have a second person to help you.
Good luck.

[akidd737]

Thanks alot for the advice. Its exactly what I was looking for. I will try it. Im sure it will work.

[regalfriend]

I had a similar problem with one of my older cars...at this point it may be easier to keep count of your milage

[regalfriend]

I had a similar problem with one of my older cars...at this point it may be easier to keep count of your milage