strange gas level readings

[Dan54669]

I have a 99 Buick Century that has started to give me goofy fuel readings. When I start the car it will normally read what I believe to be an accurate level of fuel. If the car sits idling for a short time it will read past empty. Sometimes it will read somewhere in between the two levels. I've heard a bad ground will do this. Others have believed it to be a bad sending unit ($260-ouch!!) Any ideas would be appreciated. Thx

[tri-power]

Best to check the ground's to see if you have bad contact before jumping into the sending unit. You are heading in the right direction.