I have a 2000 Bonneville with the normally aspirated 3.8L engine.
The gas gage reads correctly from full to about 1/2 a tank (based on the mileage the car has always averaged), but when the tank gets under 1/2, the gage is totally untrustworthy. At about 1/4 tank (for example), it may read 1/4 tank, it may read 1/2 tank, it may read 3/4 tank...and will change as it's driven.

I am guessing this is due to the fuel sending unit. I'm also guessing that the sending unit is integral with the pump. So, if those guesses are correct, does that mean it's time for a new fuel pump?


Thanks!

Yes sounds like sending unit, there is a fix you might want to try
http://www.bonnevilleclub.com/forum/viewtopic.php?t=71718&highlight=sending

Thanks for that link - sounds like exactly what's going on. I'll post back with results after I install the part!