So, I have searched through the forums and google to try and figure out this problem. No luck as yet. I just got this 05 Grand Prix (I believe it's a base or GT...not sure) with the 3.8L. When I got the car, the owner said the fuel pump was bad. I tested for pressure and yep, no pressure. The fuel gauge was reading just below 1/4 tank so I believed he was right. I ordered a new pump assembly...a complete unit with a new sender with it. When I went to pull the old pump out, I found the tank to be totally empty...with the gauge reading just below 1/4. I went ahead and installed the new pump assembly thinking ok, the sender is bad. Nope!! New sender, new pump and same problem....the gauge reads 1/4 tank off from where it should read. Any ideas on a fix for this? Thanks!