Just wondering, how many volts should the fuel pump be getting? From what I've read, I imagine there may be a wiring problem between the relay and pump (as someone already said). I had this happen on an older car and one day the car stalled while driving. I could hear that the pump wasn't priming. It took a while to find it but I found that mice had partially chewed through the wires near the fuel pump and the pump wasn't getting enough power. Replaced the wires and the car started and ran better than it did for weeks. Damn mice! Kill em all!
Also, theone2043, you have to start diagnosing more thoroughly before ordering parts. I'm no Sherlock Holmes, but you are gonna end up replacing the whole car before this is over.
Seriously though, good luck.
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'08 Grand Prix base - '06 Montana SV6 - '76 L-82 Corvette