Chevrolet: 2001 LS1 Camaro --> Hard starting fuel pressure drops instantly, fuel pressure gauge, walbro 255

Question
Ok, here's the deal.  My Camaro gives me a hard time starting whenever is sits for more then 15 min.  If I "Key" it two or three times to let the fuel pump build pressure it starts fine.  To check this out I put a fuel pressure gauge on the rail.  When key it to on the Fuel pressure jumps to 58psi, but as soon as the fuel pump stops it fails intantly to 0 psi.  If the car is running the fuel pressure sits at 58psi and it runs fine.  Once I turn it off if falls intantly to 0 psi.  Unless this car is different then other FI cars I have owned it should NOT fall that fast.  

Is this the pump? Injectors? regulator?

Thanks for any help.

If it is the fuel pump can I just replace the pump or do I have to do the whole hanger and such?

Answer
The check ball in the fuel pump is done. You just need to change out the fuel pump. Get a Walbro 255 LPH pump. You can replace the pump by dropping the exhaust and suspension or by cutting an access panel through the trunk area with a dremel which is what I did.