Oldsmobile/Buick Repair: 99 buick GS reagle 3.8lt supercharged, buick gs, voltage relay

Question
turn key on has 48psi fuel pressure car will start and fuel pressure drops until car dies. as soon as car dies fuel pump will renergize back to 48psi regulator good fuel pump new.ecm shows misfire because of lack of fuel????

Answer
Hi
I would say yes the misfires are probabally due to lack of fuel.
I would check current draw on the pump, see if it  is drawing around 4 amps. Does it go up or down? It MAY be loosing voltage.(relay poor contacts)
May have a bad ground circuit.
I would check pump electrical first.
Hope this helps
Good Luck
Pawl