1996 K1500 4.3L Vortec 76K miles

Truck will start and stay running for 5-10 seconds, then die

Fuel pressure (as measured at engine side of fuel filter) rails to 60PSI (only have 60PSI gauge) at key on, slowly drops as engine is running until the engine dies ~5-10 seconds later (fuel fressure at time of stall is normally 40-45PSI)

If I just key on and don't start truck, pressure will rail and quickly drop to ~10 PSI first ignition key-on or two. For all key-on cycles after the first couple, pressure will rail at key on and drop to ~55PSI and hold there for at least a minute.

I am suspecting it is either fuel pump of pressure regulator, not sure how to figure out which with common garage tools. Any suggestions?

Thanks

I have a 98 Silverado that was in a bad accident thats doing the exact same thing... Replaced the fuel pump and it works perfect now.. vortec engines require 60psi minimum to start and 55 to stay running.. I'd say you've got a bad pump, or a real bad filter :D