'92 LT1 with cycling fuel pressure

[calirebel]

When I turn the key on I hear the fuel pump start up but within about 2 seconds I hear a pressure pulsation in the fuel lines under the hood, sounds
like the pump is cycling on and off.
The Service Engine light flashes on and off with the pulsation. Car will start but runs
with erratic idle and stalls. Fuel rail pressure pulsates between 42 and 46psi and when engine stalls it bleeds down to 30 psi in about 60 minutes.
Pressure regulator is new. So is the fuel pump relay.
Any ideas on how to test the pump while it is still in the tank? Or possible issues that can cause this with the Service Engine light flashing.....
Thanks....

 

[GWinter]

have you checked if you have constant 12 volts to the fuel pump? If so I would suspect the fuel pump. The service light may be from erratic reading from some sensor because of the fuel supply changing. This is just a logic thought.

you could unhook the pump and jumper it and see if fuel pressure stay steady