I have a 94 Camaro 28 where the pump primes but then loses pressure when you crank and it won't start. I have pulled the fuel lines and fuel comes out when priming but not when cranking. Have replaced the pump 3 times and the fuel pump relay. What would cause this I'm stumped.

 

What pressure does it prime to when the pump shuts off?

How fast does the pressure drop?

Does the gauge actually indicate "0" when you turn the key to "start"?

Have you scanned it for codes? DTC 16 for the optical cam position sensor does not turn on the SES light, but it does shut down the fuel system, including pump and injectors.