1999 Chevy S-10 Fuel Pressure drops afer priming

I have a 1999 GM S-10 with the 2.2L MFI fuel injection. It does not start right away but turns over several time before it starts. I checked the fuel pressure and found the when the ignition key is turned to auxillary position the fuel pump runs the prime cycle and the fuel pressure goes up to 55psi but when the pump prime cycle stops the fuel pressure drop back to zero almost immediately. When the engine is started the fuel pressure with the engine idling the fuel pressure is 35 psi and then when the vacuum line is pulled off the fuel pressure regulator the pressure goes up to 42 psi. When the vacuum line is replaced the pressure returns to 35 psi. Is there something wrong with the fuel pump or a check valve on the fuel pump that would require it to be replaced. Is this something that can be lived with?

Thanks.