Filter / Regulator check valve?

Hello!

I used the EVFS07848BK-AMZ1 kit for the LS in my 2005 Canyon, with the factory GM fuel pump in the tank.

Is the fuel filter / regulator supposed to have a check valve in it?

When my pump shuts off after prime, the rail pressure IMMEDIATLY drops back to 0 PSI (within a second). I have no external leaks, and the truck runs great; I have no reason to suspect a fitting, line or injector problem.

Please advise! Thank you!