Fuel Bleeding Down in Fuel Rail Quickly

I have a 2002 Intrigue (3.5L) where the fuel pressure bleeds down to zero approximately 10 seconds after the ignition is turned off. I already replaced the fuel pressure regulator (it had fuel in the vent tube). It started perfectly for one week after FPR replacement, then problem returned. Once car starts, it runs perfectly, but it is very difficult to start if it has been sitting a while. My question is, what holds the fuel pressure in the fuel rail? Could the new fuel pressure regulator have gone bad after one week? Could a defective fuel pump allow fuel to bleed back into the gas tank and cause the fuel rail pressure to drop to zero? I no longer have fuel in the vent line of the FPR, but the pressure at the Shrader valve drops rapidly after the key is turned off. Any advice would be appreciated.

Leaking injector is a possibility here.

You could pull the fuel rail and check that the injectors arent leaking.

You could also pull the spark plugs and see if any of them are fouled from sitting in fuel from a leaking injector. Unless this has been occuring for a while, or occurs often though, they might not be fouled up bad.

I'm not sure about GM pumps, but most of the German cars with Bosch pumps I've worked on had a check valve at the fuel pump. I would assume GM may have something similar.

I'm not sure about GM pumps, but most of the German cars with Bosch pumps I've worked on had a check valve at the fuel pump. I would assume GM may have something similar.

I believe you are correct in assuming that. Thats another good reason to allow a couple seconds of having the key in the "ON" position to allow pressure to build up.