OK, this could be confusing to describe... i'm thinking fuel pump or relay maybe even regulator... you tell me...

i pull rail and injectors up out of intake...
i put pressure gauge on...
i put a cap under the injector to catch fuel...
i turn key to run...
pump primes to 40 psi...
i try to star and while trying to turn over the engine the pressure slowly bleeds down...
the second i turn the key from start to run the pump primes and the pressure rises to 40...
try to start again and the pressure drops...
i look for fuel in cap and there is NO fuel in cap...
i suspect a leak so i look for a leak and i DO NOT find a leak...

what could this be?