Cranks, but no start in the Morning

I have a 2002 Chevy S-10, 4WD, 4.3L engine and occasionally it cranks, but will not start in the morning. I used a spark checker and showed good spark. So I put a fuel gage and found the fuel pressure went to 62 psi when I keyed the ignition on and the engine tried to start briefly, but I observed the fuel pressure starting to drop during cranking and the engine would not try to start. This engine has the poppet valve injectors inside the intake manifold and needs at least 55 psi to start. The fuel pressure hold good (62 psi) if I key on with no crank and may drop 10 psi in ten minutes. I also looked inside the throttle body when it would not start and could not smell any fuel. Once the engine does start it generally starts fine the rest of the day. Not sure how the PCM powers the fuel pump during cranking (crankshaft sensor?), Because the oil pressure sensor only provides a signal to the gauge according to the wiring diagram. No code are in the PCM, so could it be the fuel pump, fuel pressure regulator or cranshaft sensor?