I've been doing some troubleshooting on my Explorer recently. It suffers
from the hard to start problem as many others do. Sure enough, I found that
the fuel rail pressure bleeds to zero almost instantaneously after it's shut
off. The other interesting thing is that the fuel pressure reads 64PSI at
all times when running, with or without the vacuum line to the FPR hooked
up.

So, it sounds like my FPR is stuck closed (causing the pressure to go to
64PSI) AND the fuel pump is faulty allowing the pressure to bleed back into
the tank through the supply line. Has anyone ran into this problem and it
only be the FPR? It seems unlikely. It doesn't seem possible that the
fault lies solely in the fuel pump.

My next step is to:
1. Double check the fuel pressure with another gauge.
2. Double check the idle fuel pressure spec. The Haynes could be wrong.
3. Replace the FPR and see what happens.
4. Replace the fuel pump if (3) doesn't fix it.
5. If that doesn't work, give up.

On a side note, the truck never really runs poorly from a drivability
standpoint, just hard to start, and intermittently down on power. Hopefully
there isn't some other issue.

Any help is appreciated.