Intermittent failure to start, fuel pressure craziness

Had a chronic rough start condition, found that with the key off fuel
pressure dropped to zero rapidly.  added an in-line check valve and ever
since have intermittent failure to start, even after replacing the whole pump.
wiring connector is supposedly o.k.  Now, hooked up a FP guage and left it
connected.  car starts, runs great, but park it for 2 to 30 minutes and it
won't start. found that pressure RISES when parked warm despite the key
and the FP relay being in my pocket. Guage only reads to 100 psi but
pressure is much higher.  loosening the connection at the test rail and
burping off some of the pressure allows the car to start easily.