Very weird problem

I have a 90 SSE. After driving for about 10 minutes, the try and restart within a 5 minutes the engine just cranks and will not start. If I release the fuel presure from the rail it'll fire right back up. It drives normal with no issues while running. I replaced the fuel pump relay as it was the cheap way to start. I then check the pressures as instructed in the factory service manual and they are well within spec. If the car sits for 10-15 minutes it'll start without having to purge the fuel rail. Any thoughts would be greatly appreciated.
Doug

check for a restriction in the fuel return line or the evap canister. Try pulling the plugs and see if they are wet, it could be flooding if there is too much pressure or a vacuum leak. good luck. michael