1990 lumina3.1 Euro starts cold, runs ok until stop engine, then wont restart

This event just started occurring in the last 2 weeks. I can start the engine just fine when it is cold overnight or several hours cold. It will run seemingly fine until I get to where I want to be. When I go to restart it, if it has not been minimum 4 hours since running, it will crank nice and strong but no start. When I turn the key on hot or cold engine, I can hear the pump pressurize but I have not had the pressure tested yet. Only once did I get the service engine light but when I hooked up the sensor reader, I had no sensors showing bad. It flashed the good code only.

I have replaced the fuel pump relay and the fuse right next to relay. I do not know where to check next. If anyone has any suggestions on what to check and how to do so, I would surely appreciate it. Thank you

When the problem occurs, have a helper crank it, while you visually check for spark at the plugs. If you have spark everywhere, use a gage and check fuel pressure. Some of the national brand auto stores used to loan out a fuel pressure gage, if you don't have one. Also, use a noid lite and check for injector pulse. An intermittent rpm signal can drive you crazy?

To check for spark at the plugs, pull a spark plug wire loose, use a known good plug or spark tester in the boot. Ground metal part of plug/tester to metal part of engine, watch for spark, engine cranking.