1990 Buick Regal Custom 3.1L shuts off after 5 min. warmup (won't restart until cold)

[redheadedtwizzler]

My 1990 Buick Regal Custom with a 3.1 liter automatic will start up at the slightest turn of the ignition key and runs terrific at high idle while it warms up for a full five minutes. But during the last minute of warmup, as the motor slowly calms down to almost a somewhat normal sounding idle, it simply shuts itself off as if someone turned the key off! After that, it refuses to start no matter how hard I try. I can crank the starter from now till domesday, but the engine cranks over and sounds as if it were completely out of gas, with not so much as even a single cylinder firing off. I've replaced all 6 spark plugs and the ignition control module (ICM) located under the 3 coil packs. What a pain that was to replace. But the problem still exists and I can't drive the car. All wiring and connecters under the hood appear to be in great shape. This is bizarre! I really wish cars were made as simple as they were back in the 60's and 70's. So many cars today are junked simply because of a bad sensor that nobody can figure out. I'm about to replace the brain box but first I need to know where it is located. Can someone help me with this or have any ideas that I've overlooked? Thanks

[maxwedge]

Welcome to AF, basics here, when it won't start do you have spark and fuel pressure?

[redheadedtwizzler]

How do I check for spark and fuel pressure?

[maxwedge]

You need a fuel pressure gage attached to the fuel rail port and a spark tester between the plug and wire. Due respect here, but it sounds like you may need some help with this.