GM-GMC: 1994 4.3 v6 silverado stalls, fuel pump relay, aldl connector

Question
"After driving home from work about 20 miles I exited off the expressway when I came to a stop The engine stalled like someone turned off the fuel. It took about 3 times of 20 cranks before it started I thought it might have been because I had run low on fuel in the red warning area the day before. It ran fine the rest of the way home, approximately 7 miles. I drove it that night back and forth from the grocery store with no problems.The next day I went to the local bakery, about 7 miles, and when I returned,as I was turning into my driveway the same thing that occured the day before happned again. I checked for codes on my code scanner. Code 12 comes up "nothing wrong" I checked the fuel pump by jumpering + side 12 volts to the ALDL connector [fuel pump ck] and listened for the fuel pump. It ran when I touched the port on the ALDL connector, next I checked the fuel pump relay and its fine. I replaced the oil pressur switch, just in case. Nothing indicated the MAP sensor so I dident replace it. The only thing I dident do is check for fuel pump pressure. Every time I tried to start the truck dureng these test and after it started. The next morning I went to work, and it happned again just before I got to work ..about 20 miles. I cranked it 20 times, turned the ignition off for a few seconds, cranked again 20 times. It started but shut off right away..so I sat for a few seconds with the ignition off. I tried to start it again and it eventually started. Keep in mind that this seems to happen only after the engine has been at operating temperature          Any help would be appreciated."

Answer
You accomplished a lot of good, rational, troubleshooting.

It could be also be an ignition problem.  The ignitor (or module) in the distributor may be failing as operating temperature.  It may or may not set a code when it goes on "vacation" and it might be hard to identify as the culprit.  If it is the electronics at fault, it will get worse as the weather gets warmer over the next few months.

You might also have partially clogged the fuel filter with debris from the bottom of the fuel tank.  You might try changing it.