Hello, so I have the same issue with my 94' B250. It drives for about 2 hours then dies and starts back up some amount of time later. I had the computer replaced which fixed the issue for a while but then the same problem started happening again within 1000 miles. Something is causing my computer to keep going out and I don't want to keep replacing it. The problem seems heat related as when it is really hot outside the van dies faster than when it is cool outside. Could it be that expansion somewhere is causing a circuit to disconnect? Any other starting point suggestions?

 

Is it the PCM causing it now though? See what's missing next time it dies... Fuel, or spark, or both.

 

I had a similar issue and turned out to be a failing crankshaft position sensor.