86 S-10 4X4 2.8 Dies when cold & while Driving
 

This started after fuel pump was replaced months ago, but probably not related. Cold engine would start, but die, start but die multiple times. Replaced pressure regulator and that seemed to fix problem for a while. Next, engine would die while driving. Move trans. to neutral and would restart and drive fine. Now in a very intermittent time frame has issue on start and while driving. No codes. Any ideas? Thanks, Jim

Is this S10 a TBI injection?
Three things to check.

Ignition
Air
Fuel

I would re-check that fuel delivery. Also check the electrical part of it.
Look for repairs, flying wires, other inconsistencies towards the fuel pump and also in the engine bay towards ignition.
Fuel pressure check is highly recommended - from shared forum experience it is not enough to assume a new fuel pump is good.
When it dies and does not start, do you have spark?
Air is normally not a problem and mechanical. Usually you know when there is issues with that part.

Couple of things come to mind that I have personally experienced with a 2.5 TBI 2.5 in a 1989 s10 and a 1.8 TBI in an 80s Buick Firehawk if the normal things don't plan out.

On Firehawk the alternator would start overcharging (high voltage) and this would freak out the computer and cause it to shut down to protect itself. Then would start and immediately do the same thing again as soon as alternator started to charge again. Monitor voltage while the problem occurs.

Second one I never did figure out exactly where, but on the S10 5-6 times per year would die on the highway and refuse to start for 15 min to half an hour. Of course when I had tools it would always be fine. Replaced a lot of stuff trying to fix this. Only thing that finally fixed it was a complete engine wiring harness to computer from the junkyard. Apparently a bad connection or short somewhere. Or simply manipulating the wiring harness fixed it.

Of course an intermittently shorting injector or distributor can also cause the computer to shut down.

Note if the injector sprays and fire goes from the coil when cranking and not starting. This might help guide you.

And possibly do one at a time - fuel and spark outside the engine is kinda dangerous...

Yes, this is a TBI 2.8.

On the cold start issue, once it started it would run fine until shut off. Stops on errands after that no issues. I could live with problem if I had to, but the stops while driving are serious as I do not want to be stranded in some of the places I'm going. Will recheck from the fuel pump to the engine again. Thanks for your suggestions, guys!

Problem was resolved with new fuel pump
 

Even though the fuel pump had already been changed several months previous to this issue, it was found to be the culprit. No starting or dying while driving have occurred since the replacement.

Good you got that fixed.

We see a lot of these fuel pumps fail within very short time. Seems to be related to cheapo parts as most of the complaints are concerned with a cheap first replacement.