'96 Silverado 6.5L stalling

My buddy has a '96 Silverado 6.5 diesel and the truck has a mind of its own. Sometimes when traveling down the road, the truck will just shut right off like it ran out of fuel or the fuel pump shut off. It doesn't really stumble like running out of fuel , more electrical because it is instant. Also, when stopping somewhere and coming back out to start it, the truck may take several attemps to start it. Once running it runs great. We have checked the obvious including connections, changed filters and have even dropped the tank to check the pickup tube and replaced the sending unit. The injector pump was also replaced recently before he bought the truck.
Does this sound like the fuel pump going? Thanks.

My buddy has a '96 Silverado 6.5 diesel and the truck has a mind of its own. Sometimes when traveling down the road, the truck will just shut right off like it ran out of fuel or the fuel pump shut off. It doesn't really stumble like running out of fuel , more electrical because it is instant. Also, when stopping somewhere and coming back out to start it, the truck may take several attemps to start it. Once running it runs great. We have checked the obvious including connections, changed filters and have even dropped the tank to check the pickup tube and replaced the sending unit. The injector pump was also replaced recently before he bought the truck.
Does this sound like the fuel pump going? Thanks.

Does the engine quit all together or just go to a idle?
I would get a fuel pressure gauge on it and check fuel pressure to injector pump.
Check ign voltage to injector pump and basic stuff.
Does it ever turn on check engine light?
Any codes?

The truck shuts right off. That is why I am thinking electrical. No codes either. I don't know if this is a symptom of a fuel pump going. If it was something electrical though, why after sitting does it not want to start? You would think if there was a loose connection or something it would have to be jarred to get it to start. Possibly the fuel pump getting hot and shutting down? I don't know Chevy's setup.

Proper testing.
See if it is losing fuel pressure or voltage.
MT