Trouble with an 'ol PSD

[Longshot270]

I'm posting this question for my dad who has a '97 7.3L with an automatic tranny.The truck is completely stock and has never had to go to a shop except to get a code cleared. We did have some tranny trouble a few months ago but that was from a funny random code that caused the truck to enter the limp home mode (as mentioned earlier). No troubles after we had the code cleared until now. The trouble he is having now is the engine will just stop ever so often. I've ridden with him and it has happened one time when I was there. Heres what happened; we were driving and the engine just stopped turning. There was no jarring or jumping the moment before, the rpm just went to zero and the truck kept rolling. One curious thing I noticed was how smooth it stopped, it was smoother than if you were in a parking lot idling and turned the key off normally. Then after it shut down we pulled over and tried cranking it again. We turned the key and it started back up like nothing happened. This has happened with the engine cold(50 or so degrees), warm, pulling a trailer, completly unloaded, accelerating and cruising so there aren't any specific conditions that trigger it that I can see.

Here are the questions he wants me to ask:

1) How many fuel pumps does the truck have? He suspects that there may be more than 1 pump because the problem only happens with the back tank, NEVER the front.

2) What are some other things that could cause this to happen? We both suspect that it is something electrical because of how crisply the engine shut down.

Like I said the truck is completely stock and has been take care of VERY well. We dont have a code reader so I have no idea what codes, if any, are present.

Any insight into this issue would be greatly appreciated.