1993 Chevy S-10 Wierd fuel pump problem

I have a 1993 S10 pickup. It has the 4.3 A/T 4x4. The truck has 214K milse on it and has been ultra dependable until about two weeks ago. I drove the truck approx 30 mi. Stopped in a parking lot when I went to leave it would not start. The fuel pump was not running. OK so I am there for about an hour foolong with the relay & the wirtes checking them over and suddenly it decides tyo run. I drove it home shut it off and then it would not start. I replaced the oild pressure switch, the pump relay, and the distributor (the shaft had excessive wear & play in it). The truck ran great for about for days then the same thing drove it about 30 miles shut it off & was at the place for about 2 hours came back out & again no fuel. The pump is approx 3 years old from NAPA & the sending unit is less than a year old it was a new GM part. The ECM is sending power to the pump even when the pump does not run. The grounds are all tight so could it be a problem with the new sending unit or perhaps the pump getting weak? I am stumped on this one. PLease help.

Update. I have tried running power directley from b the battery both with the trucks test lead and by fabing one myself. The pump will come on sometimes but not always. Almost like it has a bad ground, but the they are clean & tight. I think it must be some problem in the tank with either the pump or the sending unit. Just can't figure it out and did not want to pul the tank out without knowing for sure. Thanks for all the help so far.