1994 GMC Sierra 4x4

I purchased a 1994 GMC Sierra 4x4, 5.7 L
extended cab with a TSI motor from a friend. The
truck had been sitting for 4 years outside. I worked
on the brakes and exhaust. I drove it for a couple
days putting very little miles on it and it died. I
noticed that when I'd shut it off and start it again it
would run, but after a handfull of times doing that
it once again died. I replaced a fuel line I noticed
that had a leak, along with filter. Gas was flowing,
pressure was good. Fuel pump good as well as
fuel pressure. It doesn't start but acts if it wants to.
I can check the pressure regulator and the second
temperature sensor I didnt know about until now. I
have another TFI motor to work with, so if you
know what might be causing this problem and the
easiest way of doing it, it'll be greatly appreciated.