Here is something to think about. This is from actual experience, no hearsay. I had one of our Blazers in the fleet that wouldn't start without starting fluid. I know that is a horse of a different color.
Fuel pressure was 52 psi at the fuel rail. Absolutely would not start on its own. A shot of starting fluid and you could drive it all day until you turned it off.
A new fuel pump relay did not help so I put a new fuel pump in it and started everytime at 60 psi. Problem solved.

Will it start with a shot?
James