99 S-10 Pickup wont start

Here's my problem, my 1999 s-10 pickup(4.3 L)just will not start. I have replaced, cap and rotor, fuel pump, MAF sensor. This was all done to fix a hesitation which it did correct. (It was the MAF sensor which was my problem.) Had it running for a week until it just died on me. Now it will just turn over and over but will not catch. (will start on a prime but dies)I have tested fuel pressure and it's fine and theres lotsa spark. Thought it might be the fuel pressure regulator but was told it's not the problem. Something is keeping the injectors from firing.
Anyone got any ideas they can share?

try security codes