89 gmc 2500 5.7l will not start but will run

I have done almost everything to fix. replaced fuel pump,fuel pump relay,oil press sw,tps,map,ecm,rebuilt fuel press regulator on tbi, will start once in awhile but will not stay running at idle. in starting mode no power to injectors. if i prime tbi will run as long as you keep rpms above idle but as soon as you go to idle it dies! please help before i tear my hair out or spend every pennie i have

Welcome to AF. How about the basics, vacuum leaks, iac not working to manintain idle speed, any misfire, Find the issue of no power to the injectors when cranking first. Wiring diagrams at autozone.com, repair guides.

The injectors on this truck get there signal from the ignition modual and pick up coil under the distributor cap. I have seen a truck about the same year have spark but no signal to the injector, it ended up being the ignition modual. Hope this helps.

thank you for your reply. i failed to mention i replaced IAC also. no vacuum leaks have been found.

thank you for your help. I believe that is correct.I will purchase ignition module tomorrow what do i have to lose ? its just money! that will be quite amazing if it is the I.M. that throws anybody a big curve first thing i checked was spark! I really appreciate the help from everyone!

The injectors on this truck get there signal from the ignition modual and pick up coil under the distributor cap. I have seen a truck about the same year have spark but no signal to the injector, it ended up being the ignition modual. Hope this helps.
bought ignition module started right up purred like a kitten. thank you very much and learned valuable lesson not everything is as it appears and my truck has a lot of new parts.