been working on 91 f150 for few days now. truck runs but no injector pulse on bank 1 injectors. no pulse coming from ecm have fire on + side of injector

 

If there is no injector pulse at the injectors, then you need to trace it back to the PCM. The Tan wire from pin 58 is the trigger for the Bank 1 injectors.

courtesy of oldfuelinjection.com

A simple continuity test will tell if the circuit is intact or the injector driver inside the PCM is bad. I suspect a broken wire or bad connection.

 

wiring is good checked at injector connector to pin 58 0n breakout box. replaced ecm with one out of running truck of same year

 

I would venture to say you have a bad PCM in light of the symptoms and troubleshooting you have completed so far.

 

thought the same thing replaced pcm with one from running truck still same problem tried ignition module just to see if any change knew better but when your pulling hair youwill try anything

 

If there is continuity between pin 58 on the EEC connector to the negative side of each injector, via the Tan wire, then you really have a head scratcher. One item that comes to mind is checking the continuity between pin 58 and ground. Perhaps there is pinched wire. Another thought is that +12V you measured on the positive side of the injector is not really there, it' s phantom measurement. A common false positive caused by using a high impedance Digital Volt Meter (DVM).

I recently had the same thing bite me in the butt on my Bobcat. Thought I had voltage from the battery up to the control panel, but in reality I had an open circuit. This is a good example why some folks suggest using a test light. I now have one in my toolbox.