Ok here it goes. I have a 94 f250. It had been sitting awhile before I bought it. I couldn't get it started. I had good spark,good fuel pressure. So I put injector lights on it. I only had signal to one Bank of injectors. The four I had signal to were lighting up nice and bright. I suspected a driver for the other bank in the ecm was bad. Bought a new ecm and all injectors pulse now. However, the lights are dim as if the injectors aren't getting enough voltage to open the injectors. I can run the engine on starting fluid. I have checked all the grounds going to the ecm and they are all good. The voltage is good to all the injectors. If I jump the control wires at the ecm plug, on each bank of injectors, to ground all injectors light up nice and bright (which made me suspect a bad ground to ecm). I checked voltage with multimiter aswell as to not just rely on lights. So the wiring to the injectors is good and the power is there. I suspected a bad grounds to the ecm. so ran a jumper from the negative battery terminal to all the ecm grounds to bypass all the grounds and make sure they were good. Same thing. When I crank the engine over the lights are pretty dim and not operating as they should. I feel like I had tested voltage and grounds at this point. Everything seems to be there until you try to start it. I checked voltage on the pip wire at the ecm plug pin 56. I have 12 volts at rest and when I crank it over I have 4-5 volts as the engine cranks. So it appears to be getting signal from the distributor. Kinda lost any ideas. I have researched alot and searched forums. I have tried about any test I have read about and everything seems to be testing good. Thanks

 

I am thinking your new ECU is not so good.

 

I tried a different ecm and it does the same thing so I have two different ecm doing the same thing

 

maybe a bad ign switch?

 

Problem could be in the engine wiring harness, that's what's connecting your PCM to the injectors. Have you proven the harness good with a multimeter? If not get a wiring diagram matching your year and start checking the harness. I betcha there's some kind of problem in there.

 

Remove the connector to the Ignition Control Module (ICM) then recheck the PIP signal. My manuals states the PIP signal should be between 3-8 VAC while cranking, but I suspect yours may not be a true square wave or the ICM is dragging it down enough that the computer is not triggering the injectors properly. This is where an oscilloscope would be very handy.

The engine is firing up with starter fluid because the ICM is most likely triggering off the raw PIP signal.