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BBF swap wiring issues

I have a 1994 F-150 that originally had a 4.9L E4OD with 220K. After developing a miss that I could not resolve, I went for an engine swap. I was able to find a 1997 F-350 7.5L that had the 5spd removed(price was right). I pulled the Engine and harness. Purchased a rebuilt BBF E4OD and a junkyard ECM from a 92 F-250 7.5L auto. We originally tried to used the engine harness from the 94. We had 41psi at the injectors. We had ground, but the injectors would not pulse. All fuses and relays had power in both blocks. We tried the ECM that was mated to the 97(we weren't worried about powertrain at this time. Just wanted to fire.) Nothing. We had good spark and were able to communicate thru the Snap-on Analyzer. We had the engine fire over off of starting fluid. I pulled the 94 loom and after changing a few plug ends, installed the 97 loom(OBD1 to OBD2). This time, we lost fuel pressure. The pumps(dual tanks) were not energizing. Checked fuses and relays again. All good. We were able to jump across the relay and get the pumps to energize. We had power to the injectors, but with a test light connected, there was no pulsing when cranking. Whatever the root cause, we are assuming now that it may be ignition related. It is a new ignition switch that was installed when trying to correct the misfire in the original engine. Any input would be greatly appreciated. Started this [simple swap] back in September.


Staff member
Check for any disconnected grounds. I had my 88 shut me down over that. It had a ground at the battery that wasn't connected. The injectors are pulsed by controlling the ground, not power.

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