BBF swap wiring issues

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Jan 23, 2023 | 11:49 AM

booboo26003

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8th Gear

Joined: Jan 2023

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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.

Jan 23, 2023 | 12:21 PM

Scndsin

FTE Chapter Leader

Joined: May 2006

Posts: 12,324

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From: Central Mississippi

Welcome to FTE.

It's only simple if you stay within the model year of original truck. The engine doesn't really matter.

100% harness/color codes for engine, ECU, etc.

Following cause I've always wanted to see somebody do it & document it.

Good luck & maybe some recommendations later.

The 97 ECU is not playing/going to play with the 92 E4 because diode mismatch

Jan 23, 2023 | 12:51 PM

booboo26003

Thread Starter

8th Gear

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I'm waiting on an ignition wiring diagram. Was told to check for crank signal(we had it with 94 harness). Was told that the modules are different. I'll post anything that I find

Jan 23, 2023 | 03:21 PM

rla2005

Fleet Owner

Joined: Oct 2005

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From: Kentucky

Here is the ignition diagram for a 1997 F25HD/F350:

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Jan 23, 2023 | 03:28 PM

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,785

Likes: 1,751

From: Kentucky

Quote:

Originally Posted by booboo26003

Was told that the modules are different.

Yes they are different as well as some of the wiring. The 1992 uses a Push-Start style ignition. There is a 22K ohm resistor that develops the Ignition Diagnostic Monitor (IDM) signal back the the computer. There is also a signal from the Start circuit that goes directly to the Ignition Control Module (ICM) that retards the timing during crank. A 1997 uses a Computer Controlled Dwell (CCD) ignition that uses a black colored ICM that develops it's own IDM signal back to the computer. There is no Start signal going to the ICM or computer. The low RPM during cranking, sensed by the PIP sensor inside the distributor, is interpreted as cranking so the computer retards the timing.

If you have no spark, even with the SPOUT unplugged, then you are most likely missing the PIP signal. With the SPOUT unplugged the computer is no longer controlling spark via the ICM, the ICM will trigger off the raw PIP on it's own.

Jan 24, 2023 | 09:13 AM

booboo26003

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8th Gear

Joined: Jan 2023

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Quote:

Originally Posted by rla2005

Here is the ignition diagram for a 1997 F25HD/F350:

Thank you!

Got it running. Sounds rowdy. Was a bad ground.
Sounds pretty feisty

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Jan 24, 2023 | 12:11 PM

OBS460

Logistics Pro

Joined: May 2022

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From: Everywhere and nowhere

Is the 460 MAF? You stated the 97 harness was OBD-2. If going from a 97 with a manual trans I would think you need a 97 computer for and auto trans. The E40D is computer controlled and if the 460 is MAF and you are using a speed density computer from an older year I would expect issues.