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4.0 swap Simplify harness


BrettBrecklin

New Member
Joined
September 27, 2020
Messages
2
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0
City, State
Appleton
Year, Model & Trim Level
92 Explorer
well yes kinda
I mean when you strip all of the wires that are not needed, you end up with only a handful of wires that actually talk to and from the truck
There are wires that go to the fuel tank to power the pump, and for the emissions stuff
Then there are some wires that go to the dash, instrument cluster, and gem module
So yes I have done this plenty of times, basically when we do drivetrain conversions we strip the drivetrain wiring down to the bare essentials.....leaving just what is needed to interface with the truck and power distribution

In the old Gen I trucks like these the engine and trans wiring is a big mess, its routed along with the headlights, HVAC stuff, and underhood wiring.
IN 95 they finally changed all of that, the engine and trans harness became way more "stand alone" with just about every wire needed to run the engine and control the trans running through the single 42 pin plug on the back of the intake..........

My 88 BII still uses much of the 1988 dash wiring, but it has been stripped down to the bare essentials. I removed all 1988 power distribution and charging. Also 1988 lights and power doors were removed and replaced, also the charging system, wires all removed and replaced with custom.
I am running a 93 4.0 power distribution box and charging system which has been stripped down to the bare essentials (2 relays and 4 fuses)
Then I have the 97.5 5.0 wiring harness stripped down to the bare essentials and grafted in......

So at the end of the day all that is really needed to make a stripped down Gen I 4.0 run is fuel feed and return, power for the pcm, power for the alternator voltage regulator, ignition wire for starter control, and a few others.
The transmission controls are basically all handled by the pcm, back then it was just 1-2 solenoids a kick down cable and vacuum modulator.
Very simple system

You would not believe how many wires are NOT NEEDED to make one of these run
Personally if I am going through this much trouble I would convert the Gen I to be OBD2, and skip all of that. Just strip down a 96-01 4.0 harness to the bare essentials, deal with or delete pats, and add a OBD2 port to the truck side of things.....it really is a much much better system for transplanting.
Thank you for the reply!
I build these trucks to be run in demolition derbies, so there are a lot of things not needed.. gauge cluster, emissions, fuel pump wiring,, etc. The transmission only needs first and reverse really.

Was just wondering if you knew what wires absolutely had to be there for the truck to run. I saved the pictures of your hand written notes, which should come in handy..also thanks for providing those!



well yes kinda
I mean when you strip all of the wires that are not needed, you end up with only a handful of wires that actually talk to and from the truck
There are wires that go to the fuel tank to power the pump, and for the emissions stuff
Then there are some wires that go to the dash, instrument cluster, and gem module
So yes I have done this plenty of times, basically when we do drivetrain conversions we strip the drivetrain wiring down to the bare essentials.....leaving just what is needed to interface with the truck and power distribution

In the old Gen I trucks like these the engine and trans wiring is a big mess, its routed along with the headlights, HVAC stuff, and underhood wiring.
IN 95 they finally changed all of that, the engine and trans harness became way more "stand alone" with just about every wire needed to run the engine and control the trans running through the single 42 pin plug on the back of the intake..........

My 88 BII still uses much of the 1988 dash wiring, but it has been stripped down to the bare essentials. I removed all 1988 power distribution and charging. Also 1988 lights and power doors were removed and replaced, also the charging system, wires all removed and replaced with custom.
I am running a 93 4.0 power distribution box and charging system which has been stripped down to the bare essentials (2 relays and 4 fuses)
Then I have the 97.5 5.0 wiring harness stripped down to the bare essentials and grafted in......

So at the end of the day all that is really needed to make a stripped down Gen I 4.0 run is fuel feed and return, power for the pcm, power for the alternator voltage regulator, ignition wire for starter control, and a few others.
The transmission controls are basically all handled by the pcm, back then it was just 1-2 solenoids a kick down cable and vacuum modulator.
Very simple system

You would not believe how many wires are NOT NEEDED to make one of these run
Personally if I am going through this much trouble I would convert the Gen I to be OBD2, and skip all of that. Just strip down a 96-01 4.0 harness to the bare essentials, deal with or delete pats, and add a OBD2 port to the truck side of things.....it really is a much much better system for transplanting.
 




1sicbronconut

Elite Explorer
Joined
March 31, 2019
Messages
54
Reaction score
43
City, State
Rapid City
Year, Model & Trim Level
1968 Ford Bronco
exactly
start at the power box and the non needed plugs like ABS and start removing wires one at a time.
I like to clean the whole harness before I begin to cut the conduit and tape off
Yup one wire at a time!! I'd get a sheet of plywood and some saw horses to build a table. I've rebuilt quite a few EFI harnesses for early Bronco's, I used the table and actually fastened the harness in place to the table in roughly the way it will lay in the vehicle to help keep everything in perspective.
 




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