4.0 swap Simplify harness

[410Fortune]

You can do it!
I bought my BII for $500 from my dad, it had a terrible miss and had sat in the barn for a year
I drove it daily for more then 20 years then I built a 4 door explorer to help with daily duties and towing.
My BII sat (barely driven) for like 3 years because multiple issues stacking up and Colorado?Denver will not emissions with 35" tires. So we moved to ID 2 years ago and I started to get her back on the road. Now I am daily driving her again and it feels so good! The 4x4 is just plain awesome...had to use yesterday to take kids to school in blizzard conditions, YEAH!!

I have the same dash/body harness she has always had, all 1988 in there. I have modified it quite a bit, first it was 2.9, then 4.0 with stick, then 4.0 with auto, then finally 5.0 with auto....same wires on truck side.

You can do it!! Once you have it all mapped out on paper, then you start cutting things on the truck side so you KNOW where each wire is going and WHY

 

[Robert A. Peltier II]

I have all the wiring books from 89-94 and then some other various books and schematics as well
I will share with you some 4.0 wiring info that will be very helpful, I might have to get the papers and scan them in
I have piles of notes from each conversion I have done over the years.....

The power dist box gets many wires removed, as does the big white plug, and just a few from the engine harness
Most of the wires you take out will be from the dash, power, under hood ABS type stuff.
I routed ALL the wires on my BII along the back of the engine, nothing through the intake or around the front core support...much cleaner this way

I'm in the process of doing a 4.0 swap with an 85' Bronco II and a 92' Explorer. I have the 4.0 in and mounted to the B2 manual transmission, just started to put wiring harness from Explorer in and the big white plug appears terrifying-any help would be greatly appreciated.

 

[Robert A. Peltier II]

I have all the wiring books from 89-94 and then some other various books and schematics as well
I will share with you some 4.0 wiring info that will be very helpful, I might have to get the papers and scan them in
I have piles of notes from each conversion I have done over the years.....

The power dist box gets many wires removed, as does the big white plug, and just a few from the engine harness
Most of the wires you take out will be from the dash, power, under hood ABS type stuff.
I routed ALL the wires on my BII along the back of the engine, nothing through the intake or around the front core support...much cleaner this way

I'm in the process of doing a 4.0 swap with an 85' Bronco II and a 92' Explorer. I have the 4.0 in and mounted to the B2 manual transmission, just started to put wiring harness from Explorer in and the big white plug appears terrifying-any help would be greatly appreciated.

 

[410Fortune]

well you should actually be removing the big white plug, identify the wires in it and find their mates in the 1985 body harness
There are only like 16-20 wires in a 1985 truck that talk to the dash
You will need to convert the 85 to fuel injection, some sort of BII fuel system I would use a 89-90 BII system they have a single in tank pump just like a 92 explorer
I have wiring info for the 92 explorer big white plug, you should start a thread of your own so we can see what you have going on and help you!

 

[Robert A. Peltier II]

well you should actually be removing the big white plug, identify the wires in it and find their mates in the 1985 body harness
There are only like 16-20 wires in a 1985 truck that talk to the dash
You will need to convert the 85 to fuel injection, some sort of BII fuel system I would use a 89-90 BII system they have a single in tank pump just like a 92 explorer
I have wiring info for the 92 explorer big white plug, you should start a thread of your own so we can see what you have going on and help you!

ok thanks, I have the fuel system worked out using 86-88 B2 new parts & fuel lines from the Explorer donor

 

[410Fortune]

allright the 86-88 Bronco II uses a boost pump in the tank and a high pressure pump on the frame rail, this system is a real PITA
I also have a 1988 Bronco II
What I did was remove the high pressure pump from the frame rail and simply added a second fuel filter in its place
Then I installed a 89-90 Bronco II sending unit in the fuel tank along with a 89-90 BII pump in the tank
This is a much better setup then the dual boost pump, high pressure pump setup...........
I took it a step further when I went v8 back in 2005
I now have a 93 explorer sending unit grafted to a 88 BII drop in tank setup, using a walbro 255lph pump....I used the 93 explorer sending unit because nobody makes an aftermarket fuel gauge that will work with the voltage signal from the 88-85 BII and I do not have factory gauges.
I also cut an access panel in my cargo area so I can easily replace the fuel pump, this way I don't get stranded on a trail....
BII's kick ass

 

[Robert A. Peltier II]

much appreciated-ill jump on that option

 

[Robert A. Peltier II]

Looking for similar assistance in regards to wiring everything up. 85' B2/92' Explorer, really overwhelming

 

[410Fortune]

You need the 1985 Bronco II wiring book
You need the 92 Explorer wiring book
Then identify the wires on the truck side (there will be a few plugs coming out of the firewall below the brake booster) these are the wires that talk to the ignition, dash, and fuel system
Make a map of each wire color, circuit number, and destination

Now do the same thing for the 92 Explorer big white plug and you will see all of the wires on the 85 side of things will have a match on the 92 side of things

use the 85 style plugs and attach the pins to the 92 wires so you create a 92 harness that plugs into a 85 truck.
You will need to convert the 85 to fuel injection
You will also want to remove all of the 85 under hood wiring, alternator charging circuits and power wires.....leave the headlights and light wiring in place.
You should plan to add the 4.0L power wiring to the 85 under hood as the 4.0 is expecting to see a EEC relay, fuel pump relay, power feeds for the internal fuse box, and more

.

 

[Robert A. Peltier II]

You need the 1985 Bronco II wiring book
You need the 92 Explorer wiring book
Then identify the wires on the truck side (there will be a few plugs coming out of the firewall below the brake booster) these are the wires that talk to the ignition, dash, and fuel system
Make a map of each wire color, circuit number, and destination

Now do the same thing for the 92 Explorer big white plug and you will see all of the wires on the 85 side of things will have a match on the 92 side of things

use the 85 style plugs and attach the pins to the 92 wires so you create a 92 harness that plugs into a 85 truck.
You will need to convert the 85 to fuel injection
You will also want to remove all of the 85 under hood wiring, alternator charging circuits and power wires.....leave the headlights and light wiring in place.
You should plan to add the 4.0L power wiring to the 85 under hood as the 4.0 is expecting to see a EEC relay, fuel pump relay, power feeds for the internal fuse box, and more

.

Much appreciated-I'm that far, just need to figure out the wiring, so to the books I go.

 

[410Fortune]

So once you have the books the notes I posted on page 1 will be really helpful
The BWP (big white plug) for the 92 is listed in detail with each wire color and circuit number and destination.
If you need any more details from those notes as you get deeper in just let me know
First things first, I clean the harness, cut all the factory wrapping off and then get ready to start labeling wires that stay and removing wires that don't

 

[Robert A. Peltier II]

So once you have the books the notes I posted on page 1 will be really helpful
The BWP (big white plug) for the 92 is listed in detail with each wire color and circuit number and destination.
If you need any more details from those notes as you get deeper in just let me know
First things first, I clean the harness, cut all the factory wrapping off and then get ready to start labeling wires that stay and removing wires that don't

ok, much appreciated. I pulled the harness from the explorer last night for the fuel pump and there's obviously a couple of leads that wont be needed (ABS/limited slip) that I noticed right away. I'm waiting for the pump (88-90 b2) to see what end it'll need so I can change if needed. I glanced at the diagrams for a few minutes, never had to do this, so a bit overwhelming at this point.

 

[410Fortune]

one wire at a time
start with pin 1 on the BWP locate it in the 92 book and follow where it goes, write it all down
In 20 years your notes will look like mine!!

 

[Robert A. Peltier II]

one wire at a time
start with pin 1 on the BWP locate it in the 92 book and follow where it goes, write it all down
In 20 years your notes will look like mine!!

Not seeing what I need in the book I have other then the general diagrams, not the plug itself. Also need the info for the 85' B2 wires in the firewall that I need to join up to. So frustrating.....

 

[ghosttrain2]

finished a 4.0 swap in my '86 Bronco 2, used a '94 donor, and converted from an A4ld in the Bronco, to a 5 speed. I also have the wiring books for both, the '86 one was about useless. Too many wire colors that didn't match the book. Having been a dealer mechanic when these were new, made this easier. I used the underhood fuse box, pulled out the unneeded fuses and relays'.I have been driving it, and it is a whole new truck with the 4.0.

 

[410Fortune]

yeah it makes you wish the BII never came with a 2.3, 2.8 or 2.9...if they were all 4.0 then they would never have been given such a bad wrap!
Well done!!

 

[ghosttrain2]

A/C is charged and working, Cruise control adjusted and working, all the '86 gauges and tachometer working just fine with the 4.0. Love it!

 

[BrettBrecklin]

There is a lot of great tech in this thread!

410Fortune, I'm trying to build a standalone harness to run the engine and trans for these early 90s Explorers. Have you ever built one that only runs the engine and trans?

I've got a 92 in the shop right now that runs, but is junk. I was tinkering with the harness earlier today and got a little over zealous cutting wires at the big white plug. Do you know off hand the bare minimum wires to run the engine and trans?

 

[Norvyn Martinez]

"A/C is charged and working, Cruise control adjusted and working, all the '86 gauges and tachometer working just fine with the 4.0. Love it!"

Man, I love it when everything goes according to plan!

 

[410Fortune]

410Fortune, I'm trying to build a standalone harness to run the engine and trans for these early 90s Explorers. Have you ever built one that only runs the engine and trans?

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.