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Unread 04-02-2010, 06:30 PM   #1
Tshark299
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1987 YJ Wrangler 
 
Join Date: Mar 2004
Location: Upstate NY
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4.0 Swap - Bulkhead Connector Wiring List

There have been a few threads lately where people are asking which wires to keep and which wires to change when swapping in a 4.0 so I typed up my wiring notes from when I swapped out my '87 4.2 for a '95 XJ 4.0. I'm not sure if someone else has already done this, but from the number of questions I've seen lately I figured it couldn't hurt to share what I did as clearly as possible.

As most have figured out, all wires in the right side of the bulkhead connector feed front lights, horn, etc., and do not need to be touched. This list will only deal with the left side of the connector.

"(12 - BLK/RED)" means black 12 gauge wire with red tracer
"(18 - YEL/)" means yellow 18 gauge wire with tracer (usually black or white)
"(18 - VIO)" means violet 18 gauge wire (no tracer)

1987 YJ Wires That I Kept in the Bulkhead Connector:
C6 (18 - YEL/): Provides power to the backup light switch.
F4 (14 - ORN/): Connects to heater blower motor.
C5 (18 - GRN/): Connects to negative side of ignition coil for tachometer signal.
F5 (18 - LT GRN): Connects to oil pressure gauge sending unit.
C4 (18 - VIO): Connects to temperature gauge sending unit.
A4 (20 - GRY/): Connects to low brake pressure switch near master cylinder.
B6 (18 - GRY/): Also connects to low brake pressure switch.
H6 (18 - BLK/): Connects to 4WD indicator switch.
G6 (18 - BRN/): Takes power from backup light switch for backup lights.
E5 (16 - PINK/): Provides power for under hood lamp.

"XJ E4 to YJ D4" means I removed the wire from cavity E4 on the XJ bulkhead connector, and inserted it into cavity D4 on the YJ bulkhead connector.
"PDC" means Power Distribution Center (engine bay fuse/relay panel from XJ).

1995 XJ Engine Harness Wires I Connected to YJ Bulkhead Connector:
XJ E4 to YJ D4 (12 - RED): Always hot, provides power from PDC fuse 6 (labeled 'Ignition System') to ignition switch.
XJ H2 to YJ G5 (18 - YEL): Hot in start, provides power from ignition switch to PDC starter relay.
XJ D2 to YJ G4 (12 - BLK/RED): Always hot, provides power from PDC fuse 7 (labeled 'Heated Window') to interior 'Rear Defroster' fuse.
XJ C4 to YJ B4 (14 - DRK GRN/TAN): Provides power from PDC relay B (labeled 'Fuel Pump') to the (you guessed it) fuel pump. Of course you'll have to add a fuel pump, but the wiring is already back there for one.
XJ B6 to YJ D5 (12 - DRK BLU/YEL): Hot in run and start, provides power from ignition switch to PDC fuse 11 (labeled 'Ignition').
XJ D1 to YJ E4 (12 - RED/WHT): Always hot, provides power from PDC fuse 5 (labeled 'Headlamps') to interior Headlamp, Dimmer Switch, and Parking Lamp fuses.
XJ G4 to YJ B5 (12 - BLK): Provides grounding from engine compartment to instrument panel.

Additional Wires I Ran:
From ECM pin 32 (20 - BLK/PNK) to dash for Check Engine Light.
From ECM pin 36 (20 - DRK GRN/YEL) to dash for Check Gauges Light.
From ECM pin 54 (20 - ORN/BLK) to dash for Up-Shift Light.
From PDC 'Radiator Fan' relay (16 - LT GRN) to my electric cooling fan.

It seems like a lot of people fear the wiring for these swaps the most, but after I spent some time mapping out the diagrams it didn't seem half bad. This is how I have mine set up and it started right up on the first try, and everything inside and out works 100%. Hopefully this info helps out others working on similar swaps.

__________________
'87 YJ Laredo - 4.0L, AX-15, NP231, 4.10s: 3.5" BDS, 31" Muds

'95 XJ - Donated drive train to the YJ, Parted out the rest

'51 CJ-3A - Buick 225 V6: Painless Wiring Harness, Warn Overdrive & Hubs, 2" Lift, 31" Muds

Last edited by Tshark299; 04-02-2010 at 06:49 PM..
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Unread 04-02-2010, 08:49 PM   #2
yjcrawlr
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Nice list t-shark!
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90 YJ 102 in wb stretch, SOA, dana 60, 14 bolt welded,4.56s, 37in Parnelli jones dirt grips, currie twin stick dana 300, york oba, tractor link traction bar, full custom armor,poison spyder tube fenders, 95Cherokee High Output 4.0
2014 JKU, modified Rubicon Rails, RC stubby with warn 8000m, 2" leveling springs and OME trim spacers, Superchips Flashcal, Spidertrax wheel spacers, rubi shocks, and Lots more mods soon!!!
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Unread 04-03-2010, 09:35 AM   #3
Tshark299
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Quote:
Originally Posted by yjcrawlr View Post
Nice list t-shark!
Thanks man. I don't remember seeing any lists like this before I did my swap... although I'll admit I didn't really look that hard. I had the wiring diagrams for both vehicles so I just went through and made a chart. I just came across it last night and though hey, maybe this will save someone else some time.
__________________
'87 YJ Laredo - 4.0L, AX-15, NP231, 4.10s: 3.5" BDS, 31" Muds

'95 XJ - Donated drive train to the YJ, Parted out the rest

'51 CJ-3A - Buick 225 V6: Painless Wiring Harness, Warn Overdrive & Hubs, 2" Lift, 31" Muds
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Unread 06-21-2010, 01:58 PM   #4
A4T1Rat
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Great List. I am trying to get ready to do my swap 89 yj 4.2 to 94 cherokee 4.0 and this will help. Thanks
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Injection is nice but Ide rather be Blown
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Unread 06-21-2010, 05:06 PM   #5
dodger889
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T where did you mount the ecm?
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A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
Quote:
Originally Posted by bigsquat View Post
im just cheap, and cheap makes you creative.
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Unread 06-21-2010, 05:37 PM   #6
Tshark299
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Quote:
Originally Posted by dodger889 View Post
T where did you mount the ecm?
I mounted the ECM on the driver side fender, similar to where it was on the XJ. There is a groove on the inside of the fender that it fit pretty well in. Using the XJ wiring harness, it's easier to put it up there than in the stock YJ location under the brake booster on the firewall. I can get a picture of it if you need.
__________________
'87 YJ Laredo - 4.0L, AX-15, NP231, 4.10s: 3.5" BDS, 31" Muds

'95 XJ - Donated drive train to the YJ, Parted out the rest

'51 CJ-3A - Buick 225 V6: Painless Wiring Harness, Warn Overdrive & Hubs, 2" Lift, 31" Muds
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Unread 06-21-2010, 05:38 PM   #7
Tshark299
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1987 YJ Wrangler 
 
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Location: Upstate NY
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Quote:
Originally Posted by A4T1Rat View Post
Great List. I am trying to get ready to do my swap 89 yj 4.2 to 94 cherokee 4.0 and this will help. Thanks
You're welcome!
__________________
'87 YJ Laredo - 4.0L, AX-15, NP231, 4.10s: 3.5" BDS, 31" Muds

'95 XJ - Donated drive train to the YJ, Parted out the rest

'51 CJ-3A - Buick 225 V6: Painless Wiring Harness, Warn Overdrive & Hubs, 2" Lift, 31" Muds
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Unread 06-21-2010, 10:46 PM   #8
dodger889
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Quote:
Originally Posted by Tshark299 View Post
I mounted the ECM on the driver side fender, similar to where it was on the XJ. There is a groove on the inside of the fender that it fit pretty well in. Using the XJ wiring harness, it's easier to put it up there than in the stock YJ location under the brake booster on the firewall. I can get a picture of it if you need.
OK I was just wondering It sounds like where I put mine.
__________________
A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
Quote:
Originally Posted by bigsquat View Post
im just cheap, and cheap makes you creative.
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Unread 08-23-2010, 10:01 AM   #9
freakmonkeydog
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Location: OKC, Ok
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So did you keep your 4.2 wiring harness and just swap those wires you listed at the bulkhead?
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Unread 08-23-2010, 08:20 PM   #10
dodger889
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Join Date: Jan 2009
Location: mi
Posts: 4,161
Hooked up to the 4.2 wiring harness and married two together chased down the wires for temp and oil. Now for the tach you will need to run that to the negative on the coil. Change the oil pressure and temp sensor for the gauges to work.
__________________
A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
Quote:
Originally Posted by bigsquat View Post
im just cheap, and cheap makes you creative.
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Unread 08-24-2010, 12:04 PM   #11
freakmonkeydog
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1987 YJ Wrangler 
 
Join Date: Sep 2009
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Quote:
Originally Posted by dodger889 View Post
Change the oil pressure and temp sensor for the gauges to work.
Change to what, the 4.2 sensors?
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Unread 08-30-2010, 01:59 AM   #12
ImpactFabWorks
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Location: victorville,ca
Posts: 1,864
This should be put in the FAQ section. This is one of the most common swaps out there and this the first decent wiring list I have seen
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Unread 08-30-2010, 06:21 AM   #13
dodger889
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Quote:
Originally Posted by freakmonkeydog View Post
Change to what, the 4.2 sensors?
Yes change the sensor from the 4.2to the 4.0 engine.This way your factory gauges work.
When you add you wire for the check engine light. The wire from the ECM is ground not a hot led. So one side of the light goes to the ECM and the other side goes to a hot switched terminal.
__________________
A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
Quote:
Originally Posted by bigsquat View Post
im just cheap, and cheap makes you creative.
dodger889 is offline   Reply With Quote Quick reply to this message
Unread 09-01-2010, 04:47 PM   #14
melvin1356
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Join Date: Aug 2010
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Posts: 7
i have seen several post talking about this topic and most of them have been dealing with the 4.0 out of a cherokee but not any that i can find dealing with a 4.0 out of a YJ. have you any information on the bulk head connector and what if any wires will need to be used for a swap from a 93 4.0 yj to my 87 4.2 yj
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Unread 09-01-2010, 06:10 PM   #15
dodger889
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1989 YJ Wrangler 
 
Join Date: Jan 2009
Location: mi
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The basic is still the same going from a 4.2 to 4.0 mfi ( yj or xj) you should get the wiring diagram from the donor vehicle and yours. Remember that no mater which one the engine comes from you need to be able to connect crank position sensor and the proper flywheel for the year of the engine.

The reason that the xj are being used they are cheaper to get the whole vehicle than yj.
__________________
A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
Quote:
Originally Posted by bigsquat View Post
im just cheap, and cheap makes you creative.
dodger889 is offline   Reply With Quote Quick reply to this message
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