The CJ Build – Motor Wiring Harness Upgrade

New wiring harness install

(this time it’s the motor compartment)

Now that I was finished with the inside of the Jeep, it was time to tackle the hard stuff… the MOTOR! YIKES!!

To start off here…if you’re building a jeep up like I was…be sure to have the fenders ready to put on and take off at this point (if you have stock style fenders that is, not a flip front end) because you’ll need to mount several things to the fenders of your Jeep that will have to be wired and to get the wires looking and fitting nicely, obviously the stuff has to be physically mounted where they’re going to be when you are finished to get a nice fit. So at this point, I put on the fenders and started to go to work… this was tricky because I had to go back and forth between the two manuals I had (haynes and chilton) and the factory wiring harness schematic that I found on the internet somewhere, and also the information in the painless manual…I had to make sense of ALL that stuff and combine it into something that would work on MY Jeep…. ugh, this isn’t going to be fun.

first step for me was to get the headlights and turn signals and parking lamps wiring setup and DONE so I didn’t have to deal with those extra wires hanging around when I was dealing with the important wiring for the actual engine, charging and starting systems. I ran the wires just like I had before on the back side… farthest point first…so I started with the passengers side lights and moved to the drivers side lights and ran all of the wires through the grille in ONE split loom for all of the lights and horn circuits. Those wires all ran along the drivers side fender at the top and I used clips and zip ties to hold them all in one place. Here’s a shot of the loomed wires on the drivers side of the engine compartment:

Notice how there is that one wire hanging out that is green, right on top of the fender? That is for the horn circuit, I just left it hanging there but tied it up until I got to installing the horn so it was up out of the way for the rest of the process.

When I was wiring the headlights and taillights and all…I had to know how to wire the headlight switch…and I THOUGHT I would be able to do that with no problems. I mean, I had several schematics to work with right? How hard could it be? It was a bit of a frustrating experience because there were several times where I thought I had it nailed, and then when I would step on the brakes, the brake lights wouldn’t come on, unless I had a blinker turned on… WHAT is THAT all about? GRRRRRRR getting mad now. Anyway.. once I used my trusty multitester to pin-out the headlight switch…it was apparent that there needed to be TWO sources of power going to the headlight switch to make things work correctly…one for the headlights BY THEMSELVES and one for the rest of the systems (like parking lights and dome light and gauge lights….etc. Finally I got it figured out…I will post it here once I get it marked up on the picture I have.

Ok, now that the lights were done (much testing throughout this process by the way) and they worked correctly… Time to get the rest of the thing going! Where to start? Well, as usual, I just picked something farthest away from the wiring bulkhead and went to work.

I picked the alternator and starter circuits… those are pretty straightforward really. Just hooked it up like the wiring diagram from painless performance told me to. The only thing I had to figure out was where to put the master fuse that painless provides in their kit. it’s a 50A blade fuse in its own little housing..and you put it in line with the alternator and battery circuits so that if something gets overloaded it pops the fuse instead of blowing up your battery or something bad like that happening. It’s also pretty easy to do and painless marks everything out VERY well in their instructions. At this point…here’s approximately how my engine compartment was looking:



You can see from the picture above, I had the standard ignition system..and the little silvery looking box at the bottom of the picture (mounted on the passengers side fender) is the idle control circuit. My jeep is an automatic and it is the Laredo package which means it has air conditioning also…so they had to have a way to bump up the idle when the vehicle was in gear, because that causes the idle to drop on automatics..also, there needed to be a way to control the idle when the air conditioning compressor was activated so this idle control module is supposed to do that job… THIS THING is a pain in the butt to hook up, plain and simple…a nightmare. I couldn’t really find ONE diagram or schematic that exactly told me what wire did or went to what in the rest of the jeep in any detail…so it was time to assimilate all the manuals together and hoep it worked out. HORRIBLE! So I just took what I could find that this thing was connected to in the OLD wiring harness ( remember I said that I was glad I didn’t throw it away, this was one of the reasons why!). Once I got it hooked up… I just threw my arms up in the air and hoped for the best to be honest. I still am not sure it is hooked up correctly to this day (but as you’ll learn later in the’s not even being used anymore).


SO, then it was time to wire the distributor and ignition system circuits… here’s where life gets really annoying REALLY quick. AMC used the Ford ‘duraspark’ ignition system in 1982 Jeeps apparently, and I had the joy of trying to figure out which wires went where… On the distributor, there were two lead jacks coming off, one split and went partly to the coil/ballast resistor and partly to the ignition switch somewhere in the interior. The OTHER one went to the ignition module, that was conveniently located on the OTHER side of the motor and it in turn was half wired to the distributor and also had 3 other wires coming off in ANOTHER jack that went to who knows where…the ignition module was brilliantly placed under the windsheild wiper water reservoir and the antifreeze coolant reservoir. Who was designing this? Well, I worked for a couple of days, maybe a week on this, doing LOTS of research on the web and reading through all of the books and schematics that I had. I also called Painless a couple of times, and I have to give them props, they helped me out with a few things that I had NO clue on, I was desperate and called them and got one of their techs..and he helped me figure some stuff out over the phone. PAINLESS PERFORMANCE Techs are AWESOME!!!!

So, I got it mostly figured out according to the manuals that I had and the help from Painless, and the internet research…So I go out to the garage the next weekend….put some gas in the tank and prime the carb (at this point I’m using the piece of junk stock carb, the CARTER 2BBL) and try to fire it up just to see if I can get some spark and get it to run for a minute or two at least… I still didn’t have a whole lot of stuff hooked up, like the fan clutch or horn or any accessories, but I wanted to see if I could get it to run at this point.

So, I turn the key and it starts to crank…. keeps cranking strong (I got an 800 CCA battery from the local O’Reilly Auto Parts so I had PLENTY o juice to crank it over AND get spark). But….

NO SPARK = NO RUN (I knew that dura-‘junk’ would fail in the long run!) Ok, on to the next project…this one ticked me off so I needed to do something else while trying to figure out what to do next with the ignition system.

Continue on with the Ford Taurus cooling fan upgrade…