Ignition control module

I'm still trying to figure out why my Jeep won't start. I plan to change the CPS and bypass the ignition and install an on/off switch and start button, but I'm not sure which plug to tap into. If someone could help me with wire color/count, and plug shape that would be great. It's an 88 XJ with a 4.0L and AW4.

I'd love to get a picture of the plug I think I need to tap, but with the Jeep sitting stationary for so long, a family of snakes has taken up residence, and I don't feel comfortable hanging my head under the dash in the dark until I'm sure they have all found new homes. Any snake wrangling techniques would also be helpful.

Perhaps you could explain your problem (ie, cranks but won't start, nothing happens when you turn the key, ect??) Hate to see you start hacking away at the wires... Year, engine would help too.

Any good mongoose worth his salt will take care of your snake problem. LOL

As I stated in the orig. post it's an 88 XJ with a 4.0L. I forgot to mention that NOTHING happens when I turn the key. The door buzzer stops, the horn/lights don't work, it dosen't click or try to crank. It has a brand new starter, and the charging system was checked just before the last time I drove it in January.
I don't plan to start "hacking at wires" that's why I want to make sure I have the right harness to start with. Once I can get the thing in my garage and start on the next phase of the build I'd like to rewire the whole thing with good quality wire and soldered connections.

As far as security without a key, I don't drive the thing on the highway, I don't leave the battery hooked up while it sits, and I have a hidden switch for the fuel pump planned for when I have it parked at the campground when I'm wheeling. I could keep the mongoose after the snakes are gone and use that as a theft deterent as well.

In a warm evening, just when it´s turning dark, start a small smoky fire, with appropriate insulation (a brick and tin can), to save the carpet. Snakes are most active, when it´s warm, and start hunting in the early evening. Try not to make so much smoke, it stains the headliner, but pretty thick. Leave the snakes a way out, open the doors after awhile. If the snake has just eaten, it may not want to move, may take a few repeats to get them out. Ferrets, work as well as Mongoose and are more abundant.
I´d be tempted to fix what I have and do some systematic tests to find the problem (ignition switch/fusible link?). Rather than, adding switches and cutouts. It would be way, to easy, to interrupt one system and drive the current through another system to ground, with often really strange results. Thats one of the reasons the ignition switch, is a multi contact.

bbaker80 said:

Any snake wrangling techniques would also be helpful.

Click to expand...

A number of yeras ago a family of garter snakes founf their way in through a chink in the stone masonry and took up residence in the gap between the metal "Heatilator" firebox and the stonework of the chimney. A local veterinarian who is a noted snake expert advised me to put moth balls or moth crystals in any crevices I could see.

I guess it worked. I didn't see any snakes after the mothball deployment.

check the primary ignition box-aka: solinoid- right behind the battery- if this box go`s bad, it`ll do this.

Doh... I see now that you did mention the year/eng. Because obviously I'm kinda :dunce: let me just clarify, you have power unil you turn the key to the start position, then you lose power? If that's it, check your negative cable off the battery. A crappy gound there is one possible explantation for that problem.

I agree. Mine did that off and on for about 2 years before I found the problem. It was a loose negative battery cable connection, where it bolts to the engine block. It was only finger tight, and I suspect it had been that way from the factory. (Probably why the original owner traded it)

it sounds like the battery is ok if the door buzzer is working. if is an automatic i would bet it is the neutral safety switch. do you reverse lights work?

A quick check of the battery is the horn. It pulls 30-40 amps and if the battery isn't good the sound will start to change immediately. The grounds are a big thing, the ingition switch is also a prime suspect.


If it just doesn't crank, put a volt meter or light on the small green wire that controls the starter and have someone turn the key. The light should come on. If that works, move the light to the big power wire on the starter and do the same thing. If the light comes on, you have a bad starter, if it doesn't you either have a bad cable or a bad solenoid up by the battery.

I had a similar problem with my 87 with aw-4 just a couple weaks ago. Mine was a bad nuetral safety switch. It's real easy to diagnose, unhook the black(thats the ground) wire from the start relay (the NSS is wired in series with the ground wire) and take a jumper wire and connect one end to the ground lug on the start relay and the other to the negitive battery terminal. This by-passes the NSS. If it still does'nt turn over I'd guess the start relay or ignition switch is bad. To test the start relay, pull the "sol" wire off the the start relay, hook up one lead from a digital volt meter to the "sol" lug of the start relay and the other wire to ground. Have somebody hold the ignition switch in start. If you get 12volts, then both the start relay and igniton switch are ok, the problem is the wire to the starter solinoid or the solinoid/starter. If no volts, pull the "ign" wire of the start relay and hook up the voltmeter to this wire(this wire comes from the ignition switch). Have your helper again hold the start swith in start, you should have 12volts, if not, bad ignition switch or open wire.