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Hey ya'll! My wonderful MJ died on the road last September and sat at home unloved for the winter, so it's time to get it running again. This is what I've done/discovered so far. I replaced the fuel pump since it no longer primed when I turned on the ignition and assumed that was the problem. Fuel gauge has never worked and it turns out the floater on the old pump had broken off, so I hope the new one will let me know how much gas I have. I refreshed the ground behind the tail light following cruiser's instructions, and will eventually relocate the ground to the fuel filter, but the ground is now good. I ordered the big 7 from jeepcables.com and will be doing that this week. I've determined the fuel pump relay is good and cleaned the connections. I've gone through the grounds and discovered the the braided line from the engine the chassis is gone! Could this be a possible fix? The fuel pump is definitely good when I use a probe and give it direct power. Basically I'm at a bit of a loss as where to look next. The engine cranks just fine but the fuel pump is not getting any power even to prime it when I turn on the Ignition. Maybe a fuseable link? I'm going to put in a proper fuse/relay box from a 90's cherokee in there eventually, but I just want the thing running again so I can at least move it/work on it in the garage when the weather is bad. Any help is appreciated :) If you need more info ask away and I'll do my best to answer Goddamm Renix jeeps man...

FullSizeRender.MOV So I went to boost my truck few days ago and I accidentally put the booster cables on backwards and then got in and turned it over, it made a horrible zing noise from the starter and my gauges went all crazy, I got out and changed the cables to normal and the gauges went back to normal but now it just turns over and sometimes starts and idles fine and even Revs fine but dies after 5 seconds, my relays also have a clicking to them after I try start it. All my fuses look fine and I even have Ksuspensions 250A fuse between the fuse block and the alternator and it blew so maybe that saved something. I already put in a different fuse block and didn’t change anything. I attached a video of the truck running fine but right after he video stops the truck dies instantly IMG_7300.MOV IMG_7300.MOV

I'm making progress on my 86. This week I repaced the fuel level and oil pressure senders, so all of my gauges are working. The last thing I need to fix on my project that is critical is my instrument illumination. Here is the story: When I turn on the illumination via the headlamp switch I do not get any instrument lights. The clock illumination goes out. Not dims, mind. Out. Turn off the headlight switch and it comes back on. I have voltage at the illumination fuse, and the voltage varies when I turn the headlamp switch. So the switch is good. I have power to the clock and cigarette lighter. Since gauges, radio, and lighter work, I have no indication that the grounding is poor. I do not have a working warning buzzer - though it WAS working recently. I have removed the radio, so there cannot be any issue with how I wired the radio. My best guess is that there is a problem with one of the circuits that connects to the dimmer switch. My first thought is to pull the radio/clock illumination relay, and see itfthat helps me narrow down the problem. According to my repair book, the relay is located "under l/h side of I/P, behind kick panel". The wiring diagram shows it wired to the harness at a point very close to the horn relay. I found the horn relay, but I don't see the illumination relay. Or anything that looks like one, nor do I see a socket for one. At this point I'm rather flummoxed. I CAN rewire the illumination directly, but I'd like to identify and fix the existing problem if possible. So I'm looking for suggestions as to what to try. And if anyone knows where the #&$#^$ illumination relay is, please let me know!

86 mj My oil pressure guage does not work properly, and I can't diagnose it. It reads high all the time. I got out my troubleshooting manual. First step. Disconnect the sensor, and the meter should read high. Check Seconds step. Ground the wire, and it should read low. Check. If it does, Third step: replace the sensor. Check Result: It still reads high. T o my way of thinking, assuming that the brand new sensor is good, somehow the electrical circuit is open, but I can't see how it could be. The only place I can think of is that the sensor itself is not properly grounded, and that seems, well, impossible. I'm open to suggestions as to what else I can try, or should look at. I mean, there i s really is only the guage (which seems to be working) a wire, and a sensor....

I'm totally puzzled. My Comanche is a 1988 and when I turn on the headlights, the tail lights and running lights don't come on, but when I put my foot on the brakes they do come on. Also when I'm towing my trailer, the trailer running lights don't come on unless I put my foot on the brakes. It's not a fuse and I just replaced the switch clearly not the switch. Where is the ground so I can check it next?

Hey y'all. Due to this pandemic I'm out of the job and have loads of time for my comanche project! Hurray! I bought my 87 with a lot of electrical issues and a bad motor. While I sorted out the motor with a used 96 high output, the electrical issues are driving me nuts. Here's my main issue: No turn signals on either side, no illumination on the dash indicators. The hazards do work fine though. I've replaced a few parts and don't know where to go next. It has new turn signal switch (not fun) and a new turn signal fuse, as well as a new negative battery cable. I've yet to go through some of the grounds and that's what I plan on fiddling with today, but I was wondering if there is anything else I should be looking into? There's also a weird thing going on where the driver side brake light is always on even when the car is completely off. In order to keep the battery healthy and the bulb from burning I have it on a battery maintainer but I'm not sure if this is pointing me to the real problem or is a different headache altogether. Thanks for any help/advice!

So the 10A fuse for dash lights/running lights/buzzer for having the key in on my 90' Comanche blows when I insert the key. If I put a fresh fuse in and turn the lights on without the key in the dash lights and running lights work, the second I put the key in the fuse pops. So would this mean whatever makes the buzzing noise for leaving the key in is causing this? Or is the ignition bad or what, what should I look for?

Do Wiring Diagrams change for each year? I have a 1988, will the 1987 (70 series) 8980 010 491 work?

I have a 1989 comanche eliminator. Inline 6, 4x4, AX15, 3 inch lift. Been driving fine. Just bought it a couple weeks ago. Has a bit of high idle. Leaks here and there. Smallest amount of coolant in oil but it does have 268k miles. Gonna do the head gasket and such soon. I drove it and parked it, no problem. Blinkers stopped working but was going to look in to that. Been following Cruiser54's tips for sprucing up grounds, adding some, etc. Will keep doing them as i go. The next morning after i parked it in my swamp of a driveway, it wouldnt start. Normally i turn the key and the pump primes, its loud. I can hear it while driving but it seemed fine. Definitely noticeable. This time, no prime. So being before work i didnt do much besides bang on the tank and switch the relays around, nothing. After work, i checked ballist resistor, 1.1 ohms, bypassed anyways to no avail. The relay was swapped around with all the rest so that rules out the relay. I checked for power at pump, i get 6 volts off of the plug for pump with key in on position. I'm thinking that's kinda low. I also get 6 volts if i hook up the wire (bypassed ballist resistor) to my meter and ground it on body. So I'm sure its getting to the pump but maybe not enough? I also did Cruiser54's tip of adding a independent ground on the pumps harness just to be sure as well as clean ground behind taillight housing. I have power on pin 30 of relay and switched ignition power on pin i believe 85 (trying to remember what pins are what). I tried jumping power to the pump and that didn't work. I also removed the pump (before i added the extra ground point to it) and hooked it to the battery for a split second, and it did run. So I'm positive the pump itself is okay. Right now I'm working on tracing wires and connections and sprucing up plugs, etc. I tried looking around other forums, etc for ideas but I'm not sure at this point. Any ideas or thoughts would be greatly appreciated.

I have a new alternator to put into my mj - as soon as the weather warms up a bit. But I need a bit of insight into how the alternator hooks up to the wiring. This could be a stupid question, but here goes: The wiring diagram shows three wires connecting to the alternator. Looks like they go to battery, ignition, and instrument cluster. My jeep only has two wires actually connected at the alternator, battery and (I assume) ignition (since it will start) There is a third wire, but it is not connected to anything at the moment. I have not yet begun to explore the intricacies of the electrical system on this project, so I'll leave that for now. So my question relates to the non-battery wires. My new alternator is internally regulated and has connections for "field" and "stator" (along with the main battery connection). Which one would the instruments hook into? Since there does not seem to be electrical connectivity, when at rest, between the battery terminal and either the stator or field connection, how does the ignition switch get power? Do I hook the switch wire directly to the battery connection?

In adding a decent winch to my beast, I'm looking for advice about my charging system. 1) is there any easy way to tell which alternator (I understand that there were different models with different outputs) is in my truck? 2) What is the largest battery anyone has shoehorned into the normal location? 3) Any recommended battery? 4) If a second battery is added, where does one put it? (Just trying to consider all my options) 5) in wiring the winch, is it preferable to runa ground direct to the battery, is is it ok to ground to the frame? Thanks in advance for any assistance

So I recently bought an 88 2.5L from a guy that had put a lot of effort but no money into keeping it running. Cheap aftermarket guage cluster when sensors would fail. Push button light cause the dash lights would cut out every no and again, local bike cable release cause the hood cable broke. Fiberglass and chip board cause the floor rusted through. All that aside it started and ran alright best I could tell. Replaced the ignition system(starter relay, coil, cap, rotor, plugs, wires) Drove it for about 1000 miles then went after some other repairs. Traded the ax5 from my 89 that is a parts truck now for the ax4 that was in it. Replaced some faulty wires, Seemed like it was running well, well enough. Charged up the AC (which he wired a direct switch to the compressor for cause I guess the climate control failed.) Drove it home from my buddies where we were working on it. I was sleep deprived and loosing it on my hour drive home, made it home safe, but only just barely. I recall that it began to run rough toward the end of my journey but not much more than that. I leave it for a couple of days as I had things that necessitated my GFs car instead of my own. I finally have time to look at it. I jump it because I left the compressor engauged and drained the battery, and my buddy yells at me that its shooting oil everywhere, the sending line from the aftermarket oil pressure gauge had been melted through and was shooting a perfect jet of oil up and into my hood which was deflecting it in every direction. This is my best deduction. The AC line burst (evidence of this is present) spewing Freeon and compressor oil all over my engine bay. It contained(or rather is) a solvent that spent the weekend eating through all kinds of plastics and rubbers in my engine bay including: The oil pressure line The black plastic cable path that contain every engine wire the boots to my brand new spark plug wires stripped the paint from my firewall and hood and left corrosion/aluminum salt built up on: alternator ac clutch bell for the fan water pump starter relay coil pack fusible link wires!?! What should I do? This truck was supposed to be a minimal amount of work while I cut the front off of my 89 rust bucket to fix the 90 4.0 that I t-boned a lady in. I have a 1hr 50 mile commute Cash is tight now but I am also trying to improve this as I go. The 4.0 is supposed to be my daily driver and I would like to have the 2.5 as a second little runner truck for employees incase they need to take some equipment across town, but having employees is a year away.

Okay so my problem started when I left my truck sitting for quite some time and when I tried to start it I found my battery was beyond gone, and the cables had corroded extensively. So I bought a new battery and cleaned up the cables quickly and started right up. A week later I try to start it and I got nothing, no crank, no fuel pump sound, and even more interesting no headlights (and yes new battery is good). I know these headlights are separate so I am thinking either multiple fusible links or starter relay? Also I have done Cruiser's ground refreshing tips in the past and also double checked the battery ground and dipstick ground this week. So what do you guys think? start with fusible links and starter relay in the morning? Also how do I test fusible links? backprobe with multimeter and test resistance? How can I test the starter relay as well? I am referring to the diagram here in this thread for the starter relay btw http://comancheclub.com/topic/49932-battery-short-to-ground-now-truck-won't-start/?hl=starter+relay&do=findComment&comment=508394 Thanks for any help you can provide 87 4.0L 4x4

I'm diving into some preventative electrical work in my '88 Pioneer. I've already done the C101 elimenation, and i'll be going through and refreshing ground and haress connections. The other item i would like to include is a replacement of the fusible links with a fuse panel which is fairly simple. The only hangup i'm having is the load ratings for the factory fusible link. I've searched through the wiring manual for the 88 MJ and i cannot locate an amperage rating. One option would be to size the fuses based on the wire gauge for the circuit. This seems a bit risky to me given the already poor Renix electrical system design. The wire gauge may be overkill for one of the components in the system leaving me at risk for a short in component, but not enough current draw to blow the fuse. The other option is to add up the amperage draw for all components in those circuits, based on the component fuses, and using that value for the fusible link replacement rating. I'd rather not have to do that... Does anyone know the amperage raitings for the fusible links?

I've started designing a new chassis wiring harness for my truck; partially in preparation for a tdi swap and partially because I've grown to really like wiring and electrical systems and just want it all fresh. I see there's a green fusible link feeding power to the switch and there's two outputs that feed the "run" position (one also feeds the "acc" position.) By counting the fuse ratings on the circuits fed by these two I come up with 32 amps on the "run only" output and almost 90 amps on the "run and acc" circuit! Am I crazy or is that really high?! The next question would be are these two portions of the switch rated to carry different amounts... I believe this is all GM stuff btw.

ok guys i need some help on deciding how I'm going to proceed with my swap. i have a 87 Jeep Comanche, I6 2wd 5spd stick. i also have a 96 jeep cherokee I6 4x4 Auto trans. I'm wanting to take these 2 and make my Comanche 4x4 with the auto trans, but I'm not quite sure how to do it. I'm doing this because my cherokee rusting out and has a salvage title and on its last leg, the comanche has perfect body and clean title Option one: lots of work, i swap the whole engine transmission t case and ALL the electronics ( harnesses computers dash ect) out of my cherokee into the comanche. this is allot of work and I'm a lil uncomfortable doing that because ive never done it and fear that ill screw it up. the other reason I'm leaning away from this is there is sighs of rigging in the electrical of the charokee before i owned it and i don't want to put bad electrical in, Option two: i take just the Auto trans and tcase and mate them to the engine in the comanche. if i do this i know i need a flex plate that matches my torque converter. But then i have to find some way to wire the auto trans up which i don't know how to do. any tips info or right ups on wiring a auto trans into a Manuel comanche or cherokee? all the help would be much appreciated!!

So when i start my truck, i have to jiggle the key to get the accessories to work (the HVAC, radio and turn signals/wipers) Lately I'm not even able to get them to turn on while jiggling the ignition/key cylinder. I've replaced the cylinder and it still hasn't helped, Any suggestions?

I have an 88 Comanche with instrument cluster problems. The gauge readings are wrong or not reading at all except speedometer of course. I see a Instrument Panel Cluster Relay listed as a possible problem or fix. I can't find the location for the relay voltage regulator. Thanks.

Hello, unfortunately i am posting on here sooner than i intended. Tonight i picked up a 1988 MJ Pioneer, 4.0, 4X4, Manual, 114K Miles. About 50 miles into my 100 mile trip home, cruising along at 65mph, the engine completely died. There was no sputter or signs of charging system issues prior to the issue. I put the clutch in while still rolling and the engine did not crank, or have any sign of life. My headlights and dash lights did stay on the entire time. On the side of the highway i attempted to start the engine multiple times, but nothing moved, no sounds from the starter, solenoid, or fuel pump. Now for the history. The previous owner replaced the lock cylinder after someone busted the old one trying to steal the vehicle. He replaced it with a cylinder fromm a S-10 which i believe is a proper fitment. My theory is that there is a loose connection at the ignition switch. This would cause the system to act as though the key is not being turned at all. Unfortunately i am not too familiar with Comanches yet. I plan on checking fuses tomorrow night, then working my way through the wiring. I hoping the knowledge base here will help put me on the right path to sorting out this issue. Nothing like a $250 tow bill introduction into Jeep ownership, Haha. :)

Need Help....I have a 1988 Comanche I've had for about (4) yrs. Truck has been running great, then decided not to start today. Engine will turn over but no start. I've check all battery connections and coil, getting power there but still no fire to the plugs. Distributor cap, rotor, plug wires were changed just a month ago. Any ideas??

Hi I just bought a Comanche that I have been looking for a long time because I wanted to make sure it was the right one. last it was registered was 6 years ago but runs great and was started every couple of months really has been taking care of, although the fuses look fine none of the things are getting power, no wipers, blinkers, tail lights and almost everything that has a fuse for it in the block , the fuses are fine its just like not getting power to all of them. I did see a red wire that was added to the fuse block that was cut and led no where, maybe used for lights or something. Please any kind of help would be much appreciated Thank You Ps - I'm stoked to be on this forum!!

It has been a long time coming friends. Here is a little background on this project... I drove to Alabama from Georgia to tow this beast home after looking for a long time. Got it for $900 in working condition with some "minor" fixes necessary. I guess "minor" is somewhat subjective, but here is a list of what I got, what was wrong with it, what I've done to fix it so far and what I'm planning on doing. Keep in mind that this is still in progress. I will keep you guys updated as it comes together with tons of pictures and probably some videos. I'm big on videos... Anyway, here's the beast the day after I picked it up: And here's some more pics before some of the fixes just to give you the full scope on this guy: And here's the engine: The rust was not terrible, but obviously not ideal either. The biggest issue was basically the electrical was all messed up. It would not start half of the time, the turn signals never worked when it did start, no radio, A/C worked only half the time, and worst of all, half the time I was driving and it would just stop if it idled. This was not an engine issue though, it was all electrical. I knew this because all power would go out and if I got out of the truck and wiggled the wires around, i could eventually get it to crank. I turned to ComancheClub to help me asses the issue by uploading tons of pictures of my wiring. While this wasn't a bad idea, it still was futile just because nobody could really see the issue. Turns out that there was a bad diode in the alternator. Check out how the last owner dealt with the alternator. I guess this is an Alabama fix? :doh: So, to start, I replaced the alternator and fixed some minor wiring issues. Now the turn signals work, the A/C works, the heat works, the engine cranks every time and stays that way no matter how long it's idling. :banana: Alright, so the beast is alive now. Good progress. From here some routine stuff had to be addressed. The radiator fluid inside of the overflow was rust brown. I flushed it completely and then found out there was a huge leak in the radiator. I guess some dirt or rust was clogging the hole up before, but now it was just pouring out coolant. So...time for a new radiator. :wrench: After I got the radiator in, I went to the oil, changed the filter, put some good synthetic stuff in there. Food for the soul . :MJ 1: . So...now the beast runs like a champ with a new alternator, fixed wiring, new radiator, new coolant, fresh oil filter and clean oil. So what's next??? :) Here's my list. This will allow me to have something to reference as well as allow you guys to hound me if I'm not updating you with pics and info! -Paint Job, sand down the rust -Take out the carpet and fix the floor as I'm sure there's plenty of rust there. -I know the interior looks pretty good, but I have an itch to change the interior to some sweet black and white seats I saw on this forum a ways back. I will try to find some photos, but am not sure I'll be able to. But it looked sooo good. -Add roll bars -possibly a lift -Needs new tires desperately -Some surprise customization that I'll keep you all on the edge of your seat for :popcorn: Normally, a paint job shouldn't be the FIRST thing for a variety of reasons...but I had an opportunity that was too good to pass up to trade a guy who has a paint shop for services. I build websites, do photography, video etc. so I offered to build him a couple websites for his business if he would paint the beast. He agreed. Under 1 condition though...he will paint it textured flat black (kind of like a bedliner paint job...) At first, I wasn't crazy about this, but I actually went to visit a jeep that had this paint job...and I think it looks like a tank. Pretty freaking cool I think. But...just want to throw that out there so you guys don't think I killed my jeep when it comes back murdered out! B) I think it will look good...at least it will be a unique look. Anyway, I'll hopefully be able to update you guys next week with the paint job pics. Stay tuned

Hello all! I posted a ways back about a new comanche I was lucky enough to find. Right now there is one extremely daunting task that I am debating turning over to a mechanic, but I wanted to stop by here first to see what you guys thought, because I trust this forum way more than most of the mechanics that would be giving me quotes. For instance, I spoke with one on the phone today that stopped me and said "I already know what the problem is. You don't have to say anything more. You need an entirely new wiring harness and need to re-wire everything. Going to run you about $2,400 and anyone that says they'll do it for cheap is going to ruin your car". So, obviously I'm doing everything I can to not pay someone $2,400 because that sounds insanely ridiculous, but my issue is that if I dive into this wiring situation alone, I'm afraid my Comanche may not be able to be revived. There are far too many wires in this car and not that much information on the process from beginning to end. So! Below are lots of pictures of my current wiring set up as well as a detailed description of the problems I'm experiencing. I will be as thorough as possible in hopes someone can guide me in the right direction. I'm not opposed to fixing it, as long as there is something i can reference. But if you guys think this kind of situation is better in the hands of a professional, I'm willing to turn this one job over to a mechanic, but would prefer to know what it is that needs to be fixed so I don't have people telling me it's going to be $2,400... List of problems: -Crossed wires cause the car to not start or turn off every once in a while. After messing with the wires, it will restart. This seems to be occurring around the main positive/negative battery wires. -No turn signals. They worked once, haven't worked since. -A/C turns on half the time, half the time it doesn't -Horn works 25% of the time, 75% it does not work -Windshield wipers are on and off, but seem to be working more consistently now -Some kind of wire crossing caused my last battery to drain extremely quickly -oil gauge does not work Annnd I think that's mostly it. A lot of on and off stuff. Just want to get everything consistently working. Any thoughts on best solutions are welcome, cheapest options exceptionally welcome! https://imageshack.com/i/ip089f27j https://imageshack.com/i/f0e06cb5j https://imageshack.com/i/hla6bc5dj https://imageshack.com/i/p5e193b2j https://imageshack.com/i/ez529218j https://imageshack.com/i/p446cd16j https://imageshack.com/i/km221dbdj https://imageshack.com/i/f0ceea38j

So, driving home tonight the truck was running great until I was about 3/4 of the way home. Then the truck just randomly died. Lights stayed on, battery connections are solid, no engine code, just dead. Here's the weird thing. After it died, it took about five minutes and then it would start right up. BEFORE that five minutes was up, there was absolutely no power to the starter. No click, no grind, just nothing. My question to you guys is, what the hell could it be? I'm at a loss. I mean, POSSIBLY a ground wire, but then I would think it would kill the battery too and there would be no lights... I'm just at a loss. Let me know.

Hi All, I have a 1990 Jeep Comanche, 2WD 2.5L 4-Cylinder. Manual AX5 transmission. I've done some minor transmission / clutch work on it with plenty of help and support from the forum. Generally, it runs fine (now). But... Recently it's been doing two strange things: Losing power (shutting off) at low speeds, normally when jarred or bumped. It starts right back up when this happens. Most often, this can be seen when it's parked and I start it, then release the parking brake. When the parking brake jolts, the truck loses power. I have to re-start it. Also, on occasion, it loses power at low speeds (parking lots, mostly) often on bumpy terrain. It always starts right back up, but for the moment when the power steering fails, it's no fun. Lurching / losing speed while driving. When driving anywhere from around 30 to 55, it sometimes suddenly slows down a little -- just a mile an hour or two -- but very quickly, sort of lurching a bit. I can normally compensate by pressing the gas pedal down further, then it just sort of evens out. It never gains speed while lurching, only loses speed. And most often right around 40 - 45 mph. It feels like it's either losing power or gas suddenly -- but the truck doesn't shut off of anything. I recently (several weeks ago) lost power completely (truck wouldn't start) and found out that the main battery cable was corroded and much of the insulation had rotted off many of the cables. I got the truck running again with some electrical tape and a new clamp for one of the battery terminals. I imagine the above problems are related to electrical issues, but don't know how to troubleshoot them. The battery cable itself is very complex -- lots of wiring in there going who knows where. I also on occasion have some odd electrical issues -- namely the windshield wipers behaving unexpectedly and the turn signals staying on until fiddled with. Anyone have electrical experience on this or a similar truck? Do these all sound like electrical issues? I'd love any advice, tips, feedback or whatever. Thanks much, this forum has always been a huge help.