Beachbum1236 Posted June 2, 2008 Share Posted June 2, 2008 Hey guys! Well things wen t from bad to worse, but The problems been found and I need a new CDI box. Was wondering if anyone knew where i could get one, and how much they usually run. will i be able to use one out of another year 2.5 or another engine in general? I've got an 86 2.5 Thanks for the help! Link to comment Share on other sites More sharing options...
mvusse Posted June 2, 2008 Share Posted June 2, 2008 I always thought CDI stood for Common rail Direct Injection, which is diesel technology. What the heck is a CDI box for a gasoline engine? Link to comment Share on other sites More sharing options...
Eagle Posted June 2, 2008 Share Posted June 2, 2008 Wait, wait -- I think I got trapped on this one before. Bahamas. Is your MJ built to U.S. spec, with the throttle body Renix ignition/injection system, or is yours built to the 84-85 spec with a computer-controlled carburettor? Link to comment Share on other sites More sharing options...
Beachbum1236 Posted June 2, 2008 Author Share Posted June 2, 2008 Wait, wait -- I think I got trapped on this one before. Bahamas. Is your MJ built to U.S. spec, with the throttle body Renix ignition/injection system, or is yours built to the 84-85 spec with a computer-controlled carburettor? It's the Renix system. TBI. the entire thing just died when i was out with my sister and a friend on the back roads. friend was positive the CDI was done for so i had a mechanic look at it just to make sure, and it was in fact the CDI which had gone. Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 2, 2008 Share Posted June 2, 2008 I am still waiting for a confirmation on what a CDI box is as I have never heard of that... :hmm: Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 2, 2008 Share Posted June 2, 2008 It's the Renix system. TBI. the entire thing just died when i was out with my sister and a friend on the back roads. friend was positive the CDI was done for so i had a mechanic look at it just to make sure, and it was in fact the CDI which had gone. Do you have an aftermarket capacitor discharge ignition box wired in? That's the only thing I can think of. :nuts: Link to comment Share on other sites More sharing options...
maddzz1 Posted June 2, 2008 Share Posted June 2, 2008 eagle, i think this is thread from before http://www.comancheclub.com/forums/view ... ht=bahamas Did you ever find out if it was an export version or run the vin number? Link to comment Share on other sites More sharing options...
Eagle Posted June 3, 2008 Share Posted June 3, 2008 I'd like to know how the mechanic determined it was a failed CDI -- whatever that is. Any time a Jeep with a CPS dies (and the Renix TBI does have a CPS), that's almost always the problem. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted June 3, 2008 Share Posted June 3, 2008 a CDI is an engine computer. CDI is what is used to control the engine on say a snowmobile or motorcycle. it's a small engine version of an ECU. so he's swapping terms here i believe. either that, or he really just means CPS but i doubt that. Link to comment Share on other sites More sharing options...
Beachbum1236 Posted June 3, 2008 Author Share Posted June 3, 2008 Do you have an aftermarket capacitor discharge ignition box wired in? That's the only thing I can think of. crazy I'm not sure if I have one of these, I haven't really taken a look at all the wiring in the truck yet. not sure where it would be either. Did you ever find out if it was an export version or run the vin number? It's an export of the US, import to here, same as the States cars/trucks. headlights are a pain though, everyone drives on the opposite here, and they don't bother to alter them. so theyre right directly in your eyes, and they have their brights on. a CDI is an engine computer. CDI is what is used to control the engine on say a snowmobile or motorcycle. it's a small engine version of an ECU. so he's swapping terms here i believe. yes, sorry, this is what i was talking about. sorry for getting the terms mixed up. too much outboard engine work. The ECU controls all the power from the battery which allows it to be passed to the started, ignition coil, etc etc. I don't even have power to the radio or 12v plug. although i do have a full charged battery?????? sorry again for the confusion! Link to comment Share on other sites More sharing options...
Eagle Posted June 3, 2008 Share Posted June 3, 2008 The ECU controls all the power from the battery which allows it to be passed to the started, ignition coil, etc etc. I don't even have power to the radio or 12v plug. although i do have a full charged battery?????? sorry again for the confusion! I do not think that's correct. I am quite certain that the ECU does not control power to accessories like the radio or 12v plug, and I'm pretty certain it doesn't control power to the starter. I think you need to start tracing your power circuits, starting at the battery, following the battery cable to the power distribution block on the right front fender, and from there through the wiring harness. This does NOT sound like a bad ECU. I would also consider inspecting the ignition switch. On the Comanche, the place where you insert the key in the steering column is not the electrical switch. There's an operating rod from the key tumbler down the column. The actual switch is located near the base of the steering column. That switch, or the wiring connected to it, sometimes goes bad. If that's the case, turning on the key may not be energizing any of your circuits. Link to comment Share on other sites More sharing options...
Pete M Posted June 3, 2008 Share Posted June 3, 2008 It's technically possible for a computer to go bad, but it's a rare event indeed. Link to comment Share on other sites More sharing options...
Eagle Posted June 3, 2008 Share Posted June 3, 2008 Oh, I agree that ECUs can go bad. But on an 86 MJ the ECU doesn't control power to the radio, cigar lighter outlet, or starter. But the ignition switch does ... Link to comment Share on other sites More sharing options...
mvusse Posted June 3, 2008 Share Posted June 3, 2008 If your headlight work (they bypass the ignition switch) I would also suspect the switch first. If the switch is fine, check the fusible links. And of course battery cables/connections and ground straps. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 4, 2008 Share Posted June 4, 2008 a CDI is an engine computer. CDI is what is used to control the engine on say a snowmobile or motorcycle. it's a small engine version of an ECU. so he's swapping terms here i believe. either that, or he really just means CPS but i doubt that. What? CDI is a capacitive discharge ignition system, not an engine computer. It's an alternative to a pulse discharge ignition system. CDI systems have been around since the 50's, and as you stated are commonly used on smaller 4-stroke engines, like motocycles, snowmobiles, etc. CDI ignition systems deliver a higher voltage to the coil primarys w. basically zero delay, thus are also used on racing engines for hotter spark. Companies like MSD and even Mopar sell add-on CDI boxes for any high performance vehicle especially for drag racers. It has nothing to do with engine computer control functions except to deliver spark to the plugs with less delay. Link to comment Share on other sites More sharing options...
james750 Posted June 4, 2008 Share Posted June 4, 2008 So its basically like a super fast magneto on small engines? And does it replace distributor and electronic ignition systems on multi-cylinder engines? I'm very confused right now. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 4, 2008 Share Posted June 4, 2008 Here's an example of MSD's universal offering. http://www.msdignition.com/new_products/5520.html Motorcycles/snowmobiles/lawnmowers, etc. mostly come standard with CDI systems. Just surf mate. Link to comment Share on other sites More sharing options...
Beachbum1236 Posted June 4, 2008 Author Share Posted June 4, 2008 hmmmmm, okay. :oops: apparently, i don't know whats gone wrong. but hopefully someone can shed some light on the problem after i explain just what happened. Out one day about a week and half ago. on some rocky roads, potholes here and there, and suddenly the truck just dies. were like okay, well, maybe it stalled, and doesn't want to start. we then try to jump start it about 3 times, and that doesn't work. so we begin pushing it to town. on the way there we were trying to figure out what had gone wrong. Well I knew the battery was good because I have 12V lights for the interior hood up straight to it. Okay so i've got power, the next thing i noticed was that I had a 12V fan that I could plug directly into the 12V plug. I plugged it in, turned it on, turned the ignition on, and nothing happened, but on occasion it would turn over very slowly. So somewhere there was power, but not nearly enough to make things work. My buddy then put a screwdriver down to the starter motor and pressed against the terminals. the motor turned, but there was no spark. (I know it isn't the safest thing to do, but thats how we do it here if something doesn't want to start or if were right there and the key is 10ft away and don't feel like getting up.) We both knew it was an electrical problem, somewhere something was blocking the power to everything. Well his dad is a great mechanic, and he's pretty good at engines, better than i am. And he suggested that it was probably the CDI box (ECU) not managing power to all of the components. Thats what it usually is on boat engines, CDI box goes and theres no power to anything which can cause it to not start. Apparently there is also a pretty new ignition switch in the truck, so i and skeptical about the problem being that. I was although the same day, messing around with the new radio, (someone stole the other i had put in) and there were some loose speakerwires, and i think there was either an orange an d black'purple one, and a Purple with an orange stripe also loose. I hae no clue which one that was dangling went to, the scematics in the Haynes manual didn't really help and the colors on the radio are totally different, so maybe something could have shorted out? does this help in anyway of trying to locate whatthe problem is???? Thanks guys, and sorry for the unclear and wrong statements before :cheers: Link to comment Share on other sites More sharing options...
james750 Posted June 4, 2008 Share Posted June 4, 2008 Maby he thought you had a CDI instead of a STANDARD ignition system. take some pics of the ignition system so we can see if you have a CDI. Link to comment Share on other sites More sharing options...
87ComancheLB Posted June 4, 2008 Share Posted June 4, 2008 If the truck was running fine until you hit some @$$ big potholes, then it leads me to believe something got disconnected or more or likely got shorted to the chassis and discharged the battery or something got damaged. I will be looking for that, before changing out any electronics components. Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 4, 2008 Share Posted June 4, 2008 Yeah...I would say to go over all of the battery cables and ground straps VERY carefully. After a couple other converstions on here about the same problems, the issue was found to be bad/loose battery and/or ground cables. ;) Don't just "look" at them...grab them, pull them, bend them and make sure the connections and cables are good. Link to comment Share on other sites More sharing options...
Eagle Posted June 4, 2008 Share Posted June 4, 2008 ROFLMAO That reminds me of an incident from the dim, dark ages of my youth. I had driven a friend home after basketball practice one cold, dreary winter night, and my car stopped dead in the middle of the road on the way from my buddy's house to my house. This was, of course, eons before the invention of the cell phone, so I hiked back until I found a house with lights on, knocked on the door, and was allowed to call home. My father came over. The car was DEAD. No horn, no lights, no gauges, no turn over -- NADA! We couldn't figure out what was happening, because it had been running just fine, right up until it quit. I was tired, I was cold, I was frustrated. I finally got so mad I hauled off and kicked the left front tire (did I mention I played soccer?). THE LIGHTS CAME ON! Turned the key, the car started, and I drove home. Turns out my helpful little brother did me in. The weekend previous, we had pulled the battery and done some cleaning up in the engine room. L'il bro' reinstalled the battery, and he forgot to tighten the bolt on the frame end of the ground wire. Oops. Lesson learned from making the same mistake too many times: NEVER overlook the simplest, most obvious possibility in the rush to embrace the most expensive possible repair. Hint: Google "Occam's razor." Link to comment Share on other sites More sharing options...
Beachbum1236 Posted June 5, 2008 Author Share Posted June 5, 2008 I just got some new information today. Something got shorted, pretty sure it's CDI (ECU.) Apparently, the battery jumped out of it's holder and shorted out on the underside of the hood of the truck. I had a marine battery which i though was okay, no problems, same typical batter as usual. NOPE, theyre taller than stock car batteries, and because the terminals are on the top it also makes it a bit higher. My buddy who worked on it noticed this and put a small carpet between the battery and the hood so it wouldn't touch. Although he didn't tell me this and i ripped the carpet from under the hood and threw it in the bed. I've hopefully found a replacement CDI box and i hope that this will fix the problem. hopefully in the next few days i'll be able to replace it and let you guys know the good or the bad news. thanks for the comments! :cheers: Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 5, 2008 Share Posted June 5, 2008 Yep...that'll kill an ECU. You will be the second one on here to kiil one in that same manner in the last few weeks...if that is your problem. Link to comment Share on other sites More sharing options...
Beachbum1236 Posted June 6, 2008 Author Share Posted June 6, 2008 okay so, I've been searching around and I happened to find an ECU on ebay. It's from an MJ 5 speed 2.5 litre, but it's a 91 model, not an 86. I was wondering if this could possibly fit, or does it have to be the exact same year? any responses would be greatly appreciated! Thanks!!! Chris Link to comment Share on other sites More sharing options...
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