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Won't start. No spark. Coil & Distrib. OK

9

90woodyxj

NAXJA Forum User
Location
Sebastopol, CA
So my Jeep crapped out a few weeks ago when I went wheeling. Had to flatbed it home. Decided to start trying to fix it today, and discovered that there is no spark, not even from the ignition coil. However on random occasion every great once in a while it WILL spark, but usually it does not. One person said maybe a camshaft position sensor?
Anybody else got any ideas to offer?
CPS is not even 6 months old.
1990 XJ, 4.0L I6
 
90woodyxj said:
So my Jeep crapped out a few weeks ago when I went wheeling. Had to flatbed it home. Decided to start trying to fix it today, and discovered that there is no spark, not even from the ignition coil. However on random occasion every great once in a while it WILL spark, but usually it does not. One person said maybe a camshaft position sensor?
Anybody else got any ideas to offer?
CPS is not even 6 months old.
1990 XJ, 4.0L I6
Click to expand...

Most people carry a spare position sensor.....it's a part that likes to fail with your symtoms.:wow:
 
I had a similar problem and it was a mess. The ignition switch was messed up and was sending low voltage which caused the CPS and relays to go bad then had to get my ECM rebuilt. Had to send it back about 7 times until it was right. New ECM $780.00 Rebuilt one $250.00. Had plans to modify the truck but that money had to go make it run again. Good luck in finding the problem.
 
oh boy, i hope thats not my problem. ive had some serious electrical problems in the past. i have a rebuilt comp for my jeep sittin around. oh, i think i forgot to mention this fourwheeling adventure it crapped out on involved LOTS of mud....
 
The thing with the CPS is that when it goes out, you still get spark, yes? I had to replace it once before, because a short in my system toasted it and I was still getting spark.
 
Since I just fixed my '89 today with the same symptoms, I'll chime in. 5-90 calls it the "renix killer" or ground strap. If it's shot, the renix computer won't even come on. Mine was in bad shape, replaced it today and started right up. Check it out for corrosion.
 
it runs from the back of the engine, i think cylinder head? to the firewall. it is a very common problem with the renix system. mine was in poor shape, replaced it and it started right up. i had it towed 2 days ago and wasn't getting any spark at the plugs. thanks to a few helpful folks on here i was able to find out that was all that i needed. 7 dollar part plus 65 dollar tow :(
 
ill definitely check that out tomorrow once its light and i can fiddle with that thing again. i was lucky enough to have a friend flatbed my jeep home when it broke down thank god.
 
Make sure the wires to your CPS are not burned through on the exhaust. I had this problem. It would run for a while and then crap out when the wire grounded. It's only 2 bolts and 1 plug, besides, it's cheaper than replacing 1 the coil, 2 the distributer, 3 timing chain and gears, 4 all injectors, OK so my local Jeep dealer wanted the money for all these parts. Start with your Crank Position Sensor.:confused1
 
90woodyxj said:
whoever designed the electrical on 88-90 jeeps should be shot
Click to expand...
A classic example of Ad Hoc engineering. I grew up working on the early CJ's, then the FSJ's, then the YJ and XJ. It's almost like they used the same basic harness for most everything and just added wires over the years (and sometimes parralell harnesses) as needed for new accesorries (the YJ harness and the Renix XJ harness share a lot). Dodge engineered in almost the same way. They'd use almost the same harness for decades, in many different models.
I was always amazed it worked as well as it did, most times. And nobody managed to wire a serious loop or some other boondoggle into it, during the next series revamp. Especially in the 91 models, when they added a new engine control harness and a tempermental engine control management system. I'm amazed it works as well as it does.
The first *major* change I can remember was in 97 or 98.
 
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