89 xj has no spark! power to coil and CPS is good!

Hi My name is Justin and I need your help! I just got myself a '89 Jeep Cherokee limited with a 4.0 and 4-speed auto. The thing starts and runs great for a day, then as i go to lunch a couple hours later; it cranks but doesn't run. I check for fuel and spark. I got fuel but no spark coming from the coil. I checked the forums for hours, but people say the same thing, CPS or Coil. I checked the CPS resistance, it was within specs. I also checked the CPS with a scope and it reads a good signal, but i replace it anyways against my instinct. It still does the same thing. :dunno:

I checked the Power and ground to the coil, good... I checked the voltage to the CPS from the harness, good.... I checked the relays next to the coil and swaped them around nothing changed.

IMPORTANT! on a side note: The relays on next to the passenger side shock tower(near the coil) go crazy, on and off rapidly, when the key is in the run position! I never noticed this before. I have heard this problem mentioned before, but no one could effectively solve the problem.

Can anyone tell me what would cause my car not to run caused by no spark? I am stumped at this point and need help!
anything besides CPS please!!!1

almost anything helps!:dunno:Thank you

look at you starter relay (since theyre making noise), pull your ac relay and put it in there and see what happens.

~sm

the starter relay is a definite possibility, but its an 89, so it renix. what that means is the you can easily find the manual on the internet and check every conceivable thing out with the manual and a digital volt meter. the other thing it means is that you have to go through the whole engine wiring harnss and make sure every connection is clean, use an appropriate corrosion protection/ contact enhancer.
and if you have the dreaded c1o1 get rid of it. once that is done it will be he most reliable vehicle you have owned.

think 89 was the change year for the C101... 88 and back have them...

there are plenty of no start threads here, with varying results from varying problems.

I already switched the relays around...]
and I searched for hours on this forum, but couldn't find anything with the same problem i am having that had a fix.

relays swithing off and on... that is one possible clue...

what controls them? ECU ? U may have to dig deep in wiring diagram.

can you tell 'which' relay is cycling?

the starter relay has outputs to the ECU, Fuel pump ballast resistor, and to starter solenoid...
it is not one of the DIN square relays, but has the + terminal from the battery connected and if standing at the passenger wheel, to the right of the DIN relays. it is not swappable with the DIN relays.

from the starter relay, to the left is then the O2 heater relay, fuel pump relay, "latch" relay, then the A/C relay. these DIN relays are swappable.

good luck.

I applied power with my power probe to the ignition part of the relay with the key in the on position and bingo! :eyes: SHE IS ALIVE!!!!!:skull2:

So I ordered a new starter relay from Napa auto parts. :tears: I'm so happy!

Thanks but i don't think this is over just yet! I lost fuel pressure on the way home and i had to play with the same relay again, but the terminal that powers the fuel pump on start up. This may help some people that have good coils, CPS's and ignition modules but no spark or signal to the ignition module.

I am having the same problem what exactly did you jump?

I would check the fuse box for loose connections. I had to bypass my fuse box and rewire some of my lines with new inline fuse holders on my 85 and 87 jeeps in the last few years.

One strong possibility is the ignition switch on the steering column may be going bad in the run possition. Both went bad on my jeeps since I bought them just a few years ago, and one of the new ones got fried in only a year. Also the wiring harness connector and electrical terminals were damaged. Took some creative work to repair it all.

Also you may still have relay problems. Only time I had relays act up so far was when the O2 sensor harness fried itself on the exhaust manifold grounding out the 12 volt heater wire and draining the hell out of the entire 12 volt system power (battery gauge droped to less than 8 volts) till the fuse link started smoking. As I recall it fried a relay in the process.

Lastly, as I recall the starter relay on the fender near the battery also controls power to more than just the starter in the start mode, so when it goes bad it kills several things all at once even in the run mode.

ok i had this same problem with my 94 xj with the 88 engine i just put in it, near the transmission filling tube there are three ground wires that should be bolted to the block, make sure they are tight and theres a clean ground, it there is you should be getting a spark now, if you arnt check the voltage to the wire that feeds your coil, you should get 6 volts, if you dont have have an ecu problem or a short somewheres, if you do plug in the coil and check the voltage on the output of the coil, it should be 6 volts again, if you get nothing you need a new coil, if you get 6 volts out of that and still no spark check your cap, one of those should solve your problem, check everything i told you to then come back here and let me know the status,

edit:didnt read your post from before, check the ground on those three wires, that could be a culpret that will show its face