• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Start no start issue 88 Cherokee......

B.RAIDER

NAXJA Forum User
Location
Central Texas
1988 Jeep Cherokee 4.0, I6, Auto Trans, 4X4
Trying to diagnose a no start problem.
All grounds are good and battery is strong.......

At times the Jeep will start and run fine for about 5 mins or so then shut down.
After a bit it will restart.....sometimes 10 to 15 mins....sometimes not for hours.
I have determined that it is not a fuel problem by testing the fuel pressure with a gauge at the fuel rail. Also Have new fuel filter installed.
Also the CPS at the flywheel is new. It also checks out good by ohming it (222 ohms).

When it shuts off …… I have no spark from the coil.
I do have power at the ignition wire(12 volts) to the three wire ignition module plug….but no tach signal from the module plug when cranking (I checked these by probing while plug is connected).
I have also checked the pin at the D1 diagnostic connector….no tach signal there either when cranking.
Does this indicate that the ignition control module under the coil is bad?
Or could it be something else?
Is there something else I should check in conjunction with what I have checked so far?
There are a brazillion threads on this topic have read a bunch of em but have not yet found my answer.
Thanks ahead of time for any help................
 
Last edited:
Crank sensor to ECU to ICM to coil to distributor is the path.

Are the dipstick grounds (ICM, ECU, o2 sensor, and others) cleaned to bare metal, and good and tight? Yes, saw your note, but gotta ask!

Take the coil off the ICM, clean the contacts and treat them with dielectric grease, then reassemble.

You have power to the ICM/coil when symptomatic, so the B Latch relay is good.

If cleaning the contacts between the ICM/coil doesn't work I would pick up a ICM/coil at the salvage yard and see if that does it. If it doesn't, then grab an ECU.
 
Crank sensor to ECU to ICM to coil to distributor is the path.
You are talking about the CPS (crank sensor) at the bell housing, If I understand this statement.
Are the dipstick grounds (ICM, ECU, o2 sensor, and others) cleaned to bare metal, and good and tight? Yes, saw your note, but gotta ask!
I have cleaned all the grounds under the hood and all OHM out good at all three locations. I have done this chasing the high idle problem that I have not been able to remedy (1200-1500 rpm in park or neutral). The O2 sensor is new.
I have not removed the ECU yet as of this time to check connections there.
Take the coil off the ICM, clean the contacts and treat them with dielectric grease, then reassemble.
I did this….. but did not put the dielectric grease upon re-assembly.
If cleaning the contacts between the ICM/coil doesn't work I would pick up a ICM/coil at the salvage yard and see if that does it. If it doesn't, then grab an ECU.
They want 50 bucks just for the ICM at the PNP here. Leaning towards getting a new one for a hundred bucks, the coil itself is about 50 bucks new.... If can’t get passed trouble shooting it.....I'll go that route(new).
 
Last edited:
Damn, that is a little spendy for a salvage yard. I think my last ICM/coil was $20 here.
 
Damn, that is a little spendy for a salvage yard. I think my last ICM/coil was $20 here.
Yep it sure is........if it was that cost here....I'd go for it. No tellin what they'd ask for the ECM....but I'm gonna call later and find out. They only had 3 Cherokees yesterday when I called, an 85, a 88 and a 89.
 
While your at it, check the bulkhead connection. I had the exact same issues on my 88 and discovered that the bulkhead connector was the issue. I eliminated it, and have not had any starting issues since

A quick test to determine is the bulkhead connector is the issue:
1) next time the XJ wont start, visually verify that the tach isnt moving
2) open hood
3) take a screwdriver or hammer, and smack the connector on the bolt that holds it together. or shake the wire looms on both sides. hammer works the best though.
4) try to start XJ, if the tach starts bouncing the jeep will start

On occasion it would take a couple of try's to make this work. If you are successful eliminate the POS connector.
 
While your at it, check the bulkhead connection. I had the exact same issues on my 88 and discovered that the bulkhead connector was the issue. I eliminated it, and have not had any starting issues since
A quick test to determine is the bulkhead connector is the issue:
1) next time the XJ wont start, visually verify that the tach isnt moving
2) open hood
3) take a screwdriver or hammer, and smack the connector on the bolt that holds it together. or shake the wire looms on both sides. hammer works the best though.
4) try to start XJ, if the tach starts bouncing the jeep will start
On occasion it would take a couple of try's to make this work. If you are successful eliminate the POS connector.
I should have mentioned that I did clean the C-101 connector with a brush and contact cleaner and applied fresh dielectric grease. This was all in attempt to chase my high idle. I have unplugged it and plugged it back in several times just to see if it has made any difference…..so far no difference. It might need be completely removed from firewall and checked. But it was in pretty good shape looking at it from the engine bay when I cleaned it.
When you're puling your own parts at the JY and they fit in your pocket I just consider them part of the admission fee :)
Tempting…..but…..Not worth getting caught, embarrassment, jail time or whatever the consequences might be.
 
I had a similar issue a few years back, if your feeling froggy take the ECU out and open it up to see if any circuts are fryed or close to fried. I went through 3 ECU's.
 
The CPS is available from your local Jeep dealer. They have a direct replacement and a service update (Part #83100066.) I just replaced mine with the service update and my problems have resolved.

The difference in the two is simple, the service update includes a new harness with the two leads that you install through a new hole in the firewall and connect directly to the ECU, bypassing the original harness connections and leads.

The service doc is locatable using Google (http://www.google.com/search?q=jeep+reference+J007) (aka "Chrysler Service Bulletin 18-51-88")

Hope this helps...
 
The CPS is available from your local Jeep dealer. They have a direct replacement and a service update (Part #83100066.) I just replaced mine with the service update and my problems have resolved.

The difference in the two is simple, the service update includes a new harness with the two leads that you install through a new hole in the firewall and connect directly to the ECU, bypassing the original harness connections and leads.

The service doc is locatable using Google (http://www.google.com/search?q=jeep+reference+J007) (aka "Chrysler Service Bulletin 18-51-88")

Hope this helps...
Did they give you the parts to do the upgrade or was there a fee?
I have stated in my first post the the CPS checks out after being replaced with new.
 
Finally got back to tinkering with the rig this morn. It finally gave up the the ghost and wouldn't start at all, but I still had power to the ignition wire at the plug. Changed out the IGN module with one from the jy and it fired right up. In my opinion, it had to be a thermal breakdown in the ign module, not the coil itself.
So we'll see if that was the fix....but so far so good.
Thought I'd post up my findings in case others were chasing the same gemlins.
Now to tackle my idle problem.
 
When my CPS went out I replaced it with a new one that was defective from the factory (thermal failure) checked by pouring water on it to cool it and the engine kept running. Verified problem by heating it in the oven to 200 deg. and checking with an ohm meter.
 
A hairdryer also comees in handy to test for heat-related failures, and allows you to do it in situ.

@B.RAIDER - So, your ECU came up as "failed?" If you haven't gotten rid of it yet (please say you haven't!) I'd like to get it from you for my own research. Enclose a sheet with a brief description of the application and a description of the failure, so I've got an idea what I need to check for when I finally open it up (NB: This would be the first RENIX ECU I've heard of that hasn't had an injector failure - as far as that failure goes, I've heard of four and have been able to get two shipped to me...)

Figuring out RENIX has become a cross between "pet project" and "Holy Quest" for me. ACTIA Corp isn't terribly forthcoming with information, but I'm due to try again (as far as I can tell, they're the most recent patent holder for RENIX.)
 
B.RAIDER - So, your ECU came up as "failed?" If you haven't gotten rid of it yet (please say you haven't!) I'd like to get it from you for my own research. Enclose a sheet with a brief description of the application and a description of the failure, so I've got an idea what I need to check for when I finally open it up (NB: This would be the first RENIX ECU I've heard of that hasn't had an injector failure - as far as that failure goes, I've heard of four and have been able to get two shipped to me...)
My Electronic Control Unit (ECU) appears to be fine.....haven't messed with it yet.
It was the Ignition Control Module under the coil that I replaced.
I have had it running off and on all day and drove it a round a bit and it's still running OK (except for the 1500 rpm idle in park).
 
My Electronic Control Unit (ECU) appears to be fine.....haven't messed with it yet.
It was the Ignition Control Module under the coil that I replaced.
I have had it running off and on all day and drove it a round a bit and it's still running OK (except for the 1500 rpm idle in park).

Ah.

I may still be interested in that as well - I need to devise a reliable and simple ICM test that can be done easily, and I'll need a "guaranteed fail" to go along with all the "worked when pulled" bits I'll be devising on. Lemme know.
 
i have the same problem power to the coil but no spark...im going to check the ICM hope its it. Thanks for all the info.You gotta love naxja
 
Back
Top