Hello all, I'm new, so thanks for all the help i know ill get!

So im running a 90 cherokee laredo, 4.0 I6. Now here comes the mystery part-

The other day as im driving home in the lovely 5:30 traffic, mr. jeep decides to shut off. It wasn't rough or anything, it was simply driving along 60mph about 2kish revs, and all of a sudden the motor just dies. It popped right back for a minute, but then died again. after that, i called both AAA and my friend, we tried jumping it back to life, but it would just crank...crank...crank...crank...but no turnover.

Now I have spent three days diagnosing, and reading on this forum. I have replaced the CPS, new distrib, even new relays. Tested all my wires and they showed to be good (coil to dist, dist to plugs; all were good). So we were stumped, and pulled a plug and one by one checked if the distributor would spark- no it wouldnt.
we checked if the coil would spark-nope.
so we tested the harness/connector (whatever it is) that the coil sits on, and it was getting current. so we determined it was the coil.

The question is, 1) is there another way i can make super sure it is the coil and not some mistake we made in testing?
2) I got a new coil a few days ago and tried it, but it made no difference-still wouldnt turn over but would crank.

Any help on this is beyond appreciated-this is currently my only vehicle, so its super important to get it fixed!

thanks for reading/helping

 

I can't be 100% sure but you may have the problem I was having. If so what I did to fix it was replace my tps and map sensor(actually I replaced all the sensors in the t-body) here's the issues I was having with my jeep. I'd be driving and once I accelerate it would stall in about 2nd gear. Then die, and from then on I'd stall and die all the time. When the check engine light came on it said it was a map, so I replaced it...2x, no luck. Then got a mechanic to give me the wire diagram and said good luck hunting. Lol after getting half way through I found out the tps connects to the map and gave it a false reading. Long story short, if yours is giving you this problem that info may help

 

Ground short maybe? You have already mentioned the likely issues.

 

Ive checked most of the wires i can see, and all of them seem to be ok, its raining right now so its a little iffy on getting good connections with the meter right now (no shelter to work under)

I'll check the tps, is there a way i could test it though to see if its getting a signal or not?

just as a side note- all my gauges read fine, and usually after i crank and crank it ends up having a dead battery (go figure) so maybe its shorting somewhere and its causing it to die so fast? Like we left it sitting for maybe an hour after we had tired jumping it (since i didnt get TDC when i put the new distrib in and were testing the spot it needed to be in) but once we came back like an our later it was absolutely dead, as in no crank just clicking...maybe something is shorting?

 

After reading that last part I doubt it's the tps, that is what happened while driving. However it only occasionally did a bad start up. From what you post above your saying you can't get it to start, and when you jump it you can't get it to charge? If so it may be an alt problem

 

Wait, back the truck up... you actually replaced the distributor? Wasn't that kind of expensive? Was there something physically wrong with the old one? And are you sure it's indexed properly now? Do you have fuel pressure? Could it be out of gas or maybe a bad fuel pump? Is your ASD relay connecting as it should (which provides power to the coil and fuel pump)? There are a host of things it could be, lets try diagnoseing the problem befor we throw any more parts at it. There is a way to jumper the ASD relay over to get power to things. Sometimes when you just start replacing parts with out testing first you can cause more problems than you orginally had. Take your time, think it through.

 

How about the fuel system? Did you check fuel pump/fuel pressure??

 

Ok, Ill answer those first,

Yes something was physically wrong with the last distrib, one of the wires (when i disconnected it to check) was missing, or atleast the lead of it was missing. and it wasnt too bad at all, only 48 bucks (reman. ftw)

Yes I have pressure, the pump is going, and i tested the contacts that the coil sits on, they are getting about 11.93 vdc, so i know power is good through there. but once i put the coil on and put a spark plug directly off the coil wire, the plug does not spark. Now this is true that i have not synced the distrib yet, but even regardless of that i should still get a spark off the plug, or atleast i would logically assume so...

and about jumping it, what i meant to say was that since I've been testing for spark (just cranking the motor) its run the battery low, so ive been jumping it a few times to get it to crank. the alt. is fine, tested it, got a strong voltage out.

 

when testing for spark at the plug, are you grounding the plug?

 

Yes

 

Test your new CPS. We've seen many of them bad right out of the box.

Renix CPS Testing and Adjusting
　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　
Revised 11-29-2011

 

Cps is reading fine

 

I would suggest checking the ignition switch. they can get dirty brass contacts, and the older the car the worse the wear. They especially wear faster if your key ring is heavy. This can cause early wear.
As you are cranking the engine tryplaying with the switch, moving the key back and forward some. You might need another person activating the starter by shorting across the solenoid.
Hope this helps.
Tom

 

Thanks tom,
Can you give me an idea of how exactly to short the solenoid? I have no idea where/how to do this

 

Update:
So far (and after much guessing, testing etc) I've come to the conclusion that the wires coming out of the relay block have gotta be grounded somewhere, came to this conclusion by
a) ICM and coil get power, took a test lead straight from the - batt to the coil->spark plug, got a spark, so the coil is good. the ICM is good, had it tested.
So time to go play pick a wire in that lovely little mess...im trying to think how to test which lead may be the bad one though? I know the people who designed this jeep (bless them...) decided to have the bundle of 35-40 wires run in conduit right behind the motor...so maybe one of them just gave up the ghost finally...so today I will be testing those out and looking around for anything else thats wrong...