Death of an XJ?

At the end of my rope. Currently, My 89 cherokee has a new:
In the past few months:
Clutch
Pressure Plate
slave cylinder
throw out bearing
set of Dueler Revo tires

And in keeping with the spirit of throwing good money after bad:
Crank Position Sensor
copper champion truck plugs
ground strap
Distributor
Cap
Rotor
ignition Module
ECM
Plugs
another CPS
ignition coil

the good news is that i am a Service Manager, and get great deals...
the bad news is that with 2 techs and myself looking at my jeep for 4 days or so... we still have an intermittent spark and intermittent injector pulses.

It kinda started with a clutch job. Job went well, clutch and motor mounts, transmission mount for my peugot piece of 5 speed, and it was great to drive!!!
then one night it started to stall the motor when i got more heavily into the gas. and then any increase in throttle at all (more like spark cutting out than fuel, in my opinion.
Then, on the way home sunday night, It cut out, and has been selective about when it starts since.
For a bit, it would only start with a spark tester in line with the coil/dist cap. Fun, huh?
We've tested continuity from nearly every sensor to the ECM, and found resistance to be good.
Coil, module, and internal distributor are all (now) doing what they should. (Dist. was killing power when plugged in on 1 wire... .4 volts where there should have been 5.)
Today, I pick-and-pulled an ECM from a donor 89 automatic. And i saw the spark tester come to life. for about 5 minutes.
no pulse at #3 injector, where the noid light was plugged in.
Tech went to spray some starter fluid into the intake, went to start again. No spark now.

Please, oh please, oh pretty please, someone put me or my Jeep out of my misery.

Otherwise, i'll have quite a few spare parts to go around, so i'll entertain those requests as well.
thanks all.
Sam

1989 Cherokee 2 door
4.0 Liter
5-Speed
4wd
197kmiles

Oh... yeah... I have also replaced the crap firewall to engine ground and tested the rest of the battery cabling and found resistance to be acceptable.
theres a new starter motor too (the old one liked to click sometimes in leu of starting) to start the begging for.

Have you checked and cleaned all of your grounds? The one at the rear of the head-to-firewall is most critical. EDIT, I see you have replaced this one! Check the 3 grounds at the dip stick tube hold down bolt.

Also have you cleaned the bulk head connector?

Do you have a RENIX service manual(for the fuel system only)?

Have you checked the SYNC sensor? Also is there any oil in the bottom of the distributor housing, this will shut it down.

bulk head connector... i expect you mean the mass junction on the firewall, yes??? I'll do both first thing tomorrow.
p.s. fuel pressure is steady, if i remember, 35 or 39.

makkman said:

bulk head connector... i expect you mean the mass junction on the firewall, yes??? I'll do both first thing tomorrow.
p.s. fuel pressure is steady, if i remember, 35 or 39.

Click to expand...

Yes, the one at the firewall, I would try remove and re-install just to make sure there is contact being made, this connector gets moisture and will corrode after time. Beware, there is a black tar looking stuff in there from the factory, this is normal.

The RENIX manual goes over all of the inputs and outputs that control the fuel and spark delivery. If you do not have one, PM me here and I will get back to you in the am.

I see you replaced the computer with another one, but this was exactly what happened with my 87 a few months back. Intermittant no spark. Finally figured out it was the computer and have not had any issue since after replacing it. I bought a reman from NAPA. If your wiring is like my Renix mess, there's a large bundle of unprotected wiring that runs along the passenger side fender. Years ago, I had a no start issue and found a sharp edge on the fender had wore through a few of those wires and they were grounding out.

Good call to check there too. thanks Gasman.
if it weren't for the freaking tires... i'd have just driven it to the junk yard when the clutch and motor mounts went out!!!

I believe what my tech, Eric, called those wires was "unholy mess". sounds about right, no?

And also check the underside of all your relay sockets for corrosion. See my pics below for what I mean.

It caused just enough 'cross talk' between the wires, that the relays intermitantly failed to work.

Also there is a major ground splice (see last pic) against the firewall behind the valve cover inside the wiring harness that feeds all the injectors and the ecm. Might want to check that too.


Before:



After:



The elusive Ground Splice:

have i ever mentioned here that i think an engineers hell is to become a technician???
Maybe with our powers combined, my jeep can once again be soemthing other than a paperweight!
thanks MapleDitch

if you have another known good battery lying around the shop toss it in there for grins and giggles.

What are symptoms of a worn timing chain? Not sure of renix setup, but how about the cam position sensor and distributor alignment? And it sounds like the 2nd ecm is making the situation worse, so I'd swap back in the 1st one with the sporadic starting.

Take a look at this- not sure how close your arrangement is to the later XJ's but this guy took awhile to find the reasons for a random sputtering and stall- http://www.accessmylibrary.com/coms2/summary_0286-31167993_ITM

Ok fellas, found it.
had one of the grounds at the pass side of engine block come loose.
turns out it's the 2 grounds from the PCM.
Yeah, that'll throw things all out of wack.
Thanks for the help!
Sam.
ug. next time, it's spare parts for all!

Those grounds will get you every time!

Glad you fixed it. Check your e-mail in about an hour for 100 pages of useful knowledge