Hi guys,

New to the forum and I have to say its been a life saver... but I'm running into a problem with crank no start no spark that is driving me insane.... I have a 90 Cherokee with the following symptoms:

CPS - New good .5vac and 235 ohms - Traced wires to ECM with .5 vac
ICM - Tested good at Autozone
Coil - Ohmed out good and swapped with known good
Rotor/Cap - New
Distributor - New purchase today (AutoZone)

All changes resulted in no change - still no spark.

Before I started replacing parts I did a ground and sensor refresh with contact cleaner and gleaming grounds... all ohm out to zero ohms.

At this point it looks like it may be the ECM but I HATE to throw more parts at this thing and am beyond fustrated.... this is a two week effort and no closer to finding out what the problem is.

I'm seriously outta ideas and ready to burn this bastard.... HELP PLEASE

What "ground refreshing" did you do?

Do It Man...Do It!

Take a vid.

Had a dent in a gas tank once ( 81' Honda cb1000 ) after empting most of the gas I ligh it up big boom and the dent was smaller, so put a little bit of gas in it again and it poped out the dent.
So who knows maybe you should throw the match in the tank and see if that will fix it up

At your own risk of course

Not worth the helicopter trip to the burn ward, or ride to the morgue. JMHO

Please step away from the gas can! .... I have a way to test your coil/icm together in your jeep. I've done this with my Renix. You need a voltage source close to 5volts. I used a free harbor freight flashlight. Pulled the AAA 3 pack out and taped a wire on each end. The - goes to chassy ground and the + is what triggers the spark. The icm has two plugs. A 3 wire plug and a 2 wire plug with just a yellow wire coming out of it. Pull the 2 wire plug and with a grounded spark plug in the end of your coil wire and key on, touch the battery pack + wire to where the single yellow went to the icm. The plug will spark every time you touch the 5v wire to the terminal unless there is a problem with coil/icm/wires to power and ground icm/coil. This helped me diagnos my no-spark.

OK... I got a wild idea to jumper +B Latch relay it starts for about 2 sec. then stalls... i replace the jumper with a new relay and no start... Now I'm assuming this is the Latch relay (2nd from the firewall) because I don't see a bad fuel relay creating a no spark.

This is strange beyond words... as for ground rehresh... i pulled all the grounds on the block, dipstick and put new crimped lugs on anything I though might remotely be sketchy since I was already working on it..

This makes no sense

Thanks for any help

Here.

Yes it is the latch relay.... I bypassed the fuel pump resistor earlier but no luck.

Yes it is the latch relay.... I bypassed the fuel pump resistor earlier but no luck. I'm beginning to think its the ECM because I took it apart and it smells burnt. No obvious signs of blown caps or anything but that's all I have left here.

Thoughts????

Try this first.



Cruiser’s Renix ECU Connector Refreshing

Many times when other fixes have failed, it becomes necessary to eliminate the ECU to harness connections as a cause. This requires removing the ECU.
Up under the dash, to the right of the steering column is the ECU. It is held in by three 10mm headed bolts to a bracket. It’s most easily removed using a ratcheting wrench but a socket will work.
Once you get the ECU down, unplug the two harness connectors from it. Visually inspect the connectors and pins.
Using a good quality electronics cleaner, liberally spray both of the harness ends and the ECU pin area.
Now, take a small pick or a dental tool and go to the harness connectors. Using the tool, tweak each female receptacle in the harness plugs so they will grasp the ECU pins more tightly.
Plug the harnesses back on to the ECU and reinstall it. I usually only use two of the bolts because the third is a bear.

Revised 07/11/12