I have a 1999 Cherokee sport four-wheel-drive with a 4.0 L engine. Driving to Oregon the engine died. Waited 20 minutes and she fired up. Drove a little and it died again. Ads it an autozone and started testing items. I replaced the crankcase sensor, coil (which was cracked), and nothing. Ended up towing back to california. I read many forums about this problem. So I started replacing parts. I now have new cap, rotor, plugs, wires, new distributor, new injectors, a Mopar crankcase sensor, all new relays, fuses, ignition switch, and pcm, cleaned all grounds, cleaned all power cables. Replaced starter before the trip. I think I replaced it all.
Now, I still have no spark to coil. It turns over but won’t start. Fuel compression test was good. Power to relays checks out. Power to pcm checks out. Any ideas would be greatly appreciated. I even replaced pigtails to injectors ( found one really bad one).

thanks
Jon

 

If you havent already, download the FSM, this can be done from Cruiser54 website

Go to the "Index"

Go to "Diagnostics, Ignition system"

Perform the procedures outlined

summary, you need to have 12V at coil, which is earthed by PCM, could be a bad connector or wire, if it isnt a component

 

Do you have any engine codes?

 

Considering my lack of experience with the coil-pack engines the first thing that pops into my head with a 4.0 no spark is the crankshaft position sensor.. Every time i have gotten an issue of no spark beyond the cap, button, or coil it has been the CPS...

Video on how to test it... If needed:

 

I ran for codes and have none showing. All fuses are intact and no melted wires I can see.

 

I replaced the crank sensor a total of three times (2 after market and last one Mopar)

 

This one stumps me fellas. Every test passes, every visual inspection looks good. Crazy. Taking to my Jeep only mechanic tomorrow, as I am not equipped with a hi-tech scanner. Maybe they can find something. Keep you posted.

 

did you free download the Factory Service Manual and perform the comprehensive tests outlined ?..no scanner needed

There is absolutely nothing more any technician could do to identify the fault than what it shows in there..in fact he will waste a lot of time if he doesnt have access to it

 

Did you test with a multimeter? Do all of the sensors have power? Are signals being received at the PCM? Did you test the integrity (resistance) of all the wires?

Since the CkPS is notorious for going bad w/o generating an error code, I would (have) started there.

 

don't overlook the camshaft sensor, it may throw the same code as a crankshaft sensor, basically does the same thing but the camshaft sensor is in the distributor, under the cap and rotor. it's the round plate under it that has the wire sticking out. first check to see if the plug is connected.
otherwise, i have no ideal. lol.

 

Hey guys,I did find the service manual online and downloaded it. I ran some diagnostics, via multimeter. However, it appears as though my multimeter as since quit. Time for a new tool (wife will be so happy). I have to wait a few days before I can get a chance to open the hood again. I will keep you guys posted. Thanks to all that have responded. It’s a big help getting others’ ideas.

 

itll run with a bad cam sensor, i may have written a book once upon a time, only to find that out.

Ide say confirm all grounds are 100%, also you said you had power at the pcm, do you have signal out?
is the pcm a matching serial number? new/used?

 

Should we get the Hantek out?

 

no regrets i learned tons of new things. never did test the spark wires lol.

cps is the only thing thats ever cut out while driving, hes got mopar though. my bad cam sensor was a newer mopar too though
.

 

Has anybody looked at the ASD relay?