MBGXJ

---Resolved---

Hello,


This is my first post. I've had my XJ since 2017. I have really enjoyed driving it and it's been good overall. All the issues I've had so far were relatively easy to fix until now.


Recently, I was driving and it died as if the ignition switch was turned off, no rough running or sputtering, no warning whatsoever. When I tried to restart it, the starter cranked hard, but it didn't even try to fire. The check engine light isn't staying on and I'm not pulling any codes. Even after diagnosis and several attempts to start, the battery is reading 12.4 volts, and the starter is still cranking with authority. So I don't think this is a battery issue.


Due to the way it died and the way that it doesn't even try to run, I am fairly certain I don't have any spark. I can hear the fuel pump running and I tried dumping a little gas down the throttle body, still nothing at all. The 2000 XJs have an all-in-one coil pack rail, so I'm not completely sure how to verify that I don't have spark, though I am highly confident that this is the problem.


I checked the CPS pigtail with the ignition turned on and it has 5 volts on the (number 3 pin?) the center pin is grounded and nothing on the signal pin. I tried two new CPS's, one cheap no-name part, the other was from Walker. That didn't help so I replaced the Cam Position Sensor, then the coil pack.


I believe that I either have bad wiring or a bad ECM. So the next step (should have done this sooner) is to verify the electrical input to the coil pack, but I haven't been able to find what each pin should be feeding to the coil with the ignition turned on. Does anybody know of a way to test the circuit going to the coil with a multimeter or how to test the ECM for that matter?


Is there anything else that could be preventing me from getting spark?


If I can't find a way to verify the coil circuitry, I would probably bring it to a shop, but I would hardly trust the local place to do an oil change and the next closest shop is nearly an hour away.


The vehicle is a 2000 Cherokee Sport with 4.0 an automatic transmission.


Thanks!

Ralph77

So the Jeep stopped running that time you posted about and you have not been able to start it since?

BlueRidgeMark

Welcome!


That's easy. Remove a spark plug, make sure it's solidly touching the engine block, and crank it. Look for spark at the spark plug gap. You can also buy a cheap spark plug tester. Makes the job easier, though I'm not sure how that works with a coil pack.


You won't see anything on the signal pin unless the engine is turning over. If there is no signal with the engine turning, there is your problem. Aftermarket CPSs are notorious for not working, or failing soon. If it's not Mopar (NGK/NTK), don't believe it's good.

Happens, but rarely. That's not where you should be going at this point.

ASD relay. Simple test (swap with one of the other relays), cheap fix. Look at that before you do anything else.

Dave51

Any OBD codes?

Dave51

Check Fuse 18 while you're at it.



Do you have a DVA option on/for your multimeter? May need that or the Hantek, but concur prob just the ASD.

MBGXJ

Thanks for the replies, everyone!

I found the problem. I am quite embarrassed to say that Dave51 had the right answer with fuse 18. I'm not sure how I missed it, because the first thing I did was check all the fuses (apparently poorly). I think because fuse 18 is labeled "fuel injectors, coil rail..." I may not have looked at it as closely as I should have. I guess this is a good lesson in being thorough during initial diagnostics. I could have saved myself a lot of time, money, and grief.

Anyway, I will run it for a while and see if it fails again. Are there any common problems that would cause that fuse to blow?

lawsoncl

Try wiggling and flexing the wiring harness that feeds the injectors where it crosses from the engine block to the firewall. Failing motor mounts can contribute to flexing and the wires can fatigue and break, or chaff and short out over time.