DieselD

So I’m at my father in laws funeral, I go to leave, Jeep starts and then sputters after a couple feet and dies. Cranked but wouldn’t start.

I had a buddy pull me home later on. I checked fuses and relays and ended up getting a bad reading on the crankshaft sensor, also was throwing a code p0113 intake air temperature high input.

So I got a new cps and put that in and still cranks but no start. I started checking the ignition closer, the spark is weak all the way back to the coil.

I tested the wires coming into the ignition coil. When I turn the key forward I get power to one, but the other doesn’t give an intermittent power at all when I crank it. Which I guess is the signal from the PCM (ecu?) telling the coil to fire.

I tested the the cps for power and it’s getting it, I’m about to have a multi meter brought to me so I can test more.

just looking for some help though 🙂

If cps checks out what do I do next? How/where do I start testing the ecm (pcm? Ecu?) lol

I have fuel btw.

Thanks in advance 👍🏼

BlueRidgeMark

There are tons of reports of aftermarket CPS being bad out of the box, or failing within a few days or weeks or months. Sensors on these beasties are picky. Save money and frustrations, bite the bullet and pay the dealer's price for sensors. However, if you have any spark at all, it's probably not the CPS.

Same is true of your ASD relay.

Weak spark is mostly likely your coil itself. OR the wiring going to it. Grounds are always suspect. That's why my #1 item in my sig is the #1 item in my sig. Poor grounds can do amazing things, but never in a good way!

DieselD

Thanks.

Yea I’m definitely getting spark and it’s definitely weak. I recently put an alternator on and everything ran fine after.

I’m finishing checking all the fuses inside because I didn’t before.

I am going to start refreshing grounds after that.

DieselD

Refreshed all the grounds. Still cranks but doesn’t start.

BlueRidgeMark

One thing to clarify - the PCM provides ground when it wants to fire the coil. Power is always there. Or at least, it's supposed to be!

I'd say the coil is your best bet at this point.

One more thing I would try: Using a test light, put the probe of the test light to the coil 12v supply, and the other end of the test light to the ground coming from the PCM. (Er t'other way around. Don't matter). Then crank and see if you get a good pulsing light from the test light.

DieselD

thanks for the clarification, I’ve read so much on the internet my head hurts, so there’s a chance I misread or was reading something for a different vehicle. I will probably stick a pin in it for now and maybe try replacing the coil tomorrow.

DieselD

Swapped a new coil pack in, same thing cranks and cranks but won’t start.

DieselD

Okay.

So I went to try it one last time before I called it a day.

it cracked but sounded like it was trying to fire, so I feathered the throttle and it fired up and ran.

However it started to run rough. It stabled back out and threw a p1391 code.

I think the cheap CPS I put on there is bad.

I took it it for a drive and it kept misfiring and running rough bogging down, etc. I will probably swap back in the old CPS tomorrow.

BlueRidgeMark

Could very well be. On these beasts, sensors are touchy, especially the CPS. You just have to bite the bullet and pay the dealer's price. I just popped $186 for one for my WJ. Ouch.

I don't remember, but did you check out the Cam Sensor? It's also involved in the spark.

BillyBoy

Try cranking it while wiggling wires and harnesses. The main harness going across the top of the engine bay especially. I had the same issues as yours and couldn't find the culprit. Those wires are heated and cooled and are prone to weakening. Crank while wiggling... it works.