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Will not start, no spark

Tiny
T-BON.605
  • MEMBER
  • 1991 JEEP CHEROKEE
  • 4.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Vehicle listed above is a Cherokee. Cranks but won't start. Spark on #1 and #2 cylinders only. Good fuel pressure. Replaced the Crankshaft position sensor, coil and the distributor pickup (camshaft) senor in the distributor. Cleaned the grounds. What am I missing? Any help would be appreciated, I'm pointing my finger at the PCM, but usually when I head down that road I'm wrong.
Thanks
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Saturday, February 20th, 2021 AT 5:01 PM

9 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
The fact that it is delivering spark to only 2 cylinders points to either the ignition control module or the distributor itself. I would remove one of the wires that is not getting spark and hold it close to the cap when you crank the engine. If there is not spark (safe to assume it is not) then I would put a distributor in it.

I attached the process below to do this. Let us know if you have questions.
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Monday, February 22nd, 2021 AT 3:34 PM
Tiny
T-BON.605
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  • 5 POSTS
Thank you for the reply. I would like to know why you are recommending replacing the distributor? I replaced the cam sensor/distributor pickup, in the distributor.
Would you please educate me here? I would like to understand.
Thank you
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Friday, February 26th, 2021 AT 9:25 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
When you say you are only getting spark delivered to only 2 cylinders, that points to the distributor itself. Specifically the cap and rotor as this is what spins and sends the spark to each plug wire.

I have seen many times where the distributor shaft/housing bearings are worn out and it causes the rotor to walk and the gap gets too large and it doesn't deliver the spark. Normally it will cause the rotor to hit the cap and it will break but not all the time.

If you have not replace the cap and rotor, I guess you can start with this but if you have or that doesn't solve it, I would replace the distributor.
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Friday, February 26th, 2021 AT 6:57 PM
Tiny
T-BON.605
  • MEMBER
  • 5 POSTS
Well, I replaced the distributor with a new one, cap and rotor too, I still have the same problem. So, I replaced the PCM and that did nothing to solve the problem.
So far I have replaced the cam sensor in the distributor, the coil, the crankshaft sensor, the distributor with another new cam sensor in it, cap, rotor, PCM, cleaned the grounds, took apart electrical connectors and made sure they looked clean and not corroded. The rotor does turn when cranking, the engine sounds like it has compression while cranking, although I haven't checked compression, it sounds normal though.
I still only have spark on number 4 and 1, originally I told you I thought it was 1 and 2. When I check for spark right off the coil I don't get a steady spark like I should for all 6 cylinders, I get: spark, spark, nothing, nothing, nothing, nothing; then repeats.
I'm stumped.
It was running fine, I shut it off one evening and the next morning it won't start.
What do I do next, any ideas?
Thanks
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Thursday, March 11th, 2021 AT 3:30 PM
Tiny
KASEKENNY
  • MECHANIC
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What brand crank sensor did you use? Was it a Mopar sensor or at least a Standard Auto brand? If not, we may have a bad sensor. Also, remove the sensor and turn the engine over by hand and make sure you are not missing teeth or any are cracked. I would have someone put a socket on the crank pulley bolt and spin it over as you watch in the hole for the sensor.
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Friday, March 12th, 2021 AT 5:53 PM
Tiny
T-BON.605
  • MEMBER
  • 5 POSTS
It was from NAPA, Echlin brand, I've had better luck with their stuff than any others. Also, I called a Jeep dealer and they were actually trying to be helpful. They asked if the tach moved while I was cranking it, as the tach gets its signal from the crank position sensor. Does this sound right to you?
I tried this and the tach doesn't move. So, I would have to assume that the new sensor is bad.
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Friday, March 12th, 2021 AT 8:42 PM
Tiny
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  • MECHANIC
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That is exactly what I was going to ask next. This is correct. The crank sensor gives the engine speed so if the tachometer is not moving then that is a sign that the sensor is the issue.
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Saturday, March 13th, 2021 AT 5:40 PM
Tiny
T-BON.605
  • MEMBER
  • 5 POSTS
Well, after much time and banging my head against the wall. It was the new Echlin/NAPA crankshaft position sensor that was faulty (faulty new part). Thanks so much for your help, I'm so glad to have it running again.
I had NAPA warranty it and the new Echlin part did work. I tried to get an OEM, but they now longer offer it, so aftermarket is the only choice.
Again, Thank you, Shawn
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Thursday, April 1st, 2021 AT 10:26 AM
Tiny
KASEKENNY
  • MECHANIC
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That is great info. I actually have another vehicle that appears to be the exact same thing where a new part appears to be faulty. That is the worst because you don't assume that it is so you move on. So glad you fixed this and even more that you updated us as that will help others in the future.

Thanks for using 2CarPros.
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Friday, April 2nd, 2021 AT 4:52 PM

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