96 jeep cherokee crankshaft position sensor

brockjeep · 06-01-2009, 06:33 PM

My jeep turns over but absolutely refuses to start. All accesories work but I'm getting no spark to my ignition coil and was told it could be the cps. wondering if that is true; and i'm having a hard time locating it where my haynes manual says it should be (on the trans. bellhousing). any help would be greatly appreciated! (already changed dist. cap, rotor, pick up coil, and ignition coil; plugs :& wires, fuses, relays, and battery are all good)

**octaneman** · 06-01-2009, 07:19 PM

Hi brockjeep

Have tested the ignition module ? There are 2 types

**mack1** · 06-01-2009, 07:42 PM

Hi brockjeep and welcome to TSF,

How did you check for no spark? (sparkplug laying on the block with a plug wire connected to it?) Look for a strong blue spark. A weak redish spark will sometimes not fire the cylinders and it might be thought there was no spark.

Does the engine turn over strongly, or draggy? Note that when the starter is engaged, there must be over 9 volts at the battery terminals in order to get spark. If the starter pulls it down below 10, you'll probably get no spark. If you have a volt meter, check the battery voltage during start.

If you have electrical prints of the ignition system, you might post it here and we can help you troubleshoot the problem.

Very best regards,
Mack1

brockjeep · 06-02-2009, 06:00 AM

called pep boys and then jeep dealer, neither had an ignition module listed for my year/engine. '96 straight six should definitely have one? thanks

brockjeep · 06-02-2009, 06:11 AM

checked for spark with volt meter and the old screwdriver test, had a buddy check everything with meter, he was stumped, had a mechanic take a quick free look and confirmed no spark to ignition coil, low power to pickup coil, and then suggested the CPS. engine turns over strongly, sounds normal to me. I'll try to get the elec. prints posted later today. thank you Mack1

brockjeep · 06-02-2009, 05:50 PM

I've attached a scan of the ignition system diagram from my haynes manual, hopefully it's ledgable.

**mack1** · 06-02-2009, 09:34 PM

Hi Brock,

I was able to read the PDF file, but the definition was not good enough for me to mark it up and feed back to you. Would you mind scanning it again, save it if JPG format and repost. Needs to be less than 1.9 meg size for pasting to the post. That would make it clear enough that I could mark it up and send it back as a talking reference.

Without being able to feedback a marked up copy of the print, maybe I can give you something to check using words with you refering to your print. From the ECU, there is a dark green with red striped wire that goes to the injectors, alternator, and the ignition coil. I'm thinking that wire is normally high (probably 12 volts, but could be 5) and is pulled low each time a firing point is reached as the engine turns over. The coil circuit is very simplistic on that print and more data on the coil circuit would be nice. In any event, a measurement there might tell you if the ECU is telling the coil to fire. You can either unplug the wire at the coil for measurements, or back probe it. You should get a reading on the AC scale of you voltmeter with the engine turning over. Measure it first on the DC scale with the ignition in the run position. This will tell you if it is a normally high circuit that is pulled low by the ECU. If you get an AC voltage when the engine is turning over, then you will know that the ECM is trying to cause spark.

See if you have AC there and post back if not.

Best regards,
Mack1

06-01-2009, 06:33 PM	#1 (permalink)
brockjeep Registered User Join Date: Jun 2009 Posts: 4 OS: xp sp2	96 jeep cherokee crankshaft position sensor My jeep turns over but absolutely refuses to start. All accesories work but I'm getting no spark to my ignition coil and was told it could be the cps. wondering if that is true; and i'm having a hard time locating it where my haynes manual says it should be (on the trans. bellhousing). any help would be greatly appreciated! (already changed dist. cap, rotor, pick up coil, and ignition coil; plugs :& wires, fuses, relays, and battery are all good) Last edited by brockjeep; 06-01-2009 at 06:57 PM.

06-01-2009, 07:42 PM	#3 (permalink)
mack1 TSF Articles Team Join Date: Nov 2007 Location: Texarkana, Texas Posts: 1,245 OS: xp sp3 My System	Re: 96 jeep cherokee crankshaft position sensor Hi brockjeep and welcome to TSF, How did you check for no spark? (sparkplug laying on the block with a plug wire connected to it?) Look for a strong blue spark. A weak redish spark will sometimes not fire the cylinders and it might be thought there was no spark. Does the engine turn over strongly, or draggy? Note that when the starter is engaged, there must be over 9 volts at the battery terminals in order to get spark. If the starter pulls it down below 10, you'll probably get no spark. If you have a volt meter, check the battery voltage during start. If you have electrical prints of the ignition system, you might post it here and we can help you troubleshoot the problem. Very best regards, Mack1 __________________ "If you like yourself others will like you also" me "Don't drink downstream from the herd" Will Rogers Submit New Articles Here

06-02-2009, 06:00 AM	#4 (permalink)
brockjeep Registered User Join Date: Jun 2009 Posts: 4 OS: xp sp2	Re: 96 jeep cherokee crankshaft position sensor called pep boys and then jeep dealer, neither had an ignition module listed for my year/engine. '96 straight six should definitely have one? thanks Last edited by brockjeep; 06-02-2009 at 06:18 AM.

06-02-2009, 06:11 AM	#5 (permalink)
brockjeep Registered User Join Date: Jun 2009 Posts: 4 OS: xp sp2	Re: 96 jeep cherokee crankshaft position sensor checked for spark with volt meter and the old screwdriver test, had a buddy check everything with meter, he was stumped, had a mechanic take a quick free look and confirmed no spark to ignition coil, low power to pickup coil, and then suggested the CPS. engine turns over strongly, sounds normal to me. I'll try to get the elec. prints posted later today. thank you Mack1

06-02-2009, 09:34 PM	#7 (permalink)
mack1 TSF Articles Team Join Date: Nov 2007 Location: Texarkana, Texas Posts: 1,245 OS: xp sp3 My System	Re: 96 jeep cherokee crankshaft position sensor Hi Brock, I was able to read the PDF file, but the definition was not good enough for me to mark it up and feed back to you. Would you mind scanning it again, save it if JPG format and repost. Needs to be less than 1.9 meg size for pasting to the post. That would make it clear enough that I could mark it up and send it back as a talking reference. Without being able to feedback a marked up copy of the print, maybe I can give you something to check using words with you refering to your print. From the ECU, there is a dark green with red striped wire that goes to the injectors, alternator, and the ignition coil. I'm thinking that wire is normally high (probably 12 volts, but could be 5) and is pulled low each time a firing point is reached as the engine turns over. The coil circuit is very simplistic on that print and more data on the coil circuit would be nice. In any event, a measurement there might tell you if the ECU is telling the coil to fire. You can either unplug the wire at the coil for measurements, or back probe it. You should get a reading on the AC scale of you voltmeter with the engine turning over. Measure it first on the DC scale with the ignition in the run position. This will tell you if it is a normally high circuit that is pulled low by the ECU. If you get an AC voltage when the engine is turning over, then you will know that the ECM is trying to cause spark. See if you have AC there and post back if not. Best regards, Mack1 __________________ "If you like yourself others will like you also" me "Don't drink downstream from the herd" Will Rogers Submit New Articles Here