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98 cherokee sport no spark

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Old Oct 10, 2014 | 08:10 PM
  #16  
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Alright gentlemen here is the latest. So parts replaced (all oem parts): plugs wires dizzy cap rotor ignition coil distributor ignition pickup and cps. Still no spark. Checked all fuses and qiring and nothing exposed or blown. Any ideas?
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Old Oct 10, 2014 | 09:25 PM
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Do you hear the fuel pump prime when you turn the key? If not, for kicks and giggles, try jumpering the Asd relay. It eliminates it as an issue, or shows its faulty.
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Old Oct 11, 2014 | 07:30 AM
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Originally Posted by perez1989
Check to see if your jeep has a pick up coil in the distributor. That also controls the spark on the ignition.
FYI: The manufacturer calls that a Switch Plate in the parts catalog. The FSM refers to it as a Camshaft Position Sensor (CMP).
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Old Oct 11, 2014 | 07:32 AM
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Originally Posted by old big red
Alright gentlemen here is the latest. So parts replaced (all oem parts): plugs wires dizzy cap rotor ignition coil distributor ignition pickup and cps. Still no spark. Checked all fuses and qiring and nothing exposed or blown. Any ideas?
Can you describe how you determined you are not getting spark please.

Did you perform the tests in my previous post?
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Old Oct 13, 2014 | 09:27 PM
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Originally Posted by CCKen
In the previous post wiring diagram, did you notice that the coil is engine gounded. That is, the coil itself is grounded to the engine.

When you replaced the coil did you make sure the surfaces of the coil, and the coil mount, are clean and capable of grounding to the engine?
Ok well here im going to state that very good point and I apologize for overlooking this comment. No I did not check that. Update though. So battery was bad and fuel pump relay is bad but asd relay is fine. Found a link on how to bypass those so I tried it and that's what I found. So tomorrow im going to check the coil grounding. But if it isn't grounding does that harmit at all?
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Old Oct 14, 2014 | 12:50 PM
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Well cleaned the bracket and made sure ignition coil was clean and still nothing.

Last edited by old big red; Oct 14, 2014 at 12:59 PM.
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Old Oct 14, 2014 | 01:10 PM
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See post #13.

You never did say how you determined that you are not getting spark, nor if you did the tests in post #13.
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Old Oct 14, 2014 | 01:39 PM
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Pulled out a plug hooked it back into boot grounded it out and no spark. Took wire off coil and cranked and no spark between coil and wire
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Old Oct 14, 2014 | 01:51 PM
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Originally Posted by old big red
Pulled out a plug hooked it back into boot grounded it out and no spark. Took wire off coil and cranked and no spark between coil and wire
You need to determine if you are getting 12 volts to the coil and if the PCM is pulsing it to ground.

If you don't have voltage and/or ground pulse there may be a PCM driver problem or voltage supply problem. That is to say that the ASD relay is functional.

Last edited by CCKen; Oct 14, 2014 at 01:59 PM.
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Old Oct 14, 2014 | 01:52 PM
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Asd relay is good. I jumpered it last night and vehicle acted the same. Trying to find volt meter at the moment to test all points.
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Old Oct 14, 2014 | 05:34 PM
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Ok gentlemen here ya go. So come to find out im only getting .12 volts to my ignition coil. Where do I go from here.

Last edited by old big red; Oct 14, 2014 at 05:42 PM.
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Old Oct 14, 2014 | 06:44 PM
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Originally Posted by old big red
Ok gentlemen here ya go. So come to find out im only getting .12 volts to my ignition coil. Where do I go from here.
Is that decimal point 12? Are you sure you have your meter set to 20 volts DC?
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Old Oct 14, 2014 | 07:08 PM
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Yes it is a decimal 12 and yes im positive. I have 3.8 coming out the pcm but a quarter that actually gets to my ignition coil. I tried to take a picture but the downloader wouldn't let me
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Old Oct 15, 2014 | 07:39 AM
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Originally Posted by old big red
Yes it is a decimal 12 and yes im positive. I have 3.8 coming out the pcm but a quarter that actually gets to my ignition coil. I tried to take a picture but the downloader wouldn't let me
How did you determine you have 3.8 volts coming out of the PCM?

I think you should get another Voltmeter (Digital) and check your voltages again. Sometimes a bad Voltmeter will send you off chasing your tail with bogus readings.

Edit: The 12 volt power source to the coil does not come from the PCM. It comes from the ASD relay via fuse F21 in the PDC.

The PCM provides the ground driver for the coil.

The wire carrying the 12 volt source is the Dark Green.Orange tracer wire at the coil. The PCM driver wire is the Gray wire.

Last edited by CCKen; Oct 15, 2014 at 07:52 AM.
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Old Oct 15, 2014 | 08:00 AM
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Volt meter is good. Even tested a few circuits on my wife's car and got exactly what it was supposed to be. So your telling me the dark green wire with the orange tracer coming from the pcm does not go to the coil. Tested it multiple times and every time it came back with the same reading

Last edited by old big red; Oct 15, 2014 at 08:37 AM.
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