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no spark & no start issue for 6 months now

79yj

NAXJA Forum User
Location
Troy, IL
I have my XJ stored at a buddys place & during the winter he would go out and start it every now & then to make sure everything was good & charged etc.
One day he went out & it would crank & crank but not start.
Through a process of elimination I have replaced the CPS...the computer...the pickup coil....& the relays due to it not having spark and fuel either.

I have found that if I bypass the relay & make it give power the fuel pump does pump & the coil gets power......but it doesnt make spark at all.
I also noticed the coil has a crack around the bottum.

Just a simple question here.....when a coil has power & ground but doesnt produce spark does that automatically make it bad or does the distributer pull spark from it?
I plan to throw a coil on it but it would be nice to know it is for sure bad 1st.
Hopefully this is it.....I am tired of buying parts & doing no wheeling.

Thanks for any help you can offer.....I need it.
Eric
 
Have had close to the same problem. I would check the ignition module(attached to the bottom of the actual coil).
 
Not a relay issue at all....I have changed them all 2 times now.
There is no module under the coil. only a bracket and then the block.

Does anyone know how I can test the coil?

Thanks,
Eric
 
What year, your profile says 98 XJ, is that correct?

There is an electronic ignition control module (called the ICM) attached to the bottom of the HV coil. The PCM (ECU) computer grounds the HV coil input IIRC on the low voltage side, that causes the secondary coil field to colapse and fire the spark from the coil. A leaking HV spark can fry the ICM. THe CPS sends the timing signal to the PCM which modifies the timing signal and outputs the ground signal to the ICM.

Have you replaced the ignition switch yet? Might want to check the FSM or a Haynes manual wiring for the entire ignition circuit layout. I think the is a also an anti rolover switch that can shut down fuel and spark on the newer jeeps, and the cranking signal to the starter is independent of the ignition switch power to the PCM!!!
 
I dont see an ICM or anything on the bottum of the coil.
It was an early 98 production so maybe the 97 specs would be correct.

I pulled the coil totally out....bracket and all. I can gaurantee there is nothing under it but the engine block. So where would this ICM be located?...distributer is the only thing I see close.

Do they make a 1 wire hei conversion for this thing?

Thanks,
Eric
 
79yj said:
I dont see an ICM or anything on the bottum of the coil.
It was an early 98 production so maybe the 97 specs would be correct.

I pulled the coil totally out....bracket and all. I can gaurantee there is nothing under it but the engine block. So where would this ICM be located?...distributer is the only thing I see close.

Do they make a 1 wire hei conversion for this thing?

Thanks,
Eric

Yours may be a newer design. Does the coil assy come apart at all, or is it one cast piece? I thought mine was once piece until I took some screws out of the bottom or top and it turned into two halves, the bottom half was the ICM. Maybe by 97 the ICM was included in the main computer.

How about the ignition switch and rollover switch?

From what I have read the jeep ignition coils are extreemly good and rarely fail, but they do fail. I would stick with the OEM spark ignition set up. THose that have tried upgrades were not impressed. But the steering column ignition switch is another matter.
 
For sure it is one piece with a plug that goes into the side pos + neg . no bolts in the thing besides the ones I removed to get it off the block/bracket.
If it is in the computer then I have allready changed that out.

This thing has me stumped!

thanks
eric
 
Don't forget the ingition switch on the steering column. I have replaced 2 in one year on the same jeep!
 
I have the exact same problem in my 97 XJ. changed the coil, batt ends , CPS sensor, and still no start , just cranks and cranks. got fuel to the rail but no spark..????? let me know what you come up with. also my coil doesnt have the part they are talking about either. just the coil and a bracket that goes to the block.. let me know what you figure out.
 
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