XJ40 ( XJ81 ) 1986 - 1994

ignition coil question

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  #1  
Old 07-06-2021, 06:11 PM
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Default ignition coil question

92 sovereign with 150k miles

No start the other day which I traced down to the ignition coil. Went ahead and got the cap, rotor, plugs and wires along with it since it had been a while (cps is also relatively new). The car fired right up and ran well for a couple days then started missing. I opened the hood and the the coil was sparking from the high tension wire at the coil from the cap. I checked it and the haynes manual I have says the primary should be .4 to .5 and the secondary at 6 to 6.5 k-ohms at 68 degrees F. The coil showed 1.2 on the primary and zero on the secondary. I took it back and replaced it but the new coil is showing .8 on the primary and 9.3 k-ohms on the secondary.
The temps here right now are around 88 degrees F and I'm not sure what that does to the expected values but I feel like these coils are not within the specs even with the temp difference. Any thoughts?

If it matters, I bought the coil from autozone since I was in a pinch and needed the car for the 4th - couldn't wait to order one
 
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Old 07-07-2021, 09:51 AM
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I'm still concerned about the resistance values versus what the book says but it seems to have calmed down. I think the insulator on the secondary wire was vibrating loose while driving and then settling down once it was parked in the driveway. I couldn't really see it well at first but I ran it last night so it was dark when I got back and the spark was definitely jumping to that lower post. I secured the insulation and all seems good again.
 
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Old 07-07-2021, 03:20 PM
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I made sure all of the insulation on the wiring at the coil was in place and just drove the car. The same thing is happening where the engine is missing and it wants to stall. There is a spark coming from the high tension wire on the coil but I can't really see it jumping to one of the posts which are insulated. Any thoughts?
 
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Old 07-08-2021, 03:19 AM
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Have you tried at night ? It's easier to inscpect high tension cables in dark area.
 
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Old 07-08-2021, 05:33 AM
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Yes I checked it at night and the spark is clearly coming out the high tension wire at the coil.
 
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Old 07-08-2021, 05:42 AM
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I think you have to change your cable.
Same as in my jag :

 
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Old 07-08-2021, 12:58 PM
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On my last local call, I found a Lucas coil. Put it in this morning and the car ran great and about twice a long as the other coil before starting to miss again.

Got it home and while in park and reverse, it didn’t do anything - all was normal. When I put it in drive, I’m getting sparks from the coil high tension output to both the positive and negative terminals on the coil. I secured the insulation on both of these after installing the coil thinking that the initial problem was they would vibrate loose and allow the spark to travel to one or both terminals.

I'll pick up another wire to make sure that's not the problem.

 
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