Coil pack resistanace testing for Dummies?

[LibertyTC]

Could not find anything in the FSM? (hard to believe)
Did I "miss" something? :shrug:
Does anyone know the correct procedure for testing KJ coil pack ohm resistance testing?
What should the resistance be when removed from Jeep? How is this done?
Can you do a live/ turn the key on while connected VOM test as well?
My jeep has a slight miss my guess, (engine shake) no codes present.
Or is there any way in live data to find out what cylinder is being effected?

One could possibly say that all the coil pack ohm readings should be close and if one is out to Lunch , maybe that is the bad one? :mexsmoke:

 

[profdlp]

...One could possibly say that all the coil pack ohm readings should be close and if one is out to Lunch , maybe that is the bad one? :mexsmoke:

In the absence of a better plan, I'd say that sounds like a good place to start.

 

[CactusJacked]

Primary side resistance (jumping across the two electrical prongs), should be between .6 - .9 ohms.
Secondary side resistance (between either of those two prongs and the connector inside the boot) should be between 6,000 - 9,000 ohms.

 

[uss2defiant]

Checking the resistance involves 2 parts:

1. primary resistance
-measuring the resistance between the two pins in the ignition coil connector
primary resistance between 0.6-0.9 ohms

2. secondary resistance
-measuring the resistance between one of the connector pins to the spring inside
secondary resistance at 6k to 9k ohms

I wouldn't do a live test.

 

[LibertyTC]

Thanks Chuck & Brian, That is exactly what I needed to know.
How do guys know this? Was it somewhere in the FSM or over at lost or?

 

[uss2defiant]

I had a printout from autozone.

I also have a Hayne's manual.

 

[LibertyTC]

Huh...
Does Auto Zone test the coil pack & then give you a print out? (no autozone here)
I think I have a Hayne's 02-07 Liberty manual too somewhere.
Put it away years ago, since I have the digital FSM Version.
Never would have thought the Hayne's had the coil pack test in there.
Time to find the Hayne's book & start to use it as a secondary reference...
Thanks!! :waytogo:

 

[LibertyTC]

My next question that just came to mind is:
If one of the coil packs are out of spec, could it cause a slight misfire without tripping the engine light?
That would explain the slight engine shake and possible hesitation.

 

[CactusJacked]

I've had bad coils in the past, not the Jeep yet, but they always caused a cylinder misfire code. If one is bad enough to cause a rough running engine, I'd expect a code to be thrown. We'll see what your ohm test comes up with.

 

[uss2defiant]

Autozone does not test ignition coils.
I bought one from them as I had to wait for NAPA's coils to show up. NAPA's are OEM.
The associate printed out the service bulletin for it which was how to check the resistances of the ignition coils.

Also the resistant values are in the FSM under the ignition control section.

You probably need a successive amount of misfiring for the CEL to go on.
However, I've had an experience when I was driving on the freeway when the CEL would flash on then off after hitting slight bump. The stored code was a p0300, p0302. Switch the coils and the problem did not follow and I have not seen that issue since.

Maybe you might want to check whether there were any stored codes.

 

[LibertyTC]

Thanks!
Could the resistance value somehow be effected by over tightening the 10mm coil nut?
Is there a torque spec for that nut?

 

[uss2defiant]

No.

From my cheatsheet, it is 70 in-lbs.

 

[LibertyTC]

Readings with alligator clips were inconclusive.
Only with the most secure connection was I able to get it to read properly.
I think I need to build a coil test connector & wire set up to clip onto, for proper connections.
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Got the 6th spark plug installed today, no change..engine shake, could it be fuel related?
IDK but I think the Jeep is going into the shop for a full scan/Diagnostic w/live data.
My bud just spend $ 7K on the latest Snap On Diagnostics...
Will see how he does to figure it out. Going to be a while before I got time to mess around more with this.

 

[uss2defiant]

they do sell those. I think I saw one in NAPA.
Honestly, 6k to 9k ohm is a pretty wide range.
OK is good enough.

 

[LibertyTC]

They sell what? A new connector with bare wire end or?
Sure would like to find a secure coil connection.
Ok is good enough..ya I agree.
It is too bad my motor still shakes a bit, and fells like something's fubar..
Drive's ok & still shifts ok..Looks like the KJ's headed into the shop soon.

 

[uss2defiant]

I saw it in a clearance bin, which had a connector to a banana and another banana to a rod to test the secondary resistance.

Can't seem to google it. All I see are spark testers.

 

[tjkj2002]

Readings with alligator clips were inconclusive.
Only with the most secure connection was I able to get it to read properly.
I think I need to build a coil test connector & wire set up to clip onto, for proper connections.
52108[/ATTACH]"]

You must be registered for see images attach

Got the 6th spark plug installed today, no change..engine shake, could it be fuel related?
IDK but I think the Jeep is going into the shop for a full scan/Diagnostic w/live data.
My bud just spend $ 7K on the latest Snap On Diagnostics...
Will see how he does to figure it out. Going to be a while before I got time to mess around more with this.

I gave up long ago testing coils,had to many pass the tests but are still bad.I just replace the coil(s) with known good ones.Granted I do have a nice selection of different known good coils from being a tech.

 

[profdlp]

Forgive the n00b question, but what all is in there, anyway?

 

[uss2defiant]

Ignition coil - Wikipedia, the free encyclopedia

 

[LibertyTC]

My engine shake may be normal. The first time I felt it my first observation was something seems out of balance.....
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