Rockheadsson

I'm in the process of troubleshooting potential reasons for why my Jeep cranks and will not start. Earlier today I pulled the ignition coil to probe it with my multimeter.

1. From stud to stud in the plug, I got 1.9 ohms.

2. From left plug stud to main output stud I got around 10,000 ohms. Same went for right plug stud to main output stud.

Are these normal values, and is there a way to verify that the coil is sparking correctly when I am cranking?

Thanks!

P.S. I know that these questions have been answered over time throughout different threads, but I was hoping to get some sort of compendium of answers.

tjwalker

Get a manual which will outline the exact testing procedure. Everybody that works on their XJ should have one. Here is a link to an inexpensive, licensed legal service manual. Only $7.95

http://www.pacificcoastmanuals.com/F..._cherokee.html

You will be testing both primary and secondary resistances.

Do you have SPARK? If not, the #1 cause of that is the crankshaft position sensor. The #2 cause is the ignition coil. Both can be tested, but testing of the crank sensor may not be conclusive. If you do buy a crank sensor, do yourself a big favor and buy it directly from Jeep. Aftermarket crank sensors are "hit and miss" with a whole lot of miss.

Good luck and keep us updated!

car5car

"2005-2008 Jeep Cherokee WK Factory Service Manual" ??????????????????/?//

rompnXJ

click on his link, look on the right side of the computer screen and you'll see a vertical bar with arrows at the top and bottom, click the bottom one a few times and the page will move; the service manuals for the XJ should then become visible

rompnXJ

OP, get yourself one of these:

http://www.harborfreight.com/inline-...ker-69014.html

and install it between the coil and the distributor cap. if it doesnt flash, that means the coil is not sparking for whatever reason; possibly the coil is not properly grounded or is not receiving power/signal, or the coil may be shot. check all your grounds & fuses, and inspect the coil for cracks in its housing if it does start flashing, you have spark from the coil, which would indicate your problem lies elsewhere.

Radi

Roughly 1 ohm on the primary and 12,000-13,000 on the secondary.
Can't always find a bad coil with a resistance test though. They sometimes hold together fine on the low voltage from the DMM but short like crazy under high voltage.

You should have battery voltage (12-13V) on the positive primary coil connector and about half that on the negative while cranking. If the positive and negative primary connectors show the exact same voltage while cranking, the ECU isn't trying to fire the coil. That's often a bad CPS

rrich

Even when it passes all Ohms tests is still could be bad.

The quickest and simplest test is easy, and very definitive.

Remove a plug wire, hold it about 1/4" from ground and have someone crank the engine or even start it. You'll need insulted pliers to hold it.

Check the COLOR of the spark it's a great indication of the secondary voltage. If the insulation inside the coil is breaking down, it limits the voltage the coil can provide.

It should be a "CRISPY" SNAPPY BRIGHT BLUE SPARK - any other color indicates a lower voltage.
White, yellow, or red is not near enough voltage.

If it's not the desired blue, check the color right at the coil tower. If it's still not blue, replace coil.
If it's blue at the coil tower but not at a plug - replace coil wire!

Secondary insulation breakdown is very common on the Jeep coils.
Aftermarket coils or cheapie coils from China don't last long. The so-called "Hi Performance" are not really what they say they are.
A good quality stock coil will outperform them all, and last longer - and they are not expensive.

Kalali

Never mind