What can I do to fix no fire to cylinder 1?

Question

I have a 2008 Jeep Wrangler X manual 3.8 with no fire to #1. Recently replaced injectors, plugs, wires, coil pack, egr and other items. Still no fire what next?

jack62 · Accepted Answer

Check for spark at the coil pack on the "number 1 coil" towers' for cylinders 1 & 4.

If you have spark on 4 but no spark on 1, then the coil pack is faulty.

Here's why. It's a wasted spark coil pack design.

There's 3 coils in the coil pack which provide spark to the 6 cylinders.

It looks like this:

The computer has 3 ignition coil drivers in it. Each driver provides a ground signal which fires each of the 3 ignition coils.

It's wired like this:

When it sends the ground signal to "spark" the #1 coil, spark is produced at ignition coil towers 1 & 4.

Likewise when it sends a ground signal to ignition coil #2. Spark is produced at ignition coil towers 2 & 5.

And when it sends a ground signal to coil #3, spark is produced at ignition coil towers 3 and 6.

So if you have spark on coil tower 4, but no spark on coil tower 1, you know the computer's ignition coil 1 driver is providing the ground signal to fire the #1 coil. (that tells you the #1 ignition coil driver in the computer is good and the wiring from the pcm to the ignition coil pack is also good).

Here's a link which you may find useful in your troubleshooting:

https://easyautodiagnostics.com/chrysler/3.3L-3.8L/testing-the-coil-pack-1

People tend to "fog out" when things are referred to as "drivers".

Your ignition coil "drivers" are simply transistors on the printed circuit board.

They're just electronic switches that can "turn on" Ground to each ignition coil and turn off" Ground to each ignition coil. When they "turn on" Ground, the ignition coil produces spark.

You have 3 of them on your ECM circuit board and they look like this:

My point being, sometimes when an ignition coil shorts out it can fry its driver (transistor) on the ECM circuit board.

Or it could damage the wiring from the ECM to the coil pack.

If you have spark on the coil tower for the #4 cylinder, but no spark on the coil tower for the #1 cylinder, that didn't happen

G.T. · Answer

What about the distributor? Have you checked it? Check also solutions there: https://carkiller.com/scottykilmer/qa/i-have-no-spark/