Generally speaking, the Distributor-less type can be divided into two basic categories:
- Coil-on-Plug. This type of setup has an individual ignition coil for each cylinder sitting right on top of the spark plug.
- Ignition Coil pack type. In this type, all of the ignition coils are housed in one unit.
Coil pack type Ignition Systems can be found in vehicles from Ford, Chrysler, General Motors (like Chevrolet, Buick, Oldsmobile, Pontiac, etc.) and imports like Mazda, etc .
The Testing Tips in this article apply only to coil pack type ignition coils like the ones pictured below.
The photo on the left is of a 2003 Dodge Neon (2.0L 4 cylinder) and the one on the right of a 2000 Ford Taurus (3.0L V6).
Testing these ignition coils can be done on the car or off the car. Both testing methods are easy. I'll explain the ON CAR test here and the tools you'll need to accomplish them.
You may want to acquaint yourself with the basic working theory of the ignition coil. If so, I recommend reading the following article (within this site) Ignition System Basics: How Does An Ignition Coil Work
Each individual ignition coil, within the coil pack, needs two things to create spark.
- 12 Volts.
- And the switching signal from the Switching Device.
In analysing the above two statements you may be asking what the heck is the Switching Signal and the Switching Device? Here are the basic definitions/descriptions:
- Switching Device: In the real world this device is normally called the: Ignition Control Module or the Igniter. For the most part, they are located within the fuel injection computer in newer vehicles. On older vehicles, the Ignition Control Module is located outside the computer, somewhere in the engine compartment.
- Switching Signal: This is the ON/OFF control signal from the ignition module. More specifically: ON is when the module allows the voltage flowing thru' the individual coil to reach ground. OFF is when the module interrupts this path to ground. This turning OFF of the ground circuit causes a spark to jump out of the individual ignition coil in the coil pack.
OK, that was simple enough. Knowing the above will help you understand and interpret the results of the tests you're gonna' perform. The basic layout of the test is as follows:
- Perform a spark test.
- Test for 12 volts first.
- Test for the Switching Signal.
- Interpret the results at each step.
Alright, lets turn the page and get started with the very first thing: The Spark Test.