Outboard Ignition System FAQ
Many running problems can be traced back to the ignition system. This page will cover a few troubleshooting tips & tricks, but it's definitely not a replacement for the proper tools and service manual. Also, keep in mind that some ignition components cannot be tested without a peak reading volt meter, or a Fluke meter with the CDI #511-9773 DVA attachment, which we have available for $85. Feel free to use the FAQ Submission Form, if you'd like to suggest a question that you feel should be covered here.
How do I troubleshoot the ignition system?
The short answer is, "follow the steps in the manual for your motor," since it varies with the different ignition systems out there. But sometimes, it's as simple as basic math. Count the number of cylinders on your motor, look at the different components and what they do, then see how many cylinders are missing spark. As a quick example, let's say you have a V6 with a stator, a trigger (timer base), two ignition modules (power pack/switch box), 6 coils, 6 plug wires and 6 spark plugs. Still with me? Good!
In this example, it's very likely that the stator supplies power to all 6 cylinders, each ignition module is responsible for one bank of 3 cylinders, the trigger probably fires groups of 2 cylinders, then each cylinder will have it's own coil, plug and plug wire.
So, how many cylinders don't have spark? If the answer is one, you'll probably want to focus on the coils, spark plugs and plug wires. If it's two, or even four, I'd suspect the trigger first. Three? Most likely an ignition module, but don't rule out the stator just yet. Try switching the modules around. If the problem moves to the other 3 cylinders, then it's probably the module. If it stays on the same three, it's probably the stator.
Do I really need a peak reading volt meter?
It is the best way to troubleshoot the an outboard ignition system, but sometimes there are ways around it. In some cases, the service manual will have resistance tests that will help you narrow it down with a standard ohm meter.
There are also some cases where you can narrow it down by switching parts around.
Can I just switch parts around to see what's bad?
Sometimes, yes. This method works best on motors that have two ignition modules (or one CDM module per cylinder), but on others, there isn't much to switch around besides the coils, plugs and plug wires.
You can also switch a part out with a known-to-be-good version of the same part. This could be an option for people that have two of the same motor, or a friend that has a motor with the same system.
Just don't buy a new part for this kind of test because you probably won't find anyone that will let you return an ignition part if you're wrong. Note: In some cases, it could be possible to damage a good part by connecting it to a bad part for testing purposes.
What is the best way to check spark?
It's best to use a spark checker, set to the recommended gap, which is usually 3/8 - 1/2 inch. You should see a strong blue spark when you crank the motor over.
Spark checkers make it easier to see if the cylinders are firing evenly, which makes it easier to narrow down an intermittent or weak spark problem.
There are also inline spark checkers that you can put on the each cylinder and run the motor. These can come in handy for narrowing down a high speed miss.
Some people use timing lights to check spark, or just hold the plug against ground while cranking. This is okay for basic checking, but keep in mind that neither of these will work with a fouled or defective spark plug.