In this article I'll show you a very simple, easy and highly accurate way to see if the ignition coil on your 4.9L, 5.0L, 5.8L Ford F150 (or E150, Bronco, Crown Victoria, Grand Marquis, etc) is fried and causing your vehicle to NOT START or not the cause of the problem.
The test you'll be doing is an on car test done with the ignition coil in action. You won't need any expensive testing equipment to follow the simple step-by-step testing instructions presented here. You'll need a spark tester, a multimeter, a 12 volt test light, and a helper (to assist you in cranking the engine).
If you're looking for the resistance test of the primary and secondary circuits, this article will not help you (in my opinion, the primary/secondary resistance test is a complete waste of time and life that does not work around 99% of the time to diagnose a BAD ignition coil).
To help you navigate this article a little easier, here are its contents at a quick glance:
You can find this tutorial in Spanish here: Cómo Probar la Bobina de Encendido (Ford 4.9L, 5.0L, 5.8L) (at: autotecnico-online.com).
TIP 1: The ignition coil test, I'm gonna show you here, is done with the engine cranking and so you've got be careful and stay alert. Take all necessary safety precautions.
TIP 2: You'll need a helper to help you crank the engine. I suggest that you keep him or her outside the vehicle till you need him (or her) to crank the engine. Your helper should stay outside the vehicle and away from the ignition switch before and after you set up the test.
TIP 3: The ignition coil is not the only thing that can cause a cranks but does not start condition, when it fails. Other components can fail and provoke a no start.
If you have already replaced the ignition coil or the tests in this tutorial show that it's good... the following tutorial may be of help:
This may seem like a no brainer because the most obvious symptom of a BAD ignition coil is a no start no spark condition, but here are a few other symptoms you'll see along with no spark:
The one thing to remember, if you do find out that the ignition coil failed, is that the engine will be flooded with gasoline and this may require that you remove the gasoline fouled spark plugs to dry them out (or your vehicle may still not start).
Now, and in case you're wondering... finding out if the lack of spark is caused by a bad ignition coil or a bad ignition control module is not hard. It's something that you can do without removing these parts (to replace them and see which one solves the no spark-no start problem) and in this tutorial I'll show you how.
Although the following explanation is not theory heavy or full of big technical words/terms, it will help you to see how the ignition coil works.
Knowing a little practical working theory will answer a lot of questions that the article doesn't answer.
It all starts when you turn the key and start cranking the engine... and in a nutshell, this is what happens:
In the next page we'll jump right into the first ignition coil test...
“A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.”