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:
- Important Suggestions.
- Symptoms of a BAD Ignition Coil.
- How Does the Ignition Coil Work?
- IGNITION COIL TEST 1: Testing for Spark With a Spark Tester.
- IGNITION COIL TEST 2: Testing for Spark Directly on Coil's Tower.
- IGNITION COIL TEST 3: Verifying Ignition Coil is Getting 12 Volts.
- IGNITION COIL TEST 4: Verifying the Switching Signal With a Test Light
- Why the HEI Spark Tester.
- Where to Buy the Ignition Coil and Save.
- Related Test Articles.
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:
Symptoms of a BAD Ignition Coil
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:
- None of the spark plugs will fire spark.
- The fuel pump will still work.
- The PCM will still activate the fuel injectors.
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.
How Does the Ignition Coil Work?
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:
- The ignition control module (ICM) and the ignition coil get power (12 volts).
- Power is supplied to the ignition coil thru' the wire labeled with the number 2.
- The profile ignition pickup (PIP) sensor, which is what Ford calls the crank sensor, gets power from the ICM and as the engine cranks it starts to generate a crankshaft position signal (called the PIP signal).
- This PIP signal is then sent to and received by the ignition control module (ICM).
- When the ICM gets the PIP signal, it starts to switch the ignition coil ON and OFF by interrupting the ignition coil's primary voltage.
- What this means in plain English is that the ignition module interrupts the ignition coil's battery power ON and then OFF. How? By closing and then opening the ground circuit this ignition coil's battery power needs to get to ground.
- The action of switching ON and OFF the primary voltage (ignition coil's battery power) is referred to as the switching signal.
- Once the ignition coil gets this switching signal, it starts to spark away and as you're already aware, this spark gets delivered to the center of the distributor cap by a high tension wire.
- From this point, the distributor rotor distributes the spark to the cylinders across the spark plug wires.
- By this time, the fuel injection computer is also injecting fuel into the engine, which the spark will ignite... thus the engine starts!
In the next page we'll jump right into the first ignition coil test...