TEST 3: Two Dead Cylinders Diagnostic
Having a coil pack with 2 towers that are not sparking is the most common type of failure with this type of Ford ignition control module (ICM).
To understand this phenomena (two coil pack towers from the same coil pack not sparking), you and I need to know that each coil pack fires spark to 2 spark plugs at the exact same time (this is known as a Waste Spark ignition system). Here are the specifics:
- Each coil pack feeds 4 spark plugs.
- Spark plugs for cylinders #1 and #4 get spark at the exact same time.
- Spark plugs for cylinders #2 and #3 get spark at the exact same time.
- These cylinders are referred to as ‘Paired Cylinders’.
- Each coil pack fires spark to spark plugs on one side of the engine.
- Spark Plugs on the side of the exhaust manifold are called: Exhaust Side Spark Plugs.
- Spark Plugs on the side of the intake manifold are called: Intake Side Spark Plugs.
- Each coil pack is made up of 2 individual ignition coils.
- Each coil has 2 towers.
- When the individual ignition coil (within the coil pack) fires, this spark is sent out on both towers.
- Each coil pack has 3 wires
- The middle wire is the one that supplies Power (ignition voltage -12 Volts) to both individual ignition coils within the coil pack.
- The other 2 wires are the ones that supply an activation signal (known as the switching signal) to each individual ignition coil.
And so when you have 2 towers from the same coil pack not firing spark, it's usually due to one of two reasons: 1.) the coil pack is bad or 2.) the ignition control module (ICM) has fried internally and is not activating that specific ignition coil within the coil pack (although it will activate the others).
Having the 2.3L Ford ignition control module (ICM) fry in this way (where it doesn't activate one of the individual ignition coils within the coil pack) is the most common problem of the two and can be very easily tested.
OK, to find out if this is the case on your 2.3L Ford Mustang or Ranger (or 2.3L Mazda B2300), this is what you'll need to do:
- Find out which 2 coil pack towers are not firing spark.
- Remember, what you're looking for is No Spark from 2 coil pack towers that fire ‘Paired Cylinders’:
- Towers that feed spark to cylinders #2 and #3 are ‘Paired’.
- Towers that feed spark to cylinders #1 and #4 are ‘Paired’.
- NOTE: If you have No Spark from any other towers that are not ‘Paired’ (like No Spark from Cyl #1 and #3), then the ignition control module is not at fault and this tutorial won't help you.
- Once you have found out which coil pack and which 2 of its towers are not firing spark, choose from one of the following CASES below.
Choose one of the following CASES:
CASE 1: No Spark Cylinders #1 and #4 (EXHAUST SIDE).
- Go to TEST 4.
CASE 2: No Spark Cylinders #2 and #3 (EXHAUST SIDE).
- Go to TEST 5.
CASE 3: No Spark Cylinders #1 and #4 (INTAKE SIDE).
- Go to TEST 6.
CASE 4: No Spark Cylinders #2 and #3 (INTAKE SIDE).
- Go to TEST 7.
TEST 4: Testing Exhaust Side #1 And #4 (No Spark Condition)
This test will help you find out if the coil pack that feeds cylinders #1 and #4 on the exhaust side is bad or if the ignition control module is the one that's bad.
What you'll be doing, is checking for the ‘Switching Signal’ that the ignition module provides to the coil pack with a 12 Volt test light.
The instructions I'm providing below will have you testing for this ‘Switching Signal’ at the coil pack, but you can also test this signal at the ignition control module's bottom connector (although this is a bit harder due to a lack of access).
NOTE: This test is done with the engine cranking, in your 2.3L Ford Mustang or Ranger, so you've got to be careful and take all necessary safety precautions! Think Safety all of the time.
OK, to get this test going, this is what you'll need to do:
- Find the wire labeled with the number 3 of the exhaust side coil pack (in the photo above).
- NOTE: Remember, you're testing the coil pack that feeds the exhaust side spark plugs.
- The photo in the image viewer shows the coil pack with its spark plug wires off, this is just for illustration purposes (I had to remove them to take the photo of the connector). DO NOT remove the spark plug wires from the coil pack for this test.
- With your 12 Volt test light, pierce this wire a few inches away from the coil pack connector.
- Ground the 12 Volt test light's alligator clip directly on the battery positive (+) post.
- When ready, have a helper crank and start the engine while you observe the 12 Volt test light.
- NOTE: Both the coil pack and the ignition module must be connected to their connectors for this test.
- As the engine cranks, you should see one of 2 things:
- The 12 Volt test light will flash On and Off.
- The 12 Volt test light will NOT flash On and Off.
- NOTE: Whatever the test light does, when you turn the Key On and BEFORE you crank the engine DOES NOT matter, the result you want to look for is when the engine is cranking.
OK, let's interpret your test results:
CASE 1: The 12 Volt test light flashed On and Off. This tells you that the ignition control module (ICM) is working and activating the 2 towers that are not sparking.
Now, since the 2 towers are not sparking, this also tells you that the coil pack is bad. Replacing the coil pack will solve the problem of No Spark for exhaust side spark plugs for cylinder #1 and #4.
CASE 2: The 12 Volt test light DID NOT flash On and Off. This tells you that the ignition control module (ICM) is not activating the ignition coil (within the coil pack) that's responsible for firing spark to exhaust spark plugs #1 and #4.
Replace the ignition control module.