The ignition coil module is a critical component in the ignition system of any gasoline-powered vehicle. Its primary function is to convert the battery’s low voltage into the high voltage necessary to create a spark at the spark plugs, igniting the fuel in the engine. When an ignition coil starts to fail, it can result in engine misfires, poor fuel economy, and even engine stalling. Testing the ignition coil module is an essential step in diagnosing engine issues. This blog article will guide you through how to test an ignition coil module in detail.
What is an Ignition Coil Module?
The Role of the Ignition Coil in the Engine
The ignition coil module plays a pivotal role in the functioning of a vehicle’s engine. It takes the 12 volts from the vehicle’s battery and amplifies it to as much as 30,000 volts or more. This high voltage is needed to create a spark in the spark plugs, which then ignites the air-fuel mixture in the engine cylinders, producing the power that propels the vehicle.
Types of Ignition Coils
Ignition coils can come in different types depending on the vehicle’s make and model. Some common types include:
- Single-spark ignition coils: These are individual coils for each cylinder.
- Distributor-based ignition coils: In older vehicles, a single ignition coil is used along with a distributor.
- Coil-on-plug (COP) systems: In modern vehicles, each spark plug has its own ignition coil directly mounted on top of it.
Signs of a Failing Ignition Coil Module
Before testing your ignition coil module, it’s important to understand some of the symptoms that may indicate a failure:
- Engine misfire: If one or more ignition coils are faulty, the engine can misfire, causing a rough idle.
- Poor fuel economy: A failing coil can lead to incomplete combustion, resulting in wasted fuel.
- Check engine light: In many cases, a failing ignition coil will trigger the check engine light.
- Difficulty starting: Without a strong spark, the engine may struggle to start, especially in cold conditions.
Tools Needed for Testing an Ignition Coil Module
Essential Tools
Before you begin testing, you’ll need the following tools:
- Multimeter: A digital or analog multimeter is used to measure the resistance and voltage of the ignition coil.
- Spark tester: A tool designed to check whether a spark is being generated by the ignition coil.
- Socket wrench set: Necessary for removing the ignition coil if it needs to be physically inspected or replaced.
- Safety gloves and glasses: Always take safety precautions when working with electrical components.
Step-by-Step Guide: How to Test an Ignition Coil Module
1. Locate the Ignition Coil Module
The first step is to locate the ignition coil module in your vehicle. This can vary depending on the type of ignition system your vehicle has:
- For vehicles with a coil-on-plug (COP) system, the coils are mounted directly on top of the spark plugs.
- In vehicles with a distributor-based system, the ignition coil is usually mounted near the distributor.
Refer to your vehicle’s service manual to confirm the exact location of the ignition coil module.
2. Perform a Visual Inspection
Before performing any tests, visually inspect the ignition coil and its wiring for any obvious signs of damage:
- Cracks or burn marks: These can indicate that the coil has overheated or shorted out.
- Corrosion: Check the connections for any signs of corrosion, which can disrupt the electrical connection.
3. Test the Primary and Secondary Resistance with a Multimeter
The next step involves using a multimeter to test the resistance of the ignition coil. Ignition coils have two sets of windings: the primary and secondary windings. Both need to be tested.
Testing the Primary Windings
- Set the multimeter to the ohms (Ω) setting.
- Connect the multimeter’s leads to the two terminals on the ignition coil’s primary side. These are usually the smaller terminals.
- Check the reading on the multimeter. Refer to your vehicle’s service manual for the acceptable range, but typically the resistance should be between 0.4 to 2 ohms.
- If the resistance is too high or too low, the coil is likely faulty.
Testing the Secondary Windings
- Move the multimeter leads to the secondary winding terminals. This is usually between one of the primary terminals and the high-tension terminal (the output terminal that connects to the spark plug).
- Check the multimeter reading. The acceptable range for the secondary winding is typically between 6,000 to 10,000 ohms. Refer to your vehicle’s manual for the exact specifications.
- If the reading is outside this range, the ignition coil may be faulty and require replacement.
4. Perform a Spark Test
Using a Spark Tester
- Disconnect the ignition coil from the spark plug and insert the spark tester into the coil’s spark plug lead.
- Ground the spark tester to a metal part of the engine.
- Crank the engine and observe the tester.
- If you see a strong, blue spark, the ignition coil is functioning properly.
- If the spark is weak or non-existent, the ignition coil may be faulty.
5. Voltage Test
You can also use a multimeter to test the voltage going into the ignition coil.
- Set your multimeter to the volts (V) setting.
- Turn the ignition to the “On” position without starting the engine.
- Probe the positive terminal of the ignition coil with the multimeter’s positive lead and the negative terminal or a ground with the multimeter’s negative lead.
- The voltage reading should match your vehicle’s battery voltage (around 12 volts). If there is no voltage, there may be an issue with the vehicle’s electrical system, not the ignition coil.
Common Problems Found in Ignition Coil Modules
Coil Overheating
Ignition coils can sometimes overheat due to excessive electrical resistance or poor cooling in the engine bay. Overheating can lead to internal damage in the coil, which can cause it to fail prematurely.
Electrical Arcing
Another common issue is electrical arcing, where the coil discharges electricity in an unintended path. This can be caused by damaged insulation or faulty wiring.
Moisture Damage
In some cases, moisture can seep into the ignition coil, especially in vehicles that are frequently exposed to damp conditions. This can lead to short circuits and corrosion.
When to Replace an Ignition Coil Module
If the ignition coil fails any of the tests mentioned above, it is likely time to replace it. It’s important to use a high-quality replacement part to ensure proper engine performance. Ignoring a faulty ignition coil can lead to further engine damage and costly repairs down the road.
How to Replace an Ignition Coil
- Disconnect the negative battery terminal.
- Unplug the wiring harness from the ignition coil.
- Remove any mounting bolts holding the ignition coil in place.
- Install the new ignition coil and reconnect the wiring harness.
- Reconnect the battery and test the engine to ensure everything is working correctly.
Conclusion
Testing an ignition coil module is a straightforward process, but it requires attention to detail and the right tools. By following the steps outlined in this guide, you can diagnose whether your ignition coil is functioning properly or if it needs to be replaced. Regular maintenance and timely repairs of the ignition system will help keep your engine running smoothly and efficiently.
