Unleash Your Lawn Mower’s Potential: How to Test Ignition Coil with Multimeter

Starting your lawnmower and hearing a frustrating “click” instead of the satisfying roar of the engine can be incredibly frustrating. One common culprit behind this issue is a faulty ignition coil. This critical component is responsible for generating the high-voltage spark that ignites the fuel-air mixture in your mower’s engine. Knowing how to test a lawn mower ignition coil with a multimeter can save you time and money by diagnosing the problem accurately before replacing parts unnecessarily.

Understanding the Ignition Coil

Before diving into the testing process, let’s understand what the ignition coil does and its role in your lawnmower’s engine. The ignition coil is a transformer that steps up the low voltage from your mower’s battery to a high voltage, typically around 10,000 to 30,000 volts. This high voltage is then delivered to the spark plugs, generating a spark that ignites the fuel-air mixture in the combustion chamber.

Symptoms of a Faulty Ignition Coil

Several symptoms can indicate a faulty ignition coil. Here are some common signs:

• No spark at the spark plug: This is the most obvious sign of a faulty ignition coil. If you’re not getting any spark at the spark plug, the ignition coil is likely the culprit.
• Engine misfires: If your engine is sputtering or misfiring, it could be due to a weak spark from a failing ignition coil.
• Difficulty starting: If your mower struggles to start or takes a long time to fire up, a faulty ignition coil could be preventing the engine from getting the necessary spark.
• Engine dies unexpectedly: If your mower suddenly dies while running, it could be due to a loss of spark from the ignition coil.

Tools You’ll Need

To test your lawnmower’s ignition coil, you’ll need the following tools:

• Multimeter: A digital multimeter is essential for this test. It allows you to measure resistance and continuity, which are crucial for diagnosing a faulty ignition coil.
• Spark plug wrench: This tool is needed to remove and inspect the spark plug.
• Wire brush: A wire brush will help clean the spark plug electrode and ensure a good connection.
• Safety glasses: Always wear safety glasses when working with tools and electrical components.

Testing the Ignition Coil with a Multimeter

Now, let’s move on to the actual testing process:

1. Disconnect the Ignition Coil

Begin by disconnecting the ignition coil from the spark plug wire. This is usually done by pulling the wire connector off the ignition coil.

2. Set Your Multimeter to Resistance Mode

Turn on your multimeter and set it to the “ohms” setting. This allows you to measure resistance, which is a crucial indicator of the ignition coil‘s health.

3. Connect the Multimeter Leads to the Ignition Coil Terminals

Most ignition coils have two terminals: a primary terminal and a secondary terminal. Connect one multimeter lead to the primary terminal and the other lead to the secondary terminal.

4. Check for Continuity

With the multimeter leads connected, observe the reading on the multimeter display. A healthy ignition coil should show a resistance reading between 0.5 and 5 ohms. If you get a reading of “OL” (open circuit) or a very high resistance, it indicates a problem with the ignition coil and likely requires replacement.

5. Test the Spark Plug Wire

After testing the ignition coil, it’s good practice to also test the spark plug wire for continuity. Disconnect the wire from the spark plug and connect one multimeter lead to the wire terminal and the other lead to the spark plug end. A healthy wire should show a resistance reading between 0 and 10,000 ohms. If you get an open circuit or a very high resistance, the wire may be faulty and need replacement.

Troubleshooting Tips

• Check the spark plug: If the ignition coil tests good, but you still don’t have a spark, check the spark plug. A fouled or worn-out spark plug can prevent a spark from jumping.
• Inspect the wiring: Look for any loose or corroded wires in the ignition system. These can cause an interruption in the electrical circuit and prevent a spark.
• Clean the spark plug: A dirty spark plug can prevent a spark from jumping. Clean the spark plug electrodes with a wire brush and ensure a good connection.

Replacing a Faulty Ignition Coil

If your ignition coil tests faulty, you’ll need to replace it. Here are some tips for replacing the ignition coil:

• Purchase the correct replacement: Ensure you purchase a replacement ignition coil that is specifically designed for your lawnmower model. Don’t use a generic coil as it may not have the correct specifications.
• Disconnect the battery: Before replacing the ignition coil, disconnect the battery to prevent electrical shock.
• Follow the manufacturer’s instructions: Refer to your lawnmower’s owner’s manual or consult a repair guide for detailed instructions on replacing the ignition coil.

Replacing a Faulty Ignition Coil: A Success Story

Here’s a real-life example of how testing an ignition coil with a multimeter helped a homeowner troubleshoot a lawnmower problem:

“My lawnmower wouldn’t start, and I couldn’t figure out why. I checked the fuel, spark plug, and air filter, but nothing seemed to be wrong. I then decided to test the ignition coil with a multimeter, and it showed a high resistance reading. I replaced the ignition coil, and the mower started right up! It was such a simple fix, and I saved myself a lot of time and money by testing the coil first.”

Final Thoughts: Beyond the Spark

Testing a lawnmower ignition coil with a multimeter is a crucial step in diagnosing engine starting problems. This simple test can save you time and money by identifying the issue quickly. However, remember that other factors can also contribute to starting problems, such as a faulty spark plug, clogged fuel lines, or a blocked air filter. By systematically checking these components, you can increase your chances of successfully troubleshooting and repairing your lawnmower.

Answers to Your Most Common Questions

Q1: How often should I test my lawnmower’s ignition coil?

A1: It’s generally a good idea to test your ignition coil every season before starting your lawnmower. This helps catch any potential problems early on.

Q2: Can I use a regular multimeter to test the ignition coil?

A2: Yes, you can use a regular multimeter to test the ignition coil. Just make sure it has a resistance setting.

Q3: What should I do if my ignition coil tests good, but I still don’t have a spark?

A3: If the ignition coil tests good, but you still don’t have a spark, check the spark plug, spark plug wire, and wiring for any issues.

Q4: Can I replace the ignition coil myself?

A4: Yes, you can replace the ignition coil yourself. However, it’s important to follow the manufacturer’s instructions carefully and disconnect the battery before working on the electrical system.

Q5: How much does a new ignition coil cost?

A5: The cost of a new ignition coil can vary depending on the make and model of your lawnmower. You can typically find replacement coils for around $20 to $50.