How to Test Lawn Mower Ignition Coil: A Simple DIY Guide

A sputtering lawn mower can be a frustrating experience, especially when you’re eager to get your yard looking its best. One of the most common culprits behind a lawn mower’s refusal to start is a faulty ignition coil. This crucial component is responsible for delivering the spark that ignites the fuel-air mixture in your engine. So, if your lawn mower is acting up, knowing how to test lawn mower ignition coil is a valuable skill to have.

Understanding the Ignition Coil’s Role

The ignition coil is a small but vital part of your lawn mower‘s engine. It acts as a transformer, converting the low voltage from the battery into a high-voltage spark that jumps the gap in the spark plug, igniting the fuel. Think of it as the electrical heart of your lawn mower. When the ignition coil malfunctions, the spark plug doesn’t receive the necessary energy to ignite the fuel, leading to a frustrating “no start” situation.

Common Signs of a Faulty Ignition Coil

Before diving into the testing process, it’s helpful to identify the telltale signs of a failing ignition coil. These symptoms can help you narrow down the problem and determine if testing the ignition coil is the right course of action:

• No Spark: This is the most obvious sign. If you can’t see a spark at the spark plug, the ignition coil is likely the culprit.
• Engine Cranks but Won’t Start: The engine turns over but fails to ignite, indicating a lack of spark.
• Intermittent Starting Issues: The lawn mower starts sometimes but fails to start other times, suggesting a faulty coil that’s intermittently delivering a spark.
• Backfiring or Misfiring: An inconsistent spark can lead to backfiring or misfiring, creating a rough and erratic engine operation.

Safety First: Essential Precautions

Before you begin testing your ignition coil, it’s crucial to prioritize safety.

• Disconnect the Battery: Always disconnect the battery cables (both positive and negative) before working on any electrical components in your lawn mower. This prevents accidental shocks and ensures your safety.
• Wear Eye Protection: Wear safety glasses to protect your eyes from any potential debris or sparks.
• Use Insulated Tools: Use insulated screwdrivers and pliers to avoid contact with live electrical components.

How to Test Lawn Mower Ignition Coil: Step-by-Step Guide

Now, let’s get into the practical aspect of testing your ignition coil. You’ll need a few basic tools:

• Multimeter: A multimeter is essential for measuring resistance and voltage.
• Spark Plug Wrench: This is used to remove and install the spark plug.
• Wire Brush: A wire brush helps clean the spark plug terminals for optimal conductivity.

Here’s a step-by-step guide on how to test lawn mower ignition coil:

Step 1: Disconnect the Battery

Disconnect the battery cables (positive and negative) to prevent any accidental electrical shocks.

Step 2: Locate the Ignition Coil

The ignition coil is usually located near the spark plug, often mounted on the engine block or cylinder head. It’s typically a small, cylindrical component with a wire leading to the spark plug.

Step 3: Remove the Spark Plug

Using the spark plug wrench, carefully remove the spark plug from the engine.

Step 4: Inspect the Spark Plug

Examine the spark plug for signs of wear, fouling, or damage. If necessary, clean the terminals with a wire brush to ensure good conductivity.

Step 5: Connect the Multimeter

Set your multimeter to the resistance (ohms) setting. Connect the multimeter probes to the two terminals on the ignition coil.

Step 6: Measure Resistance

The ignition coil should have a specific resistance value. Consult your lawn mower’s manual or an online resource to find the correct resistance range for your specific model.

• If the resistance reading is within the specified range: The ignition coil is likely functioning properly.
• If the resistance reading is outside the specified range: The ignition coil is likely faulty and needs replacement.

Step 7: Test for Spark (Optional)

If you have a spark tester, you can further confirm the ignition coil‘s functionality by testing for spark.

• Connect the spark tester: Connect the spark tester to the spark plug wire.
• Ground the spark tester: Ground the spark tester to a metal part of the engine.
• Crank the engine: Turn the engine over.
• Observe the spark tester: A healthy ignition coil should produce a bright blue spark.

Troubleshooting and Replacing the Ignition Coil

If your tests indicate a faulty ignition coil, it’s time to replace it.

• Locate a Replacement Coil: Find a new ignition coil that’s compatible with your lawn mower model. You can consult your owner’s manual or search online for the correct part.
• Disconnect the Battery: Always disconnect the battery before working on any electrical components.
• Remove the Old Coil: Carefully remove the old ignition coil from its mounting location.
• Install the New Coil: Install the new ignition coil in the same location as the old one, ensuring it’s securely fastened.
• Connect the Wires: Connect the wires to the new ignition coil, matching them to their corresponding terminals.
• Reconnect the Battery: Reconnect the battery cables, making sure the positive (+) and negative (-) terminals are properly connected.

Beyond the Ignition Coil: Other Potential Issues

While a faulty ignition coil is a common culprit, other issues can prevent your lawn mower from starting. Here are some additional troubleshooting tips:

• Check the Spark Plug: A fouled or damaged spark plug can also prevent your lawn mower from starting. Clean or replace the spark plug if necessary.
• Inspect the Fuel System: Ensure your fuel tank has fresh fuel and that the fuel lines are clear of any blockages.
• Check the Air Filter: A clogged air filter can restrict airflow to the engine, preventing it from starting.
• Verify the Battery: A weak or dead battery can also hinder starting. Check the battery voltage with a multimeter.

Maintaining Your Lawn Mower for Longevity

Regular maintenance can help prevent many common lawn mower problems, including ignition coil failures.

• Change the Spark Plug Regularly: Replace the spark plug according to the manufacturer’s recommendations.
• Keep the Air Filter Clean: Clean or replace the air filter regularly.
• Use Fresh Fuel: Use fresh, high-quality fuel and avoid storing fuel for extended periods.
• Inspect and Clean Components: Regularly inspect and clean other engine components, such as the carburetor and fuel lines.

Keeping Your Lawn Mower Running Smoothly

Understanding how to test lawn mower ignition coil empowers you to diagnose and fix common starting problems. By following these steps and performing regular maintenance, you can keep your lawn mower running smoothly and efficiently, ensuring a healthy, well-maintained lawn.

Answers to Your Most Common Questions

Q: How long does a lawn mower ignition coil typically last?

A: The lifespan of an ignition coil can vary depending on factors like usage, maintenance, and environmental conditions. Generally, they can last for several years, but it’s a good idea to inspect and test them regularly, especially if you notice starting issues.

Q: Can I use a universal ignition coil on my lawn mower?

A: While universal ignition coils are available, it’s crucial to ensure they are compatible with your specific lawn mower model. Check the specifications and ensure the coil’s resistance and output voltage match your lawn mower’s requirements.

Q: What if I don’t have a multimeter?

A: If you don’t have a multimeter, you can still test the ignition coil by using a spark tester. However, a multimeter provides a more comprehensive assessment of the ignition coil’s health.

Q: What are some common causes of an ignition coil failing?

A: Common causes of ignition coil failure include:

• Heat damage: Overheating can damage the coil’s internal components.
• Moisture: Exposure to moisture can cause corrosion and short circuits.
• Vibration: Constant vibration can wear down the coil’s internal connections.
• Age: Like any electrical component, ignition coils have a limited lifespan.