The hum of a lawnmower engine is the soundtrack of summer, but that familiar sound can quickly turn into silence if your ignition coil goes kaput. A faulty coil can leave you stranded with a stubborn lawn and a growing sense of frustration.
This article will walk you through the process of testing your lawn mower coil to determine if it’s the culprit behind your engine troubles. We’ll cover the basics of how a coil works, the tools you’ll need, and step-by-step instructions to test it effectively. By the end, you’ll be equipped to diagnose the problem and get your mower back in action.
Understanding the Ignition Coil: The Spark of Life
The ignition coil is a crucial component in your lawn mower’s engine. Its primary role is to transform low-voltage battery power into high-voltage electricity, which is then delivered to the spark plugs. This high-voltage spark ignites the air-fuel mixture in the combustion chamber, powering your mower.
A healthy coil delivers a strong, consistent spark, ensuring smooth and reliable engine operation. However, over time, coils can wear down, overheat, or become damaged, leading to a weak or absent spark. This can manifest in various symptoms like:
- Difficulty starting the engine: The engine may crank but fail to ignite.
- Rough running: The engine may sputter, misfire, or lose power.
- Engine dies unexpectedly: The engine might suddenly stop running while you’re mowing.
The Tools You’ll Need
Before you embark on testing your coil, gather these essential tools:
- Multimeter: This is your primary diagnostic tool, enabling you to measure electrical resistance and voltage.
- Spark plug wrench: Necessary for removing and reinstalling spark plugs.
- Screwdriver: For accessing the coil and other components.
- Safety glasses: Protect your eyes from potential debris and sparks.
- Gloves: For added protection and to ensure a clean working surface.
Testing the Ignition Coil: A Step-by-Step Guide
1. Disconnect the Spark Plug Wire
Begin by disconnecting the spark plug wire from the ignition coil. This is crucial for safety, preventing any accidental electric shock.
2. Locate the Ignition Coil and Identify its Terminals
The coil is typically found near the spark plug, often attached to the engine block. Identify the coil’s terminals:
- Primary Terminal: This terminal connects to the low-voltage side of the coil (connected to the battery).
- Secondary Terminal: This terminal connects to the high-voltage side of the coil (connected to the spark plug wire).
3. Set Your Multimeter to Resistance Measurement (Ohms)
Turn on your multimeter and select the resistance setting (often denoted by “Ω”).
4. Test the Primary Winding Resistance
- Touch the multimeter’s probes to the primary terminal on the coil and the ground (engine block or any metal part of the frame).
- Note the resistance value displayed on the multimeter. Consult your lawnmower’s manual or a reliable online source for the recommended resistance range for your specific coil model. If the reading falls outside this range, it indicates a problem with the primary winding.
5. Test the Secondary Winding Resistance
- Touch the multimeter’s probes to the secondary terminal on the coil and the spark plug wire connector.
- Record the resistance reading. Again, refer to your manual or a reliable resource for the expected resistance value for your coil. A reading outside the specified range suggests an issue with the secondary winding.
6. Visual Inspection
Carefully examine the ignition coil for any signs of damage, such as cracks, burns, or loose connections.
7. Test for Spark (Optional)
If you suspect a faulty coil, you can further confirm it by testing for spark. Disconnect the spark plug wire from the coil and hold it about 1/4 inch away from a grounded metal surface.
- While cranking the engine, observe if you see a bright blue spark jump between the wire tip and the metal surface. A weak or no spark indicates a problem with the coil.
Interpreting the Results
If your tests reveal an issue with the primary or secondary winding resistance, a damaged coil is likely the culprit. However, if the resistance readings are within the specified range but you still experience starting or running problems, the issue may lie elsewhere. Possible culprits include:
- Faulty spark plug: A fouled or damaged spark plug can also prevent proper ignition.
- Clogged fuel filter: A restricted fuel filter can hinder fuel flow to the engine.
- Fuel pump malfunction: A failing fuel pump may not deliver enough fuel to the carburetor.
- Bad ignition switch: A faulty ignition switch can interrupt the electrical flow to the coil.
Troubleshooting and Replacing the Coil
If you’ve confirmed that your ignition coil is faulty, it’s time to replace it.
- Purchase a new coil: Ensure you buy the correct coil for your specific lawnmower model.
- Install the new coil: Follow the manufacturer’s instructions for installation. Often, it’s as simple as disconnecting the old coil, removing the mounting bolts, and attaching the new one in the same position.
- Reconnect the spark plug wire: Make sure the wire is securely attached to the new coil’s secondary terminal.
- Test the engine: Start the engine and observe its performance.
Important Note: Before working on any electrical components, always disconnect the battery terminal to prevent accidental shocks.
Preventing Future Coil Problems
- Regular Maintenance: Perform routine maintenance on your lawn mower, including cleaning the spark plugs, checking the fuel filter, and inspecting the coil for any signs of wear or damage.
- Proper Fuel: Use high-quality gasoline, avoiding old or contaminated fuel.
- Avoid Overheating: Allow the engine to cool down properly after use.
- Storage: Store your lawn mower in a dry and clean environment during the off-season.
Conclusion
Testing your ignition coil can be a simple yet effective way to diagnose your lawn mower’s starting and running problems. By following the steps outlined in this guide, you can determine whether a faulty coil is the culprit and take the necessary steps to fix it. With a little time and effort, you can get your lawn mower back in tip-top shape and enjoy a lush, green lawn all summer long!
FAQ
Q1: What is a lawn mower coil and what does it do?
A lawn mower coil is a vital component of your engine’s ignition system. It acts as a transformer that converts the low voltage from your battery into a high voltage spark that ignites the fuel-air mixture in the engine’s combustion chamber. Without a functioning coil, your lawn mower won’t start.
Essentially, the coil receives a low-voltage signal from the ignition switch and converts it to a high-voltage spark. This spark is then directed to the spark plugs, which ignite the fuel and air mixture, allowing your lawn mower to run.
Q2: What are the signs of a dead lawn mower coil?
A dead lawn mower coil will exhibit several telltale signs, including:
- No start: The most obvious indication is that your lawn mower won’t start at all.
- Weak spark: If the coil is failing, you might see a weak spark at the spark plug, which may not be enough to ignite the fuel.
- Backfiring: A dead coil can sometimes cause backfiring, which occurs when the spark ignites the fuel-air mixture at the wrong time.
These signs suggest that the coil is not converting the low voltage into a high enough voltage spark to properly ignite the fuel mixture.
Q3: How can I test my lawn mower coil?
To test your lawn mower coil, you will need a basic multimeter.
- Disconnect the spark plug wire from the coil.
- Set your multimeter to the ohms setting.
- Connect one multimeter probe to the coil’s primary terminal and the other probe to the coil’s ground terminal.
- If the reading is within the coil’s specified resistance range, the coil is likely good.
If the reading is outside the specified range, it indicates that the coil is faulty and needs to be replaced.
Q4: What are the different types of lawn mower coils?
There are two primary types of lawn mower coils:
- Standard coils: These are the most common type and consist of a single coil that produces both the primary and secondary voltage.
- Dual coils: These coils have two separate coils – one for the primary voltage and one for the secondary voltage. Dual coils are often used in larger engines that require a higher voltage spark.
The type of coil used in your lawn mower will depend on the engine size and specifications.
Q5: Can I fix a dead lawn mower coil?
Unfortunately, lawn mower coils are not typically repairable. If you find that your coil is faulty, the best solution is to replace it with a new one.
Replacing a dead coil is usually a simple process, but it’s essential to ensure you purchase the correct replacement coil for your specific lawn mower model.
Q6: How do I choose the right replacement coil?
Choosing the right replacement coil is crucial for ensuring proper performance and longevity.
- Check your lawn mower’s manual: This will usually specify the correct coil type and part number.
- Check the coil itself: The part number is usually printed on the coil’s body.
- Contact your local lawn mower dealer: They can help you find the right coil for your specific model.
Always purchase a high-quality coil from a reputable manufacturer to ensure optimal performance and reliability.
Q7: How do I prevent my lawn mower coil from failing?
While there’s no guarantee to prevent a coil from failing entirely, proper maintenance can significantly prolong its lifespan.
- Keep your battery charged: A weak battery can stress the coil, leading to premature failure.
- Regularly inspect your ignition system: Look for signs of wear or damage, including cracked wires, corroded terminals, and loose connections.
- Use high-quality spark plugs: Damaged or worn-out spark plugs can put excessive strain on the coil.
By following these maintenance tips, you can help keep your lawn mower coil in good working order and prevent premature failure.