How to Check Ignition Coil with Ohm Meter (Chainsaw Tune-Up Tips)

It was a crisp autumn morning, the kind that makes you glad to be alive and working outdoors. I remember the scent of damp earth and freshly cut wood hanging heavy in the air. I was deep in the back forty, wrestling with my old faithful chainsaw – a beast that had seen better days, much like myself, I sometimes joked. I was felling some seasoned oak, destined to become winter fuel for my wood-burning stove. But the darn thing just wouldn’t start reliably. One minute it was roaring like a caged lion, the next it was sputtering and dying like a deflated balloon.

I fiddled with the carburetor, checked the fuel lines, even replaced the spark plug, but nothing seemed to solve the problem. Frustration was mounting faster than the woodpile. Then, a seasoned old logger, a fella named Earl, ambled over. He took one look at my exasperated face and the recalcitrant chainsaw and said, “Sounds like your ignition coil might be playing possum, son.”

The ignition coil? I’d heard the term, but never really understood what it did, let alone how to check it. Earl, with the patience of a saint and the wisdom of a man who’d spent his life in the woods, showed me how to use an ohm meter to diagnose the problem. Turns out, he was right. The ignition coil was shot. After replacing it, the chainsaw roared back to life, and I was back in business.

That day, I learned a valuable lesson: Knowing how to troubleshoot your chainsaw’s ignition system can save you time, money, and a whole lot of frustration. And that’s exactly what I want to share with you today. So, grab your ohm meter, and let’s dive into the world of chainsaw ignition coils!

What is an Ignition Coil and Why Does It Matter?

The ignition coil is a critical component of your chainsaw’s ignition system. Its primary function is to transform the low-voltage electricity from the magneto into a high-voltage spark that ignites the air-fuel mixture in the cylinder. Without a functioning ignition coil, your chainsaw simply won’t start or run properly.

Think of it like this: the ignition coil is the heart of your chainsaw’s electrical system. If it’s not pumping out the right voltage, the engine won’t get the spark it needs to run.

Here are some key reasons why the ignition coil is so important:

• Reliable Starting: A healthy ignition coil ensures a strong, consistent spark, making your chainsaw easier to start, especially in cold weather.
• Smooth Performance: A properly functioning ignition coil contributes to smoother engine operation, reducing misfires and improving overall performance.
• Fuel Efficiency: A strong spark promotes more complete combustion, leading to better fuel efficiency and reduced emissions.
• Engine Longevity: Misfires caused by a weak ignition coil can put extra stress on engine components, potentially shortening their lifespan.

Understanding the Chainsaw Ignition System

Before we dive into testing the ignition coil, let’s take a quick look at the chainsaw ignition system as a whole. This will give you a better understanding of how the ignition coil fits into the bigger picture.

The typical chainsaw ignition system consists of the following components:

• Magneto: The magneto is a small generator that produces electricity as the flywheel rotates.
• Ignition Coil: The ignition coil steps up the voltage from the magneto to create a spark.
• Spark Plug: The spark plug delivers the high-voltage spark to the combustion chamber, igniting the air-fuel mixture.
• Spark Plug Wire: The spark plug wire connects the ignition coil to the spark plug.
• Kill Switch: The kill switch allows you to ground the ignition system, stopping the engine.

Here’s how the system works:

1. As the flywheel rotates, it generates electricity in the magneto.
2. The magneto sends a low-voltage current to the ignition coil.
3. The ignition coil transforms the low-voltage current into a high-voltage spark.
4. The high-voltage spark travels through the spark plug wire to the spark plug.
5. The spark plug creates a spark in the combustion chamber, igniting the air-fuel mixture.

Symptoms of a Failing Ignition Coil

A failing ignition coil can manifest in a variety of ways. Recognizing these symptoms early can help you diagnose the problem and prevent further damage to your chainsaw.

Here are some common symptoms of a failing ignition coil:

• Difficult Starting: The chainsaw may be hard to start, especially when cold. You might have to pull the starter cord repeatedly before the engine fires.
• Intermittent Starting: The chainsaw may start sometimes, but not others. This can be frustrating and unpredictable.
• Rough Running: The engine may run roughly, with misfires and a lack of power. It might sound like it’s struggling to keep running.
• Stalling: The chainsaw may stall frequently, especially when under load. This can be dangerous, especially when you’re working in a remote location.
• No Spark: In the worst-case scenario, the ignition coil may fail completely, resulting in no spark at all.

If you experience any of these symptoms, it’s a good idea to check your ignition coil. I remember one time, I was cutting some firewood deep in the woods when my chainsaw suddenly started stalling every few minutes. It was a real pain, and it took me a while to figure out it was the ignition coil acting up.

Safety First: Important Precautions Before Testing

Before you start testing your ignition coil, it’s essential to take some safety precautions. Working with electrical components can be dangerous if you’re not careful.

Here are some important safety tips to keep in mind:

• Disconnect the Spark Plug Wire: Always disconnect the spark plug wire from the spark plug before working on the ignition system. This will prevent accidental shocks.
• Wear Gloves: Wear insulated gloves to protect your hands from electrical shock.
• Work in a Well-Ventilated Area: Work in a well-ventilated area to avoid inhaling fumes from gasoline or other chemicals.
• Avoid Wet Conditions: Do not work on the ignition system in wet conditions. Water can conduct electricity and increase the risk of shock.
• Read Your Owner’s Manual: Consult your chainsaw’s owner’s manual for specific safety instructions and recommendations.

Tools and Materials You’ll Need

To check your ignition coil with an ohm meter, you’ll need the following tools and materials:

• Ohm Meter (Multimeter): An ohm meter is a device that measures electrical resistance. You’ll need one to check the resistance of the ignition coil windings.
• Screwdrivers: You’ll need screwdrivers to remove the chainsaw’s cover and access the ignition coil.
• Wrench: You may need a wrench to remove the spark plug.
• Clean Cloth: A clean cloth will be useful for wiping off any dirt or debris from the ignition coil.
• Owner’s Manual: Your chainsaw’s owner’s manual will provide valuable information about the ignition system and recommended resistance values.

I recommend investing in a good quality ohm meter. A cheap meter may not be accurate, which can lead to inaccurate readings and misdiagnosis.

Step-by-Step Guide: Checking the Ignition Coil with an Ohm Meter

Now that you have the tools and materials you need, let’s get started with the testing process. Here’s a step-by-step guide on how to check your ignition coil with an ohm meter:

Step 1: Prepare the Chainsaw

• Turn off the chainsaw and remove the spark plug wire from the spark plug.
• Remove the chainsaw’s cover to access the ignition coil. The location of the ignition coil will vary depending on the model of your chainsaw. Consult your owner’s manual for specific instructions.
• Clean the ignition coil with a clean cloth to remove any dirt or debris.

Step 2: Set Up the Ohm Meter

• Set the ohm meter to the lowest resistance setting (usually 200 ohms).
• Touch the two probes of the ohm meter together. The meter should read close to zero, indicating continuity. If it doesn’t, check the meter’s settings and batteries.

Step 3: Test the Primary Winding

• The primary winding is the low-voltage side of the ignition coil. It’s typically connected to the magneto.
• Locate the two terminals on the primary winding. These are usually small posts or connectors.
• Place one probe of the ohm meter on one terminal and the other probe on the other terminal.
• Record the resistance reading. The reading should fall within the range specified in your owner’s manual. A typical range for the primary winding is 0.5 to 2 ohms.

Step 4: Test the Secondary Winding

• The secondary winding is the high-voltage side of the ignition coil. It’s connected to the spark plug wire.
• Locate the terminal for the spark plug wire. This is usually a high-voltage post or connector.
• Place one probe of the ohm meter on the spark plug wire terminal and the other probe on the metal core of the ignition coil (or the engine ground).
• Record the resistance reading. The reading should fall within the range specified in your owner’s manual. A typical range for the secondary winding is 2,000 to 10,000 ohms.

Step 5: Interpret the Readings

• Correct Resistance: If both the primary and secondary windings show resistance readings within the specified range, the ignition coil is likely good.
• Zero Resistance: If either winding shows zero resistance, it indicates a short circuit. The ignition coil is likely bad.
• Infinite Resistance: If either winding shows infinite resistance, it indicates an open circuit. The ignition coil is likely bad.
• Resistance Outside the Range: If the resistance readings are outside the specified range, it indicates a problem with the ignition coil. It may be partially shorted or open.

Step 6: Visual Inspection

• Visually inspect the ignition coil for any signs of damage, such as cracks, burns, or corrosion.
• Check the spark plug wire for any cracks or damage.
• Make sure the ignition coil is properly grounded to the engine.

Understanding Ohm Meter Readings: A Deeper Dive

Interpreting the readings from your ohm meter is crucial for diagnosing ignition coil problems. Let’s take a closer look at what the different readings mean and how to interpret them:

• Low Resistance (Close to Zero Ohms): A low resistance reading indicates that there is a short circuit in the winding. This means that the electricity is flowing directly from one point to another without passing through the entire winding. A short circuit can be caused by damaged insulation or a physical break in the wire.
• High Resistance (Infinite Ohms): A high resistance reading indicates that there is an open circuit in the winding. This means that the electricity cannot flow through the winding at all. An open circuit can be caused by a broken wire or a loose connection.
• Resistance Within Specified Range: If the resistance reading falls within the range specified in your owner’s manual, it indicates that the winding is likely good. However, it’s important to note that this doesn’t guarantee that the ignition coil is functioning perfectly. It’s possible for an ignition coil to have a slightly weakened spark, even if the resistance readings are within the specified range.
• Resistance Slightly Outside Specified Range: If the resistance reading is slightly outside the specified range, it may indicate a minor problem with the winding. In some cases, the ignition coil may still function properly, but it’s a good idea to keep an eye on it and replace it if you experience any performance issues.

It’s important to consult your chainsaw’s owner’s manual for the specific resistance values for your model. The resistance values can vary depending on the manufacturer and the type of ignition coil.

Troubleshooting Common Ignition Coil Problems

If your ignition coil fails the ohm meter test, or if you suspect that it’s causing problems with your chainsaw’s performance, here are some common troubleshooting tips:

• Check the Air Gap: The air gap is the distance between the ignition coil and the flywheel. If the air gap is too large or too small, it can affect the strength of the spark. Consult your owner’s manual for the correct air gap setting. You can use a feeler gauge to adjust the air gap.
• Check the Spark Plug Wire: Inspect the spark plug wire for any cracks, damage, or loose connections. Replace the spark plug wire if necessary.
• Check the Spark Plug: A fouled or worn spark plug can also cause ignition problems. Remove the spark plug and inspect it for signs of damage or carbon buildup. Clean or replace the spark plug as needed. I’ve seen spark plugs so caked with carbon that they wouldn’t fire even with a perfectly good ignition coil.
• Check the Ground Connection: Make sure the ignition coil is properly grounded to the engine. A loose or corroded ground connection can prevent the ignition coil from functioning properly. Clean the ground connection and tighten the mounting bolts.
• Test with a Known Good Ignition Coil: If you have access to a known good ignition coil, try swapping it with your existing ignition coil. If the chainsaw starts and runs properly with the known good ignition coil, it confirms that the original ignition coil is bad.

Replacing the Ignition Coil: A Step-by-Step Guide

If you’ve determined that your ignition coil is bad, you’ll need to replace it. Here’s a step-by-step guide on how to replace the ignition coil on your chainsaw:

Step 1: Disconnect the Spark Plug Wire

• Turn off the chainsaw and remove the spark plug wire from the spark plug.

Step 2: Remove the Chainsaw’s Cover

• Remove the chainsaw’s cover to access the ignition coil. The location of the ignition coil will vary depending on the model of your chainsaw. Consult your owner’s manual for specific instructions.

Step 3: Disconnect the Wires

• Disconnect the wires from the ignition coil. There may be one or two wires connected to the ignition coil. Make a note of which wire goes where so you can reconnect them properly.

Step 4: Remove the Ignition Coil

• Remove the screws or bolts that hold the ignition coil in place.
• Carefully remove the ignition coil from the chainsaw.

Step 5: Install the New Ignition Coil

• Install the new ignition coil in the chainsaw.
• Tighten the screws or bolts that hold the ignition coil in place.
• Make sure the ignition coil is properly aligned with the flywheel.

Step 6: Reconnect the Wires

• Reconnect the wires to the ignition coil. Make sure you connect the wires to the correct terminals.

Step 7: Adjust the Air Gap

• Adjust the air gap between the ignition coil and the flywheel. Consult your owner’s manual for the correct air gap setting. You can use a feeler gauge to adjust the air gap.

Step 8: Reinstall the Chainsaw’s Cover

• Reinstall the chainsaw’s cover.

Step 9: Reconnect the Spark Plug Wire

• Reconnect the spark plug wire to the spark plug.

Step 10: Test the Chainsaw

• Start the chainsaw and test it to make sure it’s running properly.

I always recommend using OEM (Original Equipment Manufacturer) parts when replacing the ignition coil. Aftermarket parts may not be as reliable or durable as OEM parts.

Preventive Maintenance: Keeping Your Ignition Coil Healthy

Preventive maintenance is key to keeping your ignition coil healthy and extending its lifespan. Here are some tips for maintaining your ignition coil:

• Keep the Chainsaw Clean: Keep your chainsaw clean and free of dirt and debris. Dirt and debris can accumulate around the ignition coil and cause it to overheat.
• Check the Air Gap Regularly: Check the air gap between the ignition coil and the flywheel regularly. Adjust the air gap as needed.
• Use Fresh Fuel: Use fresh, high-quality fuel in your chainsaw. Old or contaminated fuel can cause engine problems that can put extra stress on the ignition coil.
• Store the Chainsaw Properly: Store your chainsaw in a dry, protected location when not in use. This will help prevent corrosion and damage to the ignition coil.
• Follow the Manufacturer’s Recommendations: Follow the manufacturer’s recommendations for maintenance and service. This will help ensure that your chainsaw is running properly and that the ignition coil is protected.

Cost Considerations: Repair vs. Replacement

When faced with a failing ignition coil, you might wonder whether to repair it or replace it. In most cases, replacing the ignition coil is the more practical and cost-effective option.

Here’s why:

• Complexity of Repair: Repairing an ignition coil is a complex and time-consuming process that requires specialized tools and knowledge. It’s not something that most homeowners can do themselves.
• Cost of Repair: The cost of repairing an ignition coil can often be as high as or higher than the cost of replacing it. This is because the repair typically involves disassembling the ignition coil, identifying the problem, and replacing the faulty components.
• Reliability of Repair: Even if you’re able to repair the ignition coil, there’s no guarantee that it will be as reliable as a new one. The repaired ignition coil may be more prone to failure in the future.
• Cost of Replacement: Replacing the ignition coil is a relatively simple and straightforward process that most homeowners can do themselves. The cost of a new ignition coil is typically reasonable, especially compared to the cost of repair.

In my experience, it’s almost always better to replace a failing ignition coil than to try to repair it. You’ll save time, money, and frustration in the long run.

Choosing the Right Replacement Ignition Coil

When replacing your ignition coil, it’s important to choose the right replacement. Here are some factors to consider:

• Compatibility: Make sure the replacement ignition coil is compatible with your chainsaw model. Consult your owner’s manual or a parts supplier to ensure that you’re getting the right part.
• OEM vs. Aftermarket: As I mentioned earlier, I recommend using OEM (Original Equipment Manufacturer) parts whenever possible. OEM parts are designed and manufactured to meet the specific requirements of your chainsaw. Aftermarket parts may be cheaper, but they may not be as reliable or durable.
• Warranty: Look for a replacement ignition coil that comes with a warranty. This will protect you in case the ignition coil fails prematurely.
• Price: Compare prices from different suppliers before making a purchase. You may be able to find a good deal online or at a local hardware store.

Case Study: Diagnosing a Chainsaw Starting Problem

Let me share a real-world example of how I used an ohm meter to diagnose a chainsaw starting problem. A friend of mine, a small-scale logger named Jake, called me one day complaining that his chainsaw wouldn’t start. He’d tried everything he could think of, but nothing seemed to work.

I went over to Jake’s place and took a look at his chainsaw. It was an older model, but it was usually reliable. I started by checking the spark plug. It looked clean and dry, but I decided to replace it anyway, just to be sure. Still no luck.

Next, I checked the fuel lines and the carburetor. Everything seemed to be in order. I was starting to suspect that the problem might be with the ignition system.

I grabbed my ohm meter and started testing the ignition coil. The primary winding showed a resistance reading within the specified range, but the secondary winding showed infinite resistance. This indicated that there was an open circuit in the secondary winding.

I told Jake that his ignition coil was bad and needed to be replaced. He was a bit skeptical, but he trusted my judgment. We ordered a new ignition coil online and installed it a few days later.

Sure enough, the chainsaw started right up after we installed the new ignition coil. Jake was thrilled, and he thanked me for saving him a lot of time and frustration.

This case study illustrates the importance of knowing how to use an ohm meter to diagnose chainsaw problems. It can save you a lot of time and money in the long run.

Conclusion: Mastering Chainsaw Tune-Up with Ohm Meter Skills

Learning how to check your ignition coil with an ohm meter is a valuable skill for any chainsaw owner. It can help you diagnose problems quickly and easily, saving you time, money, and frustration. By understanding the function of the ignition coil, recognizing the symptoms of a failing coil, and mastering the use of an ohm meter, you can keep your chainsaw running smoothly for years to come.

Remember Earl, the old logger who taught me the ropes? He always said, “A little knowledge goes a long way, son. Especially when you’re out in the woods.” And he was right. Taking the time to learn about your chainsaw’s ignition system and how to troubleshoot it can make all the difference between a productive day and a frustrating one. So, keep practicing, keep learning, and keep your chainsaw roaring!

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