How to Check a Coil with Multimeter (Chainsaw Ignition Fix Tips)
In the rugged landscapes of the Pacific Northwest, where towering Douglas firs dominate the skyline, or in the frosty heart of Scandinavia where birch and pine are king, the need for reliable firewood and efficient wood processing is more than just a convenience—it’s a way of life. From the Appalachian mountains to the vast Siberian forests, people depend on the warmth of wood to get through harsh winters. And at the heart of this tradition, often lies a trusty chainsaw.
But what happens when your chainsaw, the lifeline of your wood-fueled existence, sputters and dies? More often than not, the culprit is a faulty ignition coil. That’s why I’m here to guide you through a crucial troubleshooting step: checking the coil with a multimeter. This skill can save you time, money, and a whole lot of frustration.
How to Check a Coil with Multimeter (Chainsaw Ignition Fix Tips)
Let’s face it. A dead chainsaw during the height of firewood season is more than just an inconvenience; it’s a genuine crisis. I’ve been there, staring at a pile of logs with a lifeless saw in my hands, the biting wind nipping at my face. The good news is that many chainsaw problems are simple to diagnose and fix yourself. One of the most common issues? A faulty ignition coil. With a multimeter and a little know-how, you can quickly determine if the coil is the problem and avoid an unnecessary trip to the repair shop.
Why the Ignition Coil Matters
The ignition coil is a vital component of your chainsaw’s ignition system. It takes the low-voltage current from the magneto (or battery, in some cases) and transforms it into the high-voltage jolt needed to create a spark at the spark plug. This spark ignites the fuel-air mixture in the cylinder, starting the engine. Without a functioning coil, your chainsaw is essentially a very heavy, very noisy paperweight.
Gathering Your Tools and Preparing for the Test
Before we dive into the testing process, let’s make sure you have everything you need. This is a straightforward process, but having the right tools and taking the proper precautions will ensure you get accurate results and stay safe.
- A Multimeter: This is the heart of our operation. A digital multimeter is preferred for its accuracy and ease of use, but an analog multimeter will also work. Make sure it’s set to measure resistance (Ohms – Ω).
- Screwdrivers: You’ll likely need a screwdriver to access the ignition coil. Have a variety of sizes and types (Phillips and flathead) on hand.
- Wrench or Socket Set: Depending on your chainsaw model, you might need a wrench or socket to remove the coil.
- Safety Glasses: Always protect your eyes when working with tools and machinery.
- Work Gloves: Protect your hands from sharp edges and potential electrical shocks.
- Your Chainsaw’s Manual: This is invaluable for locating the ignition coil and understanding any specific instructions for your model.
- A Notebook and Pen: To record your readings and observations. Trust me, you’ll want to keep track of the numbers.
Safety First!
- Disconnect the Spark Plug: Remove the spark plug wire from the spark plug before you start any work on the ignition system. This prevents accidental starting.
- Let the Engine Cool: If you’ve been using the chainsaw recently, let the engine cool down completely before you start working on it.
- Work in a Well-Ventilated Area: If you need to start the chainsaw for any reason, do it in a well-ventilated area to avoid inhaling exhaust fumes.
Locating the Ignition Coil
The location of the ignition coil can vary depending on your chainsaw model, but it’s usually found near the flywheel. Consult your chainsaw’s manual for the exact location.
Typically, you’ll need to remove an engine cover or two to gain access to the coil. This usually involves unscrewing a few screws or bolts. Take your time and be careful not to force anything. If something doesn’t seem right, double-check the manual.
Once you’ve removed the necessary covers, you should see the ignition coil. It’s usually a small, rectangular component with wires leading to the spark plug and the engine.
Understanding Resistance and Continuity
Before we start testing, let’s quickly review what we’re measuring. The multimeter will measure the resistance of the coil, which is the opposition to the flow of electrical current. Resistance is measured in ohms (Ω). A good coil will have a specific resistance range, while a bad coil will have either very high resistance (an open circuit) or very low resistance (a short circuit).
Continuity, on the other hand, is a measure of whether a circuit is complete. If there is continuity, the circuit is complete and electricity can flow. If there is no continuity, the circuit is broken.
Testing the Primary Winding
The primary winding is the low-voltage side of the coil. It’s connected to the magneto (or battery) and receives the initial electrical current.
- Set Your Multimeter: Set your multimeter to measure resistance (Ohms – Ω) on a low range (e.g., 200Ω).
- Connect the Probes: Place one probe of the multimeter on the primary terminal of the coil (usually a small metal tab or connector) and the other probe on the engine ground (any clean, unpainted metal part of the engine).
- Read the Resistance: Observe the reading on the multimeter. The resistance should be within the range specified in your chainsaw’s manual. Typically, it will be a very low resistance, often less than 1 ohm.
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Interpret the Results:
- Low Resistance (close to 0 ohms): This is usually a good sign. It indicates that the primary winding is intact and electricity can flow through it.
- High Resistance (infinite or very high ohms): This indicates an open circuit in the primary winding. The coil is likely faulty and needs to be replaced.
- Zero Resistance (a direct short): This indicates a short circuit in the primary winding. The coil is definitely faulty and needs to be replaced.
Testing the Secondary Winding
The secondary winding is the high-voltage side of the coil. It’s connected to the spark plug and delivers the high-voltage jolt needed to create a spark.
- Set Your Multimeter: Set your multimeter to measure resistance (Ohms – Ω) on a higher range (e.g., 20kΩ or 200kΩ).
- Connect the Probes: Place one probe of the multimeter on the spark plug wire terminal of the coil and the other probe on the engine ground.
- Read the Resistance: Observe the reading on the multimeter. The resistance should be within the range specified in your chainsaw’s manual. Typically, it will be a higher resistance than the primary winding, often between 2kΩ and 10kΩ.
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Interpret the Results:
- Resistance within Range: This is a good sign. It indicates that the secondary winding is intact and capable of producing the high-voltage spark.
- High Resistance (infinite or very high ohms): This indicates an open circuit in the secondary winding. The coil is likely faulty and needs to be replaced.
- Low Resistance (close to 0 ohms): This indicates a short circuit in the secondary winding. The coil is definitely faulty and needs to be replaced.
Testing for Continuity
In addition to measuring resistance, you can also test for continuity between the coil terminals and the engine ground. This can help you identify shorts or open circuits that might not be apparent from the resistance measurements alone.
- Set Your Multimeter: Set your multimeter to the continuity testing mode (usually indicated by a diode symbol or a speaker symbol).
- Connect the Probes: Place one probe of the multimeter on a coil terminal (either the primary or secondary) and the other probe on the engine ground.
- Listen for the Beep: If the multimeter beeps, it indicates that there is continuity between the terminal and the ground, which means there is a short circuit. If the multimeter doesn’t beep, it indicates that there is no continuity, which is what you want.
- Repeat for All Terminals: Repeat this test for all terminals of the coil to ensure that there are no shorts to ground.
Interpreting the Results: When to Replace the Coil
Based on the resistance and continuity tests, you can determine whether the ignition coil is functioning properly or needs to be replaced.
- Good Coil: If the resistance values for both the primary and secondary windings are within the specified range, and there is no continuity between any of the terminals and the engine ground, the coil is likely good.
- Bad Coil: If the resistance values for either the primary or secondary windings are outside the specified range, or there is continuity between any of the terminals and the engine ground, the coil is likely bad and needs to be replaced.
Other Potential Issues
Even if the ignition coil tests good, there are other potential issues that could be causing your chainsaw to not start. Here are a few things to check:
- Spark Plug: A fouled or damaged spark plug can prevent the engine from starting. Remove the spark plug and inspect it. If it’s dirty or damaged, clean it or replace it.
- Spark Plug Wire: A damaged spark plug wire can also prevent the engine from starting. Inspect the wire for cracks or breaks. If it’s damaged, replace it.
- Fuel System: A clogged fuel filter, a blocked fuel line, or a faulty carburetor can also prevent the engine from starting. Inspect the fuel system and clean or replace any clogged or damaged components.
- Air Filter: A clogged air filter can restrict airflow to the engine and prevent it from starting. Inspect the air filter and clean or replace it.
- Flywheel Key: The flywheel key is a small metal piece that connects the flywheel to the crankshaft. If the flywheel key is sheared, it can cause the timing to be off and prevent the engine from starting. Inspect the flywheel key and replace it if it’s sheared.
- Low Compression: Low compression can also prevent the engine from starting. A compression test can help you determine if the engine has low compression.
Replacing the Ignition Coil
If you’ve determined that the ignition coil is faulty, the next step is to replace it. This is a relatively straightforward process, but it’s important to follow the instructions in your chainsaw’s manual.
- Disconnect the Spark Plug Wire: Remove the spark plug wire from the spark plug.
- Remove the Old Coil: Unscrew the screws or bolts that hold the coil in place. Disconnect the wires from the coil.
- Install the New Coil: Connect the wires to the new coil. Screw the screws or bolts that hold the coil in place.
- Set the Air Gap: The air gap is the distance between the coil and the flywheel. This is a critical setting that affects the performance of the ignition system. Consult your chainsaw’s manual for the correct air gap setting. You can use a business card or a feeler gauge to set the air gap.
- Reconnect the Spark Plug Wire: Reconnect the spark plug wire to the spark plug.
Setting the Air Gap: A Critical Detail
The air gap is the distance between the ignition coil and the flywheel. This gap is crucial because it affects the strength of the magnetic field that induces voltage in the coil. Too large of a gap, and the spark will be weak or nonexistent. Too small, and the coil can rub against the flywheel, causing damage.
Your chainsaw’s manual will specify the correct air gap, typically measured in thousandths of an inch (e.g., 0.010″ or 0.012″). Here’s how to set it:
- Loosen the Coil: Loosen the screws that hold the coil in place, but don’t remove them completely. You want to be able to move the coil slightly.
- Insert the Spacer: Use a business card, a piece of cardboard, or a feeler gauge of the correct thickness as a spacer between the coil and the flywheel.
- Tighten the Coil: Gently push the coil against the spacer and tighten the screws.
- Remove the Spacer: Remove the spacer. The air gap is now set.
Case Study: The Case of the Stubborn Stihl
I remember a few years back, a friend of mine, let’s call him Dave, was having trouble with his Stihl MS 290. He’d been cutting firewood all day, and suddenly, the saw just died. He tried everything he could think of – checked the fuel, cleaned the air filter, even replaced the spark plug – but nothing worked.
Finally, he called me, frustrated and ready to throw in the towel. I told him to bring the saw over, and we’d take a look. After a quick inspection, I suspected the ignition coil. We followed the steps I’ve outlined above, and sure enough, the secondary winding showed infinite resistance. The coil was dead as a doornail.
We replaced the coil, set the air gap, and on the first pull, the saw roared back to life. Dave was ecstatic. He’d been ready to give up and take the saw to a repair shop, but with a little troubleshooting and a new coil, he was back in business.
The interesting thing about Dave’s case was that the coil had failed suddenly, without any warning signs. This is not uncommon. Ignition coils can fail due to heat, vibration, or simply old age. That’s why it’s a good idea to check the coil periodically, especially if you’re experiencing starting problems.
The Importance of Using Quality Replacement Parts
When replacing the ignition coil, it’s tempting to save a few bucks by buying a cheap aftermarket part. However, I strongly recommend using a high-quality replacement coil from a reputable manufacturer.
Cheap coils are often made with inferior materials and may not meet the specifications of the original part. This can lead to poor performance, premature failure, and even damage to your chainsaw.
A high-quality coil, on the other hand, will be built to last and will provide reliable performance for years to come. It’s worth the extra investment in the long run.
Preventative Maintenance: Keeping Your Chainsaw Healthy
The best way to avoid ignition coil problems is to perform regular preventative maintenance on your chainsaw. Here are a few tips:
- Keep the Engine Clean: Dirt and debris can build up around the engine and cause it to overheat. Clean the engine regularly with a brush and compressed air.
- Use Fresh Fuel: Old fuel can gum up the carburetor and cause starting problems. Use fresh fuel and add a fuel stabilizer to prevent it from going bad.
- Maintain the Air Filter: A clogged air filter can restrict airflow to the engine and cause it to overheat. Clean or replace the air filter regularly.
- Inspect the Spark Plug: A fouled or damaged spark plug can prevent the engine from starting. Inspect the spark plug regularly and clean or replace it.
- Store the Chainsaw Properly: When you’re not using the chainsaw, store it in a clean, dry place. Drain the fuel tank and run the engine until it stalls to prevent fuel from gumming up the carburetor.
Understanding Wood Species and Their Impact on Chainsaw Wear
The type of wood you’re cutting can also affect the wear and tear on your chainsaw, including the ignition system. Hardwoods like oak and maple are much denser than softwoods like pine and fir. Cutting hardwoods requires more power and puts more strain on the engine, which can lead to overheating and premature failure of components like the ignition coil.
Here’s a quick breakdown of common wood species and their impact on chainsaw wear:
- Softwoods (Pine, Fir, Spruce): Easier to cut, less strain on the engine, less wear and tear on the chainsaw.
- Medium-Hardwoods (Birch, Alder, Cherry): Moderate cutting effort, moderate strain on the engine, moderate wear and tear on the chainsaw.
- Hardwoods (Oak, Maple, Hickory): Difficult to cut, high strain on the engine, high wear and tear on the chainsaw.
If you’re primarily cutting hardwoods, it’s important to use a chainsaw that is designed for heavy-duty use and to perform regular maintenance to prevent problems.
Chainsaw Safety: A Constant Priority
No discussion about chainsaw maintenance is complete without emphasizing safety. Chainsaws are powerful tools that can cause serious injury if not used properly. Here are a few safety tips to keep in mind:
- Wear Appropriate Safety Gear: Always wear safety glasses, hearing protection, gloves, and sturdy boots when operating a chainsaw.
- Use the Right Chainsaw for the Job: Don’t use a small chainsaw to fell large trees. Use a chainsaw that is appropriately sized for the task.
- Maintain a Safe Distance: Keep bystanders and pets away from the work area.
- Be Aware of Your Surroundings: Watch out for obstacles, such as rocks, roots, and branches.
- Use Proper Cutting Techniques: Avoid kickback by using proper cutting techniques.
- Take Breaks: Chainsaw work can be tiring. Take breaks to avoid fatigue.
- Never Operate a Chainsaw Under the Influence: Alcohol and drugs can impair your judgment and coordination.
Chainsaw Maintenance and Wood Processing Efficiency
Did you know that proper chainsaw maintenance can significantly impact your wood processing efficiency? A well-maintained chainsaw cuts faster, requires less effort, and produces cleaner cuts. This translates to more firewood processed in less time, with less fatigue.
Here are a few ways that chainsaw maintenance can improve your wood processing efficiency:
- Sharp Chain: A sharp chain cuts faster and requires less effort. Sharpen the chain regularly or replace it when it becomes dull.
- Clean Air Filter: A clean air filter allows the engine to breathe properly, which improves performance and fuel efficiency.
- Proper Lubrication: Proper lubrication reduces friction and wear on the engine and chain, which extends the life of the chainsaw and improves performance.
- Correct Air Gap: A properly set air gap ensures that the ignition system is functioning optimally, which improves starting and performance.
By keeping your chainsaw in top condition, you can maximize your wood processing efficiency and get more done in less time.
The Future of Wood Processing: Embracing Technology
The world of wood processing is constantly evolving, with new technologies and techniques emerging all the time. From robotic log splitters to automated firewood processors, the future of wood processing is looking increasingly automated and efficient.
While these technologies may seem out of reach for the average homeowner or small firewood producer, they offer a glimpse into the future of the industry. As these technologies become more affordable and accessible, they will likely play an increasingly important role in wood processing.
Now, go forth and conquer those logs! And remember, safety first!
