How to Test Ignition Coil with Ohm Meter (Chainsaw Tune-Up Tips)
Here’s Your Opportunity to Breathe New Life into Your Chainsaw!
Is your chainsaw sputtering, refusing to start, or just generally acting like it’s seen better days? Before you resign yourself to buying a brand-new saw, let me tell you, there’s a good chance the culprit is a faulty ignition coil. And the best part? You can diagnose this problem yourself with a simple tool: an ohmmeter.
I’ve spent years felling trees, bucking logs, and splitting firewood. I’ve seen it all, from vintage saws that refuse to quit to modern machines packed with technology. Through it all, I’ve learned that a little preventative maintenance goes a long way. And one of the most common issues I encounter, especially with older saws, is ignition problems.
In this guide, I’ll walk you through exactly how to test your chainsaw’s ignition coil using an ohmmeter. You’ll learn what readings to look for, what they mean, and what steps to take next. This isn’t just about fixing a saw; it’s about empowering you to understand your equipment, save money on repairs, and get back to the satisfying work of turning trees into usable wood.
I’ll share my experiences, offer insights into wood species and their impact on saw performance, and even touch on safety standards to keep you protected. So, grab your ohmmeter, and let’s dive in!
How to Test Ignition Coil with Ohm Meter (Chainsaw Tune-Up Tips)
An ignition coil is a critical component in your chainsaw’s ignition system. It takes the low voltage from the engine and steps it up to a high voltage, creating the spark at the spark plug that ignites the fuel-air mixture in the cylinder. A faulty ignition coil can lead to a no-start condition, weak spark, or intermittent engine performance. Using an ohmmeter is a simple and effective way to diagnose a potential problem.
Understanding the Importance of a Good Spark
Before we get into the nitty-gritty of testing, let’s talk about why a good spark is so important. Think of your chainsaw’s engine like a tiny controlled explosion. That explosion is what drives the piston, which in turn spins the chain. For that explosion to happen reliably, you need a consistent, strong spark at the right time.
A weak spark can lead to incomplete combustion, meaning you’re not getting the full power out of your fuel. This translates to a saw that struggles to cut through hardwoods or bogs down under load. It can also lead to increased fuel consumption and higher emissions.
I remember one time I was working on a particularly tough batch of oak. My saw was running, but it was laboring hard, and I could smell unburnt fuel. After checking the usual suspects (air filter, fuel filter), I tested the ignition coil and found it was producing a weak spark. Replacing it made a world of difference. The saw ran smoother, cut faster, and didn’t leave me feeling like I’d just run a marathon after a couple of hours.
What is an Ohmmeter and How Does It Work?
An ohmmeter is a device used to measure electrical resistance. Resistance is the opposition to the flow of electrical current. It’s measured in ohms (Ω). An ohmmeter works by applying a small voltage to a circuit and measuring the current that flows. The resistance is then calculated using Ohm’s Law (Resistance = Voltage / Current).
Think of it like water flowing through a pipe. Resistance is like a constriction in the pipe. The wider the constriction, the less water can flow. Similarly, the higher the resistance in an electrical circuit, the less current can flow.
In the context of an ignition coil, the ohmmeter helps us determine if the coil’s windings are intact and providing the correct amount of resistance. A shorted or open winding will result in an incorrect resistance reading, indicating a faulty coil.
Safety First: Disconnecting and Grounding
Before you start poking around with an ohmmeter, safety is paramount.
- Disconnect the Spark Plug: Remove the spark plug wire from the spark plug. This prevents accidental starting of the engine.
- Ground the Spark Plug Wire: Ground the spark plug wire to the engine block. This discharges any residual voltage in the ignition system. You can do this by inserting a spare spark plug into the wire boot and touching the plug’s metal body to the engine.
- Turn Off the Chainsaw: Ensure the chainsaw’s power switch is in the “OFF” position.
- Wear Gloves: Consider wearing insulated gloves to provide an extra layer of protection.
I’ve always made it a habit to double-check that the spark plug is disconnected and grounded before working on any ignition system. It’s a simple step that can prevent a nasty shock.
Gathering Your Tools and Materials
Here’s what you’ll need for this project:
- Ohmmeter (Multimeter): A digital multimeter is ideal, but an analog meter will also work.
- Screwdrivers: You’ll likely need a screwdriver to access the ignition coil.
- Wrench (if needed): Some coils are held in place with bolts.
- Chainsaw Repair Manual (Optional): Your manual will provide specific resistance values for your model. If you don’t have a manual, you can often find one online.
- Clean Rags: To wipe down the coil and terminals.
- Wire Brush (Optional): To clean corroded terminals.
Step-by-Step Guide: Testing the Ignition Coil
Here’s the meat of the matter – how to actually test the coil.
Step 1: Locating the Ignition Coil
The ignition coil is typically located near the flywheel of the engine. It’s a small, rectangular component with two or more terminals. It might be covered by a plastic housing or shield. Consult your chainsaw’s repair manual for the exact location.
Step 2: Visual Inspection
Before you start testing with the ohmmeter, give the ignition coil a thorough visual inspection. Look for:
- Cracks or Damage: Cracks in the coil’s housing can allow moisture to enter, leading to shorts and malfunctions.
- Corrosion: Check the terminals for corrosion. Corrosion can increase resistance and prevent proper spark.
- Loose Wires: Make sure all wires connected to the coil are securely attached.
- Burn Marks: Burn marks can indicate overheating and internal damage.
If you see any of these issues, there’s a good chance the coil is faulty and needs to be replaced.
Step 3: Setting Up Your Ohmmeter
- Turn on the Ohmmeter: Turn on your multimeter and set it to measure resistance (ohms – Ω). You’ll typically see a symbol that looks like the Greek letter omega (Ω).
- Select the Appropriate Range: If your ohmmeter has multiple ranges, start with the lowest range (e.g., 200 ohms) and increase it as needed. Some digital multimeters have an auto-ranging feature, which automatically selects the correct range.
- Zero the Meter (Analog Meters): If you’re using an analog ohmmeter, you’ll need to zero the meter before taking a reading. Touch the two probes together and adjust the “zero adjust” knob until the needle points to zero ohms. Digital multimeters don’t require this step.
Step 4: Testing the Primary Winding
The primary winding is the low-voltage side of the ignition coil. It’s typically connected to the ignition module or points.
- Identify the Primary Terminals: Consult your chainsaw’s repair manual or look for markings on the coil itself. The primary terminals are usually smaller than the secondary terminal.
- Connect the Probes: Place one ohmmeter probe on one primary terminal and the other probe on the other primary terminal.
- Read the Resistance: Note the resistance reading on the ohmmeter. The resistance should be within the range specified in your chainsaw’s repair manual.
Expected Primary Winding Resistance:
- Generally, the primary winding resistance should be very low, typically between 0.5 and 5 ohms. However, this value can vary depending on the make and model of your chainsaw.
Step 5: Testing the Secondary Winding
The secondary winding is the high-voltage side of the ignition coil. It’s connected to the spark plug wire.
- Identify the Secondary Terminal: The secondary terminal is usually a single terminal or a high-tension lead that connects directly to the spark plug wire.
- Connect the Probes: Place one ohmmeter probe on the secondary terminal and the other probe on the engine ground (e.g., a clean, unpainted metal surface on the engine block).
- Read the Resistance: Note the resistance reading on the ohmmeter. The resistance should be within the range specified in your chainsaw’s repair manual.
Expected Secondary Winding Resistance:
- The secondary winding resistance is typically much higher than the primary winding resistance, usually ranging from 2,000 to 15,000 ohms (2 kΩ to 15 kΩ). Again, this value can vary, so consult your manual.
Step 6: Interpreting the Results
Here’s how to interpret the resistance readings you obtained:
- Correct Resistance: If the resistance readings for both the primary and secondary windings are within the specified range, the ignition coil is likely good.
- Zero Resistance (Short Circuit): A reading of zero ohms indicates a short circuit in the winding. This means the wire insulation has broken down, and the current is flowing directly from one point to another without going through the entire winding. The coil is faulty and needs to be replaced.
- Infinite Resistance (Open Circuit): A reading of infinite resistance (often displayed as “OL” or “1” on a digital multimeter) indicates an open circuit in the winding. This means the wire is broken, and current cannot flow through the winding. The coil is faulty and needs to be replaced.
- Resistance Outside of Specified Range: If the resistance reading is higher or lower than the specified range, it indicates a problem with the winding. The coil may be partially shorted or have increased resistance due to corrosion or damage. The coil may be faulty and should be tested further or replaced.
Example Scenarios:
- Scenario 1: You test the primary winding and get a reading of 0.8 ohms. You test the secondary winding and get a reading of 8,000 ohms. Your chainsaw’s repair manual specifies a primary winding resistance of 0.5-1.5 ohms and a secondary winding resistance of 5,000-10,000 ohms. In this case, the ignition coil is likely good.
- Scenario 2: You test the primary winding and get a reading of 0 ohms. You test the secondary winding and get a reading of 10,000 ohms. In this case, the primary winding is shorted, and the ignition coil needs to be replaced.
- Scenario 3: You test the primary winding and get a reading of 1 ohm. You test the secondary winding and get a reading of “OL” (overload). In this case, the secondary winding is open, and the ignition coil needs to be replaced.
Advanced Troubleshooting Tips
Testing the ignition coil with an ohmmeter is a good starting point, but it’s not always definitive. Here are some additional troubleshooting tips:
- Spark Test: The most reliable way to confirm a faulty ignition coil is to perform a spark test. Reconnect the spark plug wire to the spark plug. Hold the spark plug against the engine block (making sure the metal part of the spark plug is touching the metal of the engine). Pull the starter cord. You should see a bright blue spark jump across the spark plug gap. A weak, yellow spark, or no spark at all, indicates a problem with the ignition system.
- Check the Air Gap: The air gap is the distance between the ignition coil and the flywheel. An incorrect air gap can prevent the coil from generating a strong spark. Consult your chainsaw’s repair manual for the correct air gap specification. You’ll typically need a feeler gauge to adjust the air gap properly.
- Inspect the Flywheel Magnet: The flywheel magnet generates the electrical current that charges the ignition coil. If the magnet is weak or damaged, it won’t be able to charge the coil properly. You can test the magnet by holding a screwdriver near it. The screwdriver should be strongly attracted to the magnet.
- Check the Wiring: Inspect all wires connected to the ignition coil and the ignition module for damage, corrosion, or loose connections.
- Test the Ignition Module (if applicable): Some chainsaws use an ignition module instead of traditional points and condenser. The ignition module controls the timing and duration of the spark. If you suspect a problem with the ignition module, consult your chainsaw’s repair manual for testing procedures.
The Importance of Proper Spark Plug Maintenance
While we’re on the subject of ignition, let’s not forget the unsung hero of the combustion process: the spark plug. A fouled, worn, or improperly gapped spark plug can wreak havoc on your chainsaw’s performance, even if the ignition coil is in perfect working order.
I’ve seen countless instances where a seemingly mysterious engine problem was traced back to a simple spark plug issue. Carbon buildup, oil fouling, or a widened gap can all prevent the spark plug from igniting the fuel-air mixture efficiently.
Here are a few tips for proper spark plug maintenance:
- Regular Cleaning: Clean the spark plug electrodes regularly with a wire brush to remove carbon deposits.
- Gap Adjustment: Check and adjust the spark plug gap according to your chainsaw’s specifications. Use a spark plug gap tool to ensure the correct gap.
- Replacement: Replace the spark plug at the recommended intervals (typically every 50-100 hours of use).
- Proper Spark Plug Type: Ensure you’re using the correct spark plug type for your chainsaw. Using the wrong spark plug can lead to poor performance or even engine damage.
Wood Species and Their Impact on Chainsaw Performance
Speaking of performance, let’s briefly touch on how different wood species can affect your chainsaw’s operation. Hardwoods like oak, maple, and hickory are denser and require more power to cut than softwoods like pine, fir, and cedar.
When cutting hardwoods, it’s crucial to ensure your chainsaw is properly tuned and that the chain is sharp. A dull chain or a weak ignition system will make cutting hardwoods a frustrating and time-consuming experience.
I’ve found that hardwoods also tend to dull chains faster than softwoods. The higher density and abrasive nature of hardwoods can wear down the cutting edges of the chain teeth more quickly. Therefore, it’s essential to sharpen your chain more frequently when working with hardwoods.
Choosing the Right Chainsaw for the Job
Of course, the best way to ensure optimal performance is to choose the right chainsaw for the job. A small, lightweight chainsaw might be suitable for limbing and pruning, but it won’t be adequate for felling large trees or bucking hardwoods.
Consider the following factors when choosing a chainsaw:
- Engine Size: A larger engine will provide more power for cutting hardwoods and larger trees.
- Bar Length: The bar length should be appropriate for the size of the trees you’ll be cutting.
- Weight: A lighter chainsaw will be easier to handle and maneuver, especially for extended periods.
- Features: Look for features like anti-vibration systems, chain brakes, and easy-start systems to improve comfort and safety.
Common Chainsaw Problems and Solutions
Beyond ignition coil issues, here are some other common chainsaw problems and their potential solutions:
- Chainsaw Won’t Start:
- Possible Causes: Empty fuel tank, stale fuel, clogged fuel filter, clogged air filter, fouled spark plug, faulty ignition coil, low compression.
- Solutions: Fill the fuel tank with fresh fuel, replace the fuel filter, clean or replace the air filter, clean or replace the spark plug, test the ignition coil, check the engine compression.
- Chainsaw Starts But Stalls:
- Possible Causes: Clogged fuel filter, clogged air filter, incorrect carburetor settings, vacuum leak, faulty ignition coil.
- Solutions: Replace the fuel filter, clean or replace the air filter, adjust the carburetor settings, check for vacuum leaks, test the ignition coil.
- Chainsaw Runs Poorly:
- Possible Causes: Clogged fuel filter, clogged air filter, incorrect carburetor settings, dull chain, worn piston rings.
- Solutions: Replace the fuel filter, clean or replace the air filter, adjust the carburetor settings, sharpen the chain, check the engine compression.
- Chainsaw Chain Won’t Oil:
- Possible Causes: Empty oil tank, clogged oil filter, clogged oiler, faulty oil pump.
- Solutions: Fill the oil tank, replace the oil filter, clean the oiler, check the oil pump.
Cost-Effectiveness of DIY Chainsaw Repair
One of the biggest benefits of learning how to diagnose and repair your own chainsaw is the cost savings. Chainsaw repair shops can charge a significant amount for labor, especially for complex repairs. By performing simple tasks like testing the ignition coil and replacing the spark plug yourself, you can save a considerable amount of money.
I’ve saved hundreds, if not thousands, of dollars over the years by doing my own chainsaw maintenance and repairs. Not only that, but I’ve also gained a deeper understanding of how my equipment works, which allows me to identify and address potential problems before they become major issues.
Safety Standards and Best Practices
Working with chainsaws can be dangerous, so it’s essential to follow safety standards and best practices. Here are a few key safety considerations:
- Wear Appropriate Safety Gear: Always wear safety glasses, hearing protection, gloves, chaps, and a helmet when operating a chainsaw.
- Inspect Your Chainsaw Before Use: Before each use, inspect your chainsaw for any signs of damage or wear. Check the chain tension, oil level, and fuel level.
- Maintain a Safe Working Distance: Keep a safe distance from other people and obstacles when operating a chainsaw.
- Use Proper Cutting Techniques: Use proper cutting techniques to avoid kickback and other hazards.
- Never Cut Above Your Head: Never cut above your head, as this can increase the risk of losing control of the chainsaw.
- Be Aware of Your Surroundings: Be aware of your surroundings and watch out for hazards like falling branches and uneven terrain.
- Take Breaks: Take frequent breaks to avoid fatigue, which can increase the risk of accidents.
- Store Your Chainsaw Safely: Store your chainsaw in a safe location where it won’t be accessible to children or unauthorized users.
The Global Perspective: Challenges Faced by Chainsaw Users
The challenges faced by chainsaw users vary depending on their location and circumstances. In some parts of the world, access to reliable equipment and spare parts can be limited. In other areas, environmental regulations and safety standards may be less stringent.
Small logging operations and firewood producers often face unique challenges, such as limited access to capital, fluctuating market prices, and the need to compete with larger, more established companies.
By sharing knowledge and best practices, we can help chainsaw users around the world overcome these challenges and operate safely and efficiently.
Conclusion: Empowering Yourself with Chainsaw Knowledge
Testing your chainsaw’s ignition coil with an ohmmeter is a valuable skill that can save you time, money, and frustration. By understanding the basics of ignition systems and following the steps outlined in this guide, you can diagnose and repair a common chainsaw problem yourself.
Remember, safety should always be your top priority. Wear appropriate safety gear, follow proper cutting techniques, and be aware of your surroundings.
With a little knowledge and practice, you can become a more confident and capable chainsaw user, able to tackle a wide range of wood processing tasks safely and efficiently. So, get out there, get your hands dirty, and enjoy the satisfaction of working with wood!
