How to Check Ignition Coil Pack with Multimeter (Chainsaw Pro Tips)
“Give me six hours to chop down a tree and I will spend the first four sharpening the axe.” – Abraham Lincoln
As someone deeply entrenched in the world of wood, from felling trees to splitting firewood, I’ve learned that a sharp axe – or, in our modern context, a well-maintained chainsaw – is paramount. But even the sharpest chain is useless if the engine sputters and dies. And more often than not, when a chainsaw refuses to cooperate, the ignition coil pack is the prime suspect.
So, how do you diagnose this crucial component? With a multimeter, of course! This guide, born from years of experience and countless troubleshooting sessions, will walk you through the process of checking your chainsaw’s ignition coil pack with a multimeter, turning you from a frustrated woodcutter into a confident chainsaw mechanic.
Why Your Chainsaw’s Ignition Coil Pack Matters
Before we dive into the nitty-gritty of testing, let’s understand why the ignition coil pack is so vital. Think of it as the heart of your chainsaw’s electrical system. It takes the low-voltage current from the stator (or alternator) and transforms it into the high-voltage spark needed to ignite the air-fuel mixture in the cylinder, creating the combustion that drives the piston and, ultimately, the chain.
A faulty ignition coil pack means no spark, no combustion, and no cutting. It’s as simple as that. Recognizing the symptoms of a failing coil pack can save you valuable time and effort.
Common Symptoms of a Faulty Ignition Coil Pack
- Hard Starting: The engine cranks but refuses to fire up. This is often the first sign of a weakening coil.
- Intermittent Stalling: The chainsaw runs for a while, then suddenly dies, especially when it gets hot. This is a classic symptom of a coil pack breaking down under load.
- Weak Spark: The spark plug produces a weak or inconsistent spark, leading to poor performance.
- No Spark at All: The most obvious symptom – the spark plug produces absolutely no spark, rendering the chainsaw useless.
- Rough Running: The engine runs unevenly, misfires, and lacks power. This can be due to a coil pack that’s only partially functioning.
I remember one particularly frustrating day in the woods. I was deep into a logging project, felling some large oak trees for a custom woodworking client. My trusty Stihl MS 290, normally a workhorse, started sputtering and stalling after only a few cuts. I initially suspected a fuel issue, but after cleaning the carburetor and replacing the fuel filter, the problem persisted. It was only after checking the ignition coil pack with my multimeter that I discovered the culprit. The coil was producing a weak and intermittent spark, causing the engine to cut out. Replacing the coil pack solved the problem, and I was back to felling trees in no time.
Essential Tools for the Job
Before you start poking around with wires, make sure you have the right tools at your disposal. Safety first, always!
- Multimeter: A digital multimeter (DMM) is ideal for accurate readings, but an analog multimeter will also work. Make sure it can measure resistance (ohms) and voltage.
- Screwdrivers: You’ll need a variety of screwdrivers to remove covers and access the ignition coil pack.
- Spark Plug Wrench: To remove and inspect the spark plug.
- Feeler Gauge: To check and adjust the air gap between the ignition coil and the flywheel.
- Safety Glasses: Protect your eyes from debris.
- Gloves: Protect your hands from dirt and potential electrical shocks.
- Chainsaw Repair Manual: A repair manual specific to your chainsaw model can be invaluable for locating components and understanding wiring diagrams.
Safety First: Precautions Before You Begin
Working with electrical components can be dangerous if you’re not careful. Follow these safety precautions to prevent injury:
- Disconnect the Spark Plug Wire: Always disconnect the spark plug wire from the spark plug before working on the ignition system. This prevents accidental starting and electrical shock.
- Allow the Engine to Cool: Let the engine cool down completely before working on it. Hot engine parts can cause burns.
- Work in a Well-Ventilated Area: Gasoline fumes are flammable and can be harmful to your health.
- Wear Safety Glasses and Gloves: Protect your eyes and hands from debris and potential electrical hazards.
- Consult Your Chainsaw’s Repair Manual: Refer to your chainsaw’s repair manual for specific safety instructions and procedures.
Step-by-Step Guide: Checking Your Ignition Coil Pack
Now, let’s get down to business. This step-by-step guide will walk you through the process of checking your chainsaw’s ignition coil pack with a multimeter.
Step 1: Accessing the Ignition Coil Pack
The first step is to locate and access the ignition coil pack. The location of the coil pack varies depending on the chainsaw model, but it’s usually located near the flywheel, under a plastic cover.
- Remove the Engine Cover: Use a screwdriver to remove the screws or clips holding the engine cover in place.
- Locate the Ignition Coil Pack: The ignition coil pack is a small, rectangular component with wires leading to the spark plug and the engine. It’s usually mounted near the flywheel.
Step 2: Visual Inspection
Before you start testing with the multimeter, give the ignition coil pack a thorough visual inspection. Look for any signs of damage, such as:
- Cracks or Breaks: Check for cracks or breaks in the coil pack housing.
- Burn Marks: Look for burn marks or discoloration, which could indicate overheating.
- Corroded Terminals: Inspect the terminals for corrosion or rust.
- Loose Wires: Make sure all wires are securely connected to the coil pack.
If you find any of these issues, the coil pack may need to be replaced, regardless of the multimeter readings.
Step 3: Checking the Primary Resistance
The primary resistance test measures the resistance of the primary winding of the ignition coil pack. This test helps determine if the primary winding is shorted or open.
- Set the Multimeter to Ohms (Ω): Set your multimeter to the lowest ohms range (usually 200 ohms).
- Connect the Multimeter Leads:
- Connect one multimeter lead to the primary terminal of the ignition coil pack (usually the terminal connected to the kill switch wire).
- Connect the other multimeter lead to the ground terminal of the coil pack (usually the metal mounting bracket).
- Read the Resistance: Read the resistance value displayed on the multimeter.
- Compare to Specifications: Compare the reading to the manufacturer’s specifications for your chainsaw model. This information can usually be found in the repair manual.
Interpreting the Results:
- Reading Within Specifications: If the reading is within the specified range, the primary winding is likely good.
- Reading of Zero (0) Ohms: A reading of zero ohms indicates a short circuit in the primary winding. The coil pack needs to be replaced.
- Reading of Infinity (∞) Ohms: A reading of infinity ohms indicates an open circuit in the primary winding. The coil pack needs to be replaced.
For example, a Stihl MS 290’s primary resistance should typically be between 0.5 and 1.5 ohms. If your reading is significantly outside this range, the coil pack is likely faulty.
Step 4: Checking the Secondary Resistance
The secondary resistance test measures the resistance of the secondary winding of the ignition coil pack. This test helps determine if the secondary winding is shorted or open.
- Set the Multimeter to Ohms (Ω): Set your multimeter to a higher ohms range (usually 20k ohms or 20,000 ohms).
- Connect the Multimeter Leads:
- Connect one multimeter lead to the spark plug terminal of the ignition coil pack (the terminal where the spark plug wire connects).
- Connect the other multimeter lead to the ground terminal of the coil pack (usually the metal mounting bracket).
- Read the Resistance: Read the resistance value displayed on the multimeter.
- Compare to Specifications: Compare the reading to the manufacturer’s specifications for your chainsaw model.
Interpreting the Results:
- Reading Within Specifications: If the reading is within the specified range, the secondary winding is likely good.
- Reading of Zero (0) Ohms: A reading of zero ohms indicates a short circuit in the secondary winding. The coil pack needs to be replaced.
- Reading of Infinity (∞) Ohms: A reading of infinity ohms indicates an open circuit in the secondary winding. The coil pack needs to be replaced.
For instance, a Husqvarna 455 Rancher’s secondary resistance should typically be between 3k and 6k ohms (3,000 to 6,000 ohms). Again, refer to your specific model’s repair manual for accurate specifications.
Step 5: Checking the Air Gap
The air gap is the distance between the ignition coil pack and the flywheel. If the air gap is too large or too small, the ignition system may not function properly.
- Locate the Flywheel Magnets: The flywheel has magnets embedded in it that pass by the ignition coil pack as the engine rotates.
- Insert a Feeler Gauge: Insert a feeler gauge of the correct thickness between the ignition coil pack and the flywheel magnet. The correct thickness is usually specified in the chainsaw’s repair manual (typically between 0.010 and 0.020 inches).
- Loosen the Mounting Screws: Loosen the screws holding the ignition coil pack in place.
- Adjust the Air Gap: Slide the ignition coil pack until it makes light contact with the feeler gauge.
- Tighten the Mounting Screws: Tighten the mounting screws while holding the ignition coil pack in place.
- Remove the Feeler Gauge: Remove the feeler gauge. The air gap is now properly adjusted.
I once worked on a vintage McCulloch chainsaw where the air gap was way off. The chainsaw would start, but it ran terribly, lacking power and constantly misfiring. After adjusting the air gap to the correct specification, the chainsaw ran like a champ. It’s a simple adjustment, but it can make a huge difference.
Troubleshooting Common Issues
Even with a multimeter, troubleshooting can sometimes be tricky. Here are some common issues you might encounter and how to address them:
- Inconsistent Readings: Inconsistent readings can be caused by corroded terminals or loose wires. Clean the terminals with a wire brush and make sure all wires are securely connected.
- No Spark Even After Replacing the Coil Pack: If you’ve replaced the coil pack and still have no spark, the problem may lie elsewhere in the ignition system. Check the spark plug, the spark plug wire, and the kill switch.
- Chainsaw Starts but Runs Poorly: If the chainsaw starts but runs poorly, the problem could be a weak spark, a faulty carburetor, or a clogged fuel filter.
The Role of the Kill Switch
Don’t overlook the kill switch! This simple component can cause a world of frustration if it’s malfunctioning. The kill switch grounds the ignition coil, preventing it from producing a spark. If the kill switch is faulty or shorted, it can prevent the chainsaw from starting, even if the coil pack is good.
To test the kill switch:
- Disconnect the Kill Switch Wire: Disconnect the wire leading from the kill switch to the ignition coil pack.
- Try Starting the Chainsaw: If the chainsaw starts with the kill switch wire disconnected, the kill switch is likely the problem.
- Replace the Kill Switch: Replace the kill switch with a new one.
Spark Plug Inspection: A Critical Step
The spark plug is the final link in the ignition chain. A fouled or damaged spark plug can prevent the chainsaw from starting or cause it to run poorly.
- Remove the Spark Plug: Use a spark plug wrench to remove the spark plug from the cylinder head.
- Inspect the Spark Plug: Check the spark plug for the following:
- Cracks or Breaks: Look for cracks or breaks in the ceramic insulator.
- Fouling: Check for excessive carbon buildup or oil deposits on the electrode.
- Electrode Wear: Inspect the electrode for excessive wear or erosion.
- Clean or Replace the Spark Plug: Clean the spark plug with a wire brush or replace it with a new one if necessary.
- Check the Spark Plug Gap: Use a spark plug gap tool to check and adjust the gap between the electrode and the ground electrode. The correct gap is usually specified in the chainsaw’s repair manual.
I’ve seen countless instances where a simple spark plug replacement solved the problem. It’s often the easiest and cheapest fix, so always start there.
Understanding Wood Species and Their Impact on Chainsaw Maintenance
Beyond the ignition system, the type of wood you’re cutting significantly impacts your chainsaw’s lifespan and maintenance needs. Different wood species have varying densities, moisture content, and resin levels, all of which affect the wear and tear on your saw.
Here’s a breakdown of some common wood species and their impact:
- Softwoods (Pine, Fir, Spruce): These woods are generally easier to cut and less abrasive than hardwoods. However, they tend to be resinous, which can lead to buildup on the chain and bar. Regular cleaning is essential.
- Data Point: Softwoods typically have a density of 20-40 lbs per cubic foot.
- Hardwoods (Oak, Maple, Hickory): Hardwoods are denser and more abrasive, requiring sharper chains and more frequent sharpening. They also generate more heat during cutting, so proper chain lubrication is crucial.
- Data Point: Hardwoods typically have a density of 40-60 lbs per cubic foot.
- Exotic Woods (Teak, Mahogany, Ipe): These woods are often extremely dense and oily, requiring specialized cutting techniques and frequent chain sharpening. They can also be corrosive to saw components.
- Data Point: Exotic woods can have a density of 60+ lbs per cubic foot.
I once had a project involving cutting a large quantity of Ipe, a South American hardwood known for its extreme density and durability. I quickly learned that my standard chainsaw chain was no match for this wood. I had to switch to a specialized carbide-tipped chain and sharpen it frequently to maintain optimal cutting performance. The experience taught me the importance of matching the chain and cutting techniques to the specific wood species.
Choosing the Right Chainsaw for the Job
Selecting the right chainsaw for the task at hand is crucial for both efficiency and safety. Consider the following factors when choosing a chainsaw:
- Engine Size: Choose an engine size appropriate for the size of the trees you’ll be felling. Smaller chainsaws (30-40cc) are suitable for limbing and cutting small trees, while larger chainsaws (50cc+) are needed for felling larger trees.
- Bar Length: Select a bar length that’s slightly longer than the diameter of the trees you’ll be cutting. A longer bar allows you to cut through larger trees in a single pass.
- Weight: Consider the weight of the chainsaw, especially if you’ll be using it for extended periods. A lighter chainsaw will reduce fatigue and improve maneuverability.
- Features: Look for features such as anti-vibration systems, chain brakes, and easy-start mechanisms. These features can improve safety and comfort.
Chainsaw Maintenance: A Proactive Approach
Regular chainsaw maintenance is essential for prolonging the life of your saw and ensuring safe operation. Here are some key maintenance tasks:
- Chain Sharpening: Sharpen the chain regularly to maintain optimal cutting performance. A dull chain requires more force to cut, which can increase the risk of kickback.
- Chain Lubrication: Keep the chain properly lubricated to reduce friction and wear. Use a high-quality chain oil and check the oil level frequently.
- Air Filter Cleaning: Clean the air filter regularly to prevent dirt and debris from entering the engine. A clogged air filter can reduce engine power and increase fuel consumption.
- Spark Plug Replacement: Replace the spark plug annually or as needed. A worn spark plug can cause hard starting and poor engine performance.
- Fuel Filter Replacement: Replace the fuel filter annually or as needed. A clogged fuel filter can restrict fuel flow and cause engine stalling.
- Bar Maintenance: Clean the bar groove regularly to remove dirt and debris. Check the bar for wear and damage, and replace it as needed.
Firewood Preparation: From Log to Hearth
For many, the ultimate goal of wood processing is to create firewood for heating their homes. Efficient firewood preparation involves several key steps:
- Felling: Select the appropriate trees for firewood and fell them safely.
- Bucking: Cut the felled trees into manageable lengths (usually 16-24 inches).
- Splitting: Split the logs into smaller pieces to promote faster drying.
- Stacking: Stack the firewood in a well-ventilated area to allow it to dry.
- Seasoning: Allow the firewood to season (dry) for at least six months, or preferably a year, before burning it.
The Importance of Seasoning
Seasoning is critical for producing high-quality firewood. Green (unseasoned) firewood contains a high moisture content, which makes it difficult to ignite and burns inefficiently. Seasoned firewood, on the other hand, burns hotter and cleaner, producing more heat and less smoke.
- Data Point: Green firewood can contain up to 50% moisture content, while seasoned firewood typically has a moisture content of 20% or less.
I’ve experimented with different seasoning methods over the years, from simple stacking in an open area to using covered wood sheds. I’ve found that the key is to ensure good airflow around the wood to promote rapid drying. Stacking the wood off the ground on pallets also helps to prevent moisture from wicking up from the soil.
Case Study: Optimizing Firewood Production in a Small-Scale Operation
Let’s consider a case study of a small-scale firewood production operation. This operation consists of a single individual who harvests and processes firewood on a part-time basis.
- Equipment Used: A Stihl MS 271 chainsaw, a hydraulic log splitter, and a pickup truck.
- Wood Types: Primarily oak and maple.
- Safety Considerations: The operator wears safety glasses, gloves, and hearing protection at all times. He also follows safe felling and splitting practices.
- Challenges: Limited time and resources, fluctuating demand, and competition from larger firewood suppliers.
To optimize production, the operator focuses on the following strategies:
- Efficient Felling Techniques: Using directional felling techniques to minimize waste and improve safety.
- Optimized Bucking Lengths: Cutting the logs into lengths that are easy to handle and split.
- Strategic Stacking: Stacking the firewood in a way that maximizes airflow and minimizes drying time.
- Targeted Marketing: Focusing on local customers and offering competitive pricing.
By implementing these strategies, the operator is able to produce high-quality firewood efficiently and profitably, even with limited resources.
Final Thoughts: Mastering the Art of Wood
From diagnosing ignition coil packs to preparing firewood, the world of wood processing is a fascinating and rewarding pursuit. By understanding the fundamentals of chainsaw maintenance, wood species, and processing techniques, you can not only keep your equipment running smoothly but also produce high-quality firewood that will keep you warm all winter long. So, grab your multimeter, sharpen your chain, and get ready to tackle your next wood processing project with confidence!
