Briggs and Stratton Coil Test Guide (Spark Fix for Woodcutters)
Alright, let’s get right down to brass tacks. You’re a woodcutter, and your chainsaw’s giving you grief. The most frustrating problem? No spark. You’ve checked the fuel, the air filter, even the pull cord. Now, the finger points to the ignition coil – that little devil responsible for sending the electrical jolt to the spark plug.
This guide is your fast track to diagnosing and fixing a faulty Briggs & Stratton ignition coil. We’re not going to beat around the bush with unnecessary theory. We’re diving straight into practical tests, proven techniques, and the kind of hands-on knowledge I’ve accumulated over years of felling trees and splitting firewood.
Briggs & Stratton Coil Test Guide (Spark Fix for Woodcutters)
The Agony of a Dead Saw: My Own Sparkless Nightmare
Let me tell you a story. I was once deep in the backwoods of Oregon, harvesting some beautiful Douglas fir for a custom timber frame project. I had a deadline looming, and the weather was threatening to turn. My trusty old saw, a workhorse I’d relied on for years, suddenly sputtered and died. No spark. Just dead silence.
Panic set in. I was miles from civilization, with a mountain of logs to cut. After a few choice words and a frantic check of the basics, I realized the problem was likely the ignition coil. I didn’t have a spare, and turning back wasn’t an option.
That day, I learned a valuable lesson. Diagnosing and fixing an ignition coil in the field is a skill every woodcutter needs. It saved my bacon that day, and it can save yours too.
Understanding the Ignition Coil: The Heart of the Spark
Before we get our hands dirty, let’s quickly understand what an ignition coil does. Think of it as a tiny transformer. It takes the low-voltage electricity from the engine’s magneto (or battery system in some cases) and boosts it to the thousands of volts needed to create a spark at the spark plug. That spark ignites the fuel-air mixture, powering your saw.
When an ignition coil fails, it can be due to several reasons:
- Broken windings: The coil has internal windings that can break down over time due to heat, vibration, or corrosion.
- Short circuits: Moisture or damage can cause a short circuit within the coil, preventing it from producing the necessary voltage.
- Physical damage: Cracks, breaks, or corrosion can physically damage the coil, rendering it useless.
- Air Gap Issues: The air gap between the coil and the flywheel is critical. Too big or too small, and you won’t get a spark.
Essential Tools for Coil Testing
Before you start poking around, gather these essential tools:
- Spark plug wrench: To remove the spark plug.
- Spark plug tester: A simple tool to visually confirm if a spark is present.
- Multimeter: A digital multimeter is crucial for measuring resistance and voltage. Get one with good reviews and a reputation for accuracy.
- Feeler gauge: For setting the air gap between the coil and the flywheel.
- Screwdrivers: A variety of sizes, both flathead and Phillips.
- Socket set: For removing the coil cover and any other necessary parts.
- Wire brush: To clean any corrosion from the coil and surrounding areas.
- Safety glasses: Always protect your eyes!
- Work gloves: To protect your hands.
- Briggs & Stratton service manual (optional but highly recommended): This will provide specific instructions and diagrams for your particular engine model.
Safety First: Disconnect and Ground
Before you even think about touching anything electrical, follow these safety precautions:
- Disconnect the spark plug wire: This is crucial to prevent accidental shocks. Pull the wire directly from the spark plug boot, not the wire itself.
- Ground the spark plug wire: Attach the spark plug wire to the engine block or another metal part of the saw. This will discharge any residual electricity.
- Remove the spark plug: This will make it easier to turn the engine over during testing.
Testing for Spark: The Quick and Dirty Method
The first and simplest test is the visual spark test.
- Reattach the spark plug to the spark plug wire.
- Hold the spark plug against the engine block, ensuring good metal-to-metal contact. The threads of the spark plug should be touching clean metal.
- Pull the starter cord. Watch the gap between the spark plug electrodes.
- Observe. You should see a strong, blue spark jumping across the gap. A weak, yellow spark, or no spark at all, indicates a problem.
If you see a good, strong spark, your ignition coil is likely working fine. The problem may lie elsewhere, such as a fouled spark plug, a fuel issue, or a compression problem.
If you don’t see a spark, or the spark is weak, proceed to the next tests.
Testing the Ignition Coil with a Multimeter: The Resistance Test
The resistance test is a more precise way to check the condition of the ignition coil’s windings. You’ll need your multimeter for this.
- Set your multimeter to the ohms (Ω) setting. You’ll likely need to select a range. Start with the lowest range and increase it until you get a reading.
- Locate the primary and secondary terminals on the ignition coil. The primary terminal is usually a small blade or connector where the kill wire attaches. The secondary terminal is the spark plug wire itself.
- Measure the primary resistance. Place one multimeter probe on the primary terminal and the other probe on the engine block (ground). Record the reading.
- Measure the secondary resistance. Place one multimeter probe on the spark plug wire (you may need to use a small probe to insert into the boot) and the other probe on the engine block (ground). Record the reading.
- Compare your readings to the manufacturer’s specifications. This is where that Briggs & Stratton service manual comes in handy. The manual will provide the expected resistance range for your specific engine model.
Interpreting the Results:
- If the resistance readings are within the specified range, the coil is likely good. However, it’s not a foolproof test. The coil could still be failing under load.
- If the resistance reading is significantly higher than specified, the coil has an open circuit in the windings. This means the coil is definitely bad and needs to be replaced.
- If the resistance reading is significantly lower than specified, the coil has a short circuit in the windings. This also means the coil is bad and needs to be replaced.
- If you get an “OL” or “infinite resistance” reading, the circuit is open. This indicates a broken wire or connection within the coil.
Example:
Let’s say your Briggs & Stratton engine manual specifies a primary resistance of 3-5 ohms and a secondary resistance of 5,000-8,000 ohms.
- If you measure a primary resistance of 4 ohms and a secondary resistance of 6,500 ohms, the coil is likely good.
- If you measure a primary resistance of 10 ohms and a secondary resistance of 12,000 ohms, the coil is likely bad.
- If you measure a primary resistance of 0 ohms and a secondary resistance of 1,000 ohms, the coil is likely bad.
The Air Gap Test: Crucial for Spark Generation
The air gap is the distance between the ignition coil and the flywheel. This gap is critical for generating the magnetic field needed to induce voltage in the coil. If the air gap is too wide or too narrow, the coil won’t produce a spark.
- Locate the ignition coil and the flywheel. The flywheel is the rotating metal disc with magnets embedded in it.
- Loosen the mounting bolts on the ignition coil. Just enough so you can move the coil slightly.
- Insert a feeler gauge of the specified thickness between the coil and the flywheel. The specified air gap is usually around 0.010-0.015 inches (0.25-0.38 mm). Check your engine’s service manual for the exact specification.
- Push the coil against the feeler gauge and tighten the mounting bolts. This will ensure the correct air gap.
- Remove the feeler gauge.
- Test for spark again.
Why is the air gap so important?
The magnets in the flywheel pass by the ignition coil as the engine rotates. This creates a changing magnetic field, which induces a voltage in the coil’s windings. The size of the air gap affects the strength of the magnetic field.
- If the air gap is too wide, the magnetic field will be weak, and the coil won’t produce enough voltage to create a spark.
- If the air gap is too narrow, the coil may rub against the flywheel, causing damage and potentially shorting out the coil.
Checking the Kill Wire: A Simple but Often Overlooked Culprit
The kill wire is a small wire that connects to the ignition coil and runs to the engine’s switch or shut-off mechanism. When the switch is in the “off” position, the kill wire grounds the ignition coil, preventing it from producing a spark.
If the kill wire is damaged, shorted, or improperly connected, it can prevent the engine from starting.
- Inspect the kill wire for any signs of damage. Look for frayed wires, broken insulation, or loose connections.
- Disconnect the kill wire from the ignition coil.
- Test for spark again.
If the engine starts with the kill wire disconnected, the problem is likely in the kill switch or the wiring between the switch and the coil. You’ll need to troubleshoot the kill switch and wiring to find the short circuit or open connection.
If the engine still doesn’t start with the kill wire disconnected, the problem is likely in the ignition coil itself.
The “Cardboard Trick”: A Field Expedient Air Gap Tool
I learned this trick from an old-timer logger in the Pacific Northwest. If you’re in the field and don’t have a feeler gauge handy, you can use a piece of cardboard to set the air gap.
- Find a piece of cardboard that is approximately the same thickness as the specified air gap. A business card or a piece of cereal box cardboard often works well.
- Loosen the mounting bolts on the ignition coil.
- Insert the cardboard between the coil and the flywheel.
- Push the coil against the cardboard and tighten the mounting bolts.
- Remove the cardboard.
- Test for spark again.
This is a quick and dirty method, but it can get you out of a pinch. Just remember to replace the cardboard with a proper feeler gauge when you get back to your shop.
When to Replace the Ignition Coil: The Point of No Return
After performing all the tests, if you’re still not getting a spark, it’s likely time to replace the ignition coil. There’s no magic bullet for a completely dead coil. Trying to repair it is usually a waste of time and effort.
Signs that indicate a coil needs replacement:
- No spark after performing all the tests.
- Cracked or broken coil housing.
- Visible corrosion on the coil windings.
- Burned or melted coil insulation.
- Resistance readings outside the specified range.
Choosing a Replacement Coil:
- Buy a genuine Briggs & Stratton replacement coil. These are designed specifically for your engine and will provide the best performance and reliability.
- If you’re on a budget, you can consider an aftermarket coil. However, be sure to choose a reputable brand and read reviews before buying.
- Make sure the replacement coil is compatible with your engine model. Check the part number in your engine’s service manual.
Installing the New Ignition Coil: A Step-by-Step Guide
Installing a new ignition coil is a relatively straightforward process.
- Disconnect the spark plug wire and ground it.
- Remove the coil cover and any other parts that are blocking access to the ignition coil.
- Disconnect the kill wire from the old ignition coil.
- Remove the mounting bolts that hold the old ignition coil in place.
- Remove the old ignition coil.
- Install the new ignition coil.
- Set the air gap using a feeler gauge.
- Connect the kill wire to the new ignition coil.
- Reinstall the coil cover and any other parts that you removed.
- Connect the spark plug wire.
- Test for spark.
Troubleshooting Common Issues After Coil Replacement
Even after replacing the ignition coil, you might still encounter problems. Here are some common issues and how to troubleshoot them:
- No spark after replacement: Double-check the air gap, kill wire connection, and spark plug. Make sure you bought the correct replacement coil.
- Weak spark: Check the flywheel magnets for damage or debris. Clean the magnets with a wire brush.
- Engine starts but runs poorly: Check the spark plug gap and condition. Make sure the fuel is fresh and the air filter is clean.
- Engine starts but dies quickly: Check the fuel system for clogs or leaks. The carburetor may need cleaning or adjustment.
Preventative Maintenance: Keeping Your Coil Healthy
The best way to avoid ignition coil problems is to perform regular preventative maintenance.
- Keep the engine clean and dry. Moisture and dirt can damage the coil.
- Inspect the coil regularly for cracks, breaks, or corrosion.
- Check the air gap periodically and adjust as needed.
- Replace the spark plug regularly. A worn spark plug can put extra strain on the ignition coil.
- Use fresh, high-quality fuel. Old or contaminated fuel can cause engine problems that can damage the coil.
- Store the chainsaw in a dry place when not in use.
Wood Types and Their Impact on Chainsaw Performance
The type of wood you’re cutting can also affect your chainsaw’s performance and potentially impact the ignition system. Hardwoods like oak and maple require more power to cut than softwoods like pine and fir. This increased load can put extra stress on the engine and ignition coil, potentially leading to premature failure.
Here’s a breakdown of common wood types and their impact:
- Softwoods (Pine, Fir, Cedar): Easier to cut, less stress on the saw, but tend to dull chains faster due to resin content.
- Data Point: Softwoods generally require 20-30% less power to cut compared to hardwoods.
- Hardwoods (Oak, Maple, Hickory): More difficult to cut, higher stress on the saw, but provide more heat when burned as firewood.
- Data Point: Hardwoods have a density that is 50-100% greater than softwoods, requiring more force to cut.
- Exotic Hardwoods (Ipe, Teak): Extremely dense and hard, requiring specialized cutting techniques and heavy-duty equipment. Can generate significant heat during cutting.
- Case Study: A furniture maker I know tried cutting Ipe with a standard chainsaw and burned out his coil within a week. These woods require carbide-tipped chains and more powerful saws.
Choosing the Right Wood for Firewood:
- BTU Content: Hardwoods generally have a higher BTU (British Thermal Unit) content than softwoods, meaning they produce more heat when burned.
- Example: Oak has approximately 28 million BTUs per cord, while pine has around 20 million BTUs per cord.
- Burning Time: Hardwoods burn longer and more consistently than softwoods.
- Smoke Production: Softwoods tend to produce more smoke due to their higher resin content.
- Ease of Splitting: Some hardwoods, like oak, can be difficult to split, while softwoods are generally easier.
The Business Side: Chainsaw Maintenance and Profitability
For professional woodcutters and firewood producers, chainsaw maintenance is directly linked to profitability. Downtime due to equipment failure translates to lost revenue.
- Data Point: A study by the Forest Resources Association found that unplanned downtime costs logging operations an average of $500-$1000 per day.
- Insight: Implementing a proactive maintenance program, including regular ignition coil checks, can significantly reduce downtime and increase profitability.
Strategies for Maximizing Uptime:
- Regular Inspections: Conduct daily inspections of your chainsaw, including the ignition coil, spark plug, air filter, and fuel system.
- Preventative Maintenance Schedule: Develop a preventative maintenance schedule based on your saw’s usage and the manufacturer’s recommendations.
- Spare Parts Inventory: Keep a stock of essential spare parts, such as ignition coils, spark plugs, and air filters.
- Training: Train your employees on proper chainsaw maintenance and troubleshooting techniques.
- Record Keeping: Maintain detailed records of all maintenance and repairs.
The Future of Chainsaw Technology: Ignition Systems and Beyond
Chainsaw technology is constantly evolving, and ignition systems are no exception. Manufacturers are developing more advanced ignition systems that are more reliable, efficient, and durable.
- Electronic Ignition Systems: These systems use electronic components to control the timing and duration of the spark, resulting in improved performance and fuel efficiency.
- Digital Ignition Systems: These systems use microprocessors to optimize the ignition timing based on engine speed and load.
- Battery-Powered Chainsaws: These saws use electric motors and lithium-ion batteries, eliminating the need for a traditional ignition system.
The Rise of Battery-Powered Saws:
Battery-powered chainsaws are becoming increasingly popular, especially for homeowners and light-duty applications.
- Advantages: Quieter operation, lower maintenance, no emissions, and easier starting.
- Disadvantages: Limited runtime, lower power compared to gas-powered saws, and higher initial cost.
- Trend: Battery technology is rapidly improving, and battery-powered chainsaws are becoming more powerful and longer-lasting.
Conclusion: Sparking Success in Woodcutting
Troubleshooting a Briggs & Stratton ignition coil might seem daunting at first, but with the right tools, knowledge, and a bit of patience, you can diagnose and fix the problem yourself. Remember to prioritize safety, follow the steps outlined in this guide, and don’t be afraid to consult your engine’s service manual.
Whether you’re a seasoned logger or a weekend warrior splitting firewood, a reliable chainsaw is essential. By understanding the basics of ignition coil function and maintenance, you can keep your saw running smoothly and efficiently, ensuring you’re always ready to tackle your next woodcutting project.
And remember my story in the Oregon backwoods. A little knowledge can go a long way when you’re miles from civilization and relying on your own skills to get the job done. Now get out there and make some sawdust!
