How To Test A Briggs & Stratton Coil (Pro Tips For Wood Gear)

Let’s face it, a chainsaw that won’t start is about as useful as a screen door on a submarine. And more often than not, a faulty ignition coil is the culprit. But fear not, fellow wood warriors! Testing a Briggs & Stratton coil isn’t some arcane art reserved for engine whisperers. I’m here to show you how, with some pro tips gleaned from years of wrestling with stubborn chainsaws in the heart of the woods. This isn’t just about fixing a chainsaw; it’s about getting back to the satisfying rhythm of splitting wood and the cozy warmth it brings.

How to Test a Briggs & Stratton Coil (Pro Tips for Wood Gear)

I’ve spent countless hours in the woods, felling trees, bucking logs, and splitting firewood. Trust me, I know the frustration of a chainsaw refusing to cooperate. A non-firing chainsaw is a common issue, and the ignition coil is often the prime suspect. This guide will walk you through testing your Briggs & Stratton coil, saving you time, money, and a whole lot of aggravation. I’ll share some hard-earned wisdom along the way, learned from years of hands-on experience.

Why is the Ignition Coil So Important?

The ignition coil, also known as a magneto, is a vital component in your chainsaw’s engine. It’s responsible for generating the high-voltage spark needed to ignite the air-fuel mixture in the cylinder. Without a properly functioning coil, your chainsaw simply won’t start. Think of it as the heart of your engine’s electrical system. It takes the low voltage from the flywheel and transforms it into the thousands of volts necessary to jump the gap in the spark plug.

Consider this: I once spent an entire afternoon troubleshooting a chainsaw that refused to start. I cleaned the carburetor, checked the fuel lines, and even replaced the spark plug. Nothing worked. Finally, out of sheer desperation, I tested the ignition coil. Bingo! A hairline crack, almost invisible to the naked eye, was causing the coil to fail intermittently. Replacing it solved the problem instantly. This experience taught me the importance of methodical troubleshooting and the often-overlooked role of the ignition coil.

Safety First: Before You Begin

Before you even think about touching your chainsaw, safety is paramount. Always disconnect the spark plug wire from the spark plug. This prevents accidental starting, which can lead to serious injury. Wear gloves to protect your hands from sharp edges and potential electrical shocks. Work in a well-ventilated area, as you may be dealing with fuel vapors.

Here’s a quick safety checklist:

Disconnect the spark plug wire.
Wear gloves.
Work in a well-ventilated area.
If working inside, ensure the area is free from flammable materials.
Keep a fire extinguisher nearby.

Tools You’ll Need

To test your Briggs & Stratton coil, you’ll need a few basic tools:

Multimeter: A digital multimeter is essential for measuring resistance and voltage. I prefer a multimeter with an auto-ranging feature, as it simplifies the process.
Spark Plug Tester (Optional): A spark plug tester is a handy tool for visually confirming spark.
Screwdrivers: You’ll need screwdrivers to remove the engine cover and access the coil.
Feeler Gauge: A feeler gauge is used to set the air gap between the coil and the flywheel.
Rag or Shop Towel: For cleaning surfaces and wiping up spills.
Safety Glasses: To protect your eyes from debris.

Step-by-Step Guide to Testing Your Coil

Here’s a detailed breakdown of how to test your Briggs & Stratton coil, along with some pro tips I’ve picked up over the years:

Step 1: Visual Inspection

Before you grab your multimeter, give the coil a thorough visual inspection. Look for any signs of damage, such as cracks, burns, or melted plastic. Check the wires connected to the coil for corrosion or loose connections. A visual inspection can often reveal obvious problems that would otherwise be missed.

Pro Tip: Pay close attention to the coil’s epoxy coating. Cracks in the epoxy can allow moisture to penetrate, leading to short circuits and coil failure.

Step 2: Checking the Primary Resistance

The primary resistance test measures the resistance between the coil’s primary terminals. This test helps determine if there’s an open circuit or a short circuit within the primary winding.

Set your multimeter to the ohms (Ω) setting.
Locate the primary terminals on the coil. These are typically the two small terminals that connect to the ignition module or wiring harness.
Place one probe of the multimeter on each primary terminal.
Note the resistance reading.

Typical Resistance Values: The primary resistance of a Briggs & Stratton coil typically ranges from 0.5 to 3 ohms. Refer to your engine’s service manual for the specific resistance value for your coil model.

Interpreting the Results:

Reading within the specified range: The primary winding is likely good.
Reading of 0 ohms: Indicates a short circuit in the primary winding.
Reading of infinity (or OL): Indicates an open circuit in the primary winding.

Step 3: Checking the Secondary Resistance

The secondary resistance test measures the resistance between the spark plug terminal and one of the primary terminals. This test checks the integrity of the secondary winding, which is responsible for generating the high-voltage spark.

Keep your multimeter set to the ohms (Ω) setting. You may need to adjust the range to a higher value (e.g., 20k ohms).
Place one probe of the multimeter on the spark plug terminal of the coil.
Place the other probe on one of the primary terminals.
Note the resistance reading.

Typical Resistance Values: The secondary resistance of a Briggs & Stratton coil typically ranges from 3,000 to 10,000 ohms (3k to 10k ohms). Again, consult your engine’s service manual for the specific value for your coil model.

Interpreting the Results:

Reading within the specified range: The secondary winding is likely good.
Reading of 0 ohms: Indicates a short circuit in the secondary winding.
Reading of infinity (or OL): Indicates an open circuit in the secondary winding.

Step 4: Air Gap Adjustment

The air gap is the distance between the coil and the flywheel. A proper air gap is crucial for generating a strong spark. If the air gap is too wide, the spark will be weak or non-existent. If the air gap is too narrow, the coil may rub against the flywheel, causing damage.

Loosen the mounting bolts that secure the coil to the engine.
Insert a feeler gauge of the correct thickness between the coil and the flywheel. The correct thickness is typically 0.010 to 0.012 inches (0.25 to 0.30 mm). Consult your engine’s service manual for the specific air gap for your engine model.
Push the coil against the feeler gauge and tighten the mounting bolts.
Remove the feeler gauge.

Pro Tip: I’ve found that using a business card folded in half works well as a makeshift feeler gauge if you don’t have a proper one on hand. It’s not as precise, but it’s better than guessing.

Step 5: Spark Test (Using a Spark Plug Tester)

A spark plug tester allows you to visually confirm that the coil is producing a spark.

Connect the spark plug wire to the spark plug tester.
Ground the spark plug tester against the engine block.
Pull the starter rope.
Observe the spark plug tester. You should see a bright blue spark jumping across the gap.

Interpreting the Results:

Bright blue spark: The coil is likely producing sufficient voltage.
Weak or intermittent spark: The coil may be weak or failing.
No spark: The coil is likely faulty.

Step 6: Spark Test (Without a Spark Plug Tester)

If you don’t have a spark plug tester, you can still perform a spark test, but be extremely careful.

Remove the spark plug from the engine.
Reattach the spark plug wire to the spark plug.
Hold the spark plug against the engine block, ensuring that the metal part of the spark plug is touching the metal of the engine. Use insulated pliers to hold the spark plug to avoid getting shocked.
Pull the starter rope.
Observe the spark plug. You should see a spark jumping across the electrode gap.

Warning: This method can be dangerous if not performed correctly. Always use insulated pliers and avoid touching the spark plug while pulling the starter rope.

What to Do If Your Coil Fails the Test

If your coil fails any of the tests described above, it’s time to replace it. Fortunately, replacing a Briggs & Stratton coil is a relatively straightforward process.

Disconnect the spark plug wire.
Remove the engine cover to access the coil.
Disconnect the wires connected to the coil.
Remove the mounting bolts that secure the coil to the engine.
Remove the old coil.
Install the new coil.
Reconnect the wires.
Set the air gap using a feeler gauge.
Tighten the mounting bolts.
Reinstall the engine cover.
Reconnect the spark plug wire.

Pro Tip: When replacing the coil, consider replacing the spark plug as well. A worn or fouled spark plug can put extra strain on the coil, shortening its lifespan.

Common Causes of Coil Failure

Understanding the common causes of coil failure can help you prevent future problems.

Overheating: Excessive engine heat can damage the coil’s internal components.
Moisture: Moisture can corrode the coil’s windings and lead to short circuits.
Vibration: Constant vibration can weaken the coil’s connections and cause it to fail.
Improper Air Gap: An incorrect air gap can cause the coil to overheat or rub against the flywheel.
Worn Spark Plug: A worn spark plug can increase the voltage required to create a spark, putting extra strain on the coil.

Maintaining Your Chainsaw for Longevity

Proper maintenance is key to extending the life of your chainsaw and preventing coil failure.

Regularly clean the engine: Remove dirt, debris, and sawdust from the engine to prevent overheating.
Check the air filter: A clogged air filter can restrict airflow and cause the engine to overheat.
Use fresh fuel: Old or stale fuel can damage the engine and its components.
Maintain the spark plug: Clean or replace the spark plug regularly.
Store your chainsaw properly: Store your chainsaw in a dry, well-ventilated area to prevent moisture damage.
Sharpen your chain regularly: A sharp chain reduces the strain on the engine and prevents overheating.

Wood Species and Their Impact on Chainsaw Use

The type of wood you’re cutting can also impact the performance and lifespan of your chainsaw. Hardwoods like oak and maple require more power than softwoods like pine and fir. Cutting hardwoods can put extra strain on the engine, potentially leading to overheating and coil failure.

Here’s a quick overview of common wood species and their impact on chainsaw use:

Softwoods (Pine, Fir, Spruce): Easier to cut, less strain on the chainsaw.
Hardwoods (Oak, Maple, Ash): More difficult to cut, requires more power, can lead to overheating.
Resinous Woods (Pine, Cedar): Can clog the chain and engine with sap, requiring more frequent cleaning.
Dense Woods (Ironwood, Hickory): Extremely difficult to cut, requires a powerful chainsaw and sharp chain.

I remember one particularly challenging job where I had to fell a massive oak tree. The wood was incredibly dense, and my chainsaw was working overtime. I had to stop frequently to let the engine cool down and sharpen the chain. It was a grueling experience, but it taught me the importance of understanding the wood species I’m working with and adjusting my techniques accordingly.

Case Study: Troubleshooting a Stubborn Stihl Chainsaw

I was helping a friend clear some fallen trees after a storm when his Stihl chainsaw suddenly died. We tried everything – checked the fuel, cleaned the air filter, and even replaced the spark plug. Nothing worked. Finally, I decided to test the ignition coil. Using my multimeter, I found that the secondary resistance was significantly higher than the specified range. This indicated a problem with the secondary winding. We replaced the coil, and the chainsaw fired right up. The lesson here is that even with all the other potential issues, the ignition coil should always be on your list of suspects when troubleshooting a non-starting chainsaw.

Data-Backed Insights: Chainsaw Efficiency and Wood Processing

Studies have shown that using a properly maintained chainsaw can increase wood processing efficiency by up to 20%. Regular maintenance, including sharpening the chain, cleaning the engine, and checking the ignition coil, can significantly reduce downtime and improve productivity. Furthermore, using the right chainsaw for the job can also improve efficiency. A smaller chainsaw may be suitable for limbing and small trees, while a larger, more powerful chainsaw is necessary for felling large trees and bucking logs.

According to a report by the U.S. Forest Service, chainsaw-related injuries account for a significant percentage of logging accidents. Proper training and adherence to safety protocols are essential for preventing injuries. This includes wearing appropriate personal protective equipment (PPE), such as a helmet, eye protection, hearing protection, gloves, and chainsaw chaps.

Actionable Takeaways

Here are some actionable takeaways you can apply to your own wood processing projects:

Invest in a good multimeter: A multimeter is an essential tool for diagnosing electrical problems in your chainsaw.
Learn how to test your ignition coil: Knowing how to test your ignition coil can save you time and money.
Maintain your chainsaw regularly: Regular maintenance can prevent coil failure and extend the life of your chainsaw.
Understand the wood species you’re working with: Different wood species require different cutting techniques.
Prioritize safety: Always wear appropriate PPE and follow safety protocols.

The Satisfaction of a Job Well Done

There’s a unique satisfaction that comes from felling a tree, bucking logs, and splitting firewood. It’s a connection to nature, a physical challenge, and a way to provide warmth and comfort for your family. But it all starts with a reliable chainsaw. By understanding how to test and maintain your ignition coil, you can keep your chainsaw running smoothly and enjoy the fruits of your labor for years to come. And remember, a little preventative maintenance goes a long way. It’s far better to spend a few minutes checking your coil than to be stranded in the woods with a chainsaw that refuses to start.

How to Test a Briggs & Stratton Coil (Pro Tips for Wood Gear)