Stihl TS420 Ignition Coil Repair Tips (5 Pro Hacks)
As someone who’s spent countless hours in the field, wrestling with logs, tuning up saws, and splitting wood, I know firsthand the importance of reliable equipment. The Stihl TS420 cut-off saw is a workhorse, a real lifesaver when you’re dealing with concrete, asphalt, or even tough timber. But like any piece of machinery, it can have its hiccups. And one of the most common culprits? The ignition coil. A faulty ignition coil can bring your entire operation to a grinding halt, costing you valuable time and money.
This article is born from my own experiences, both good and bad, with the Stihl TS420. I’ve learned these “5 Pro Hacks” through trial and error, through countless hours of troubleshooting in the field, and through the invaluable advice of seasoned mechanics. These aren’t just theoretical tips; they’re practical, battle-tested methods that will help you diagnose, repair, and even prevent ignition coil problems on your TS420.
I’m going to walk you through everything you need to know, from understanding the basics of the ignition system to performing advanced troubleshooting steps. We’ll cover the tools you’ll need, the safety precautions you must take, and the step-by-step procedures for testing and replacing your ignition coil. And most importantly, I’ll share my own personal insights and experiences along the way, so you can avoid the common pitfalls and get your TS420 back up and running quickly and efficiently. So, let’s dive in and get our hands dirty!
Stihl TS420 Ignition Coil Repair Tips (5 Pro Hacks)
Understanding the Ignition System: A Logger’s Perspective
Before we start wrenching, let’s understand the basics. The ignition system is the heart of your Stihl TS420. It’s what creates the spark that ignites the fuel-air mixture, powering the engine. The ignition coil is a key component, transforming the low-voltage current from the flywheel magneto into the high-voltage spark needed to jump the gap at the spark plug.
Think of it like this: the flywheel is the muscle, the ignition coil is the transformer, and the spark plug is the deliverer of the power. If any of these elements fail, the entire system breaks down.
A faulty ignition coil can manifest in several ways:
- No spark: The most obvious symptom. The engine simply won’t start.
- Weak spark: The engine starts, but runs poorly, sputters, or lacks power.
- Intermittent spark: The engine runs fine for a while, then suddenly dies or runs erratically.
From my experience, intermittent issues are the most frustrating. You spend hours troubleshooting, only for the saw to work perfectly… for a little while. Then the problem returns. This is why a systematic approach is crucial.
Data Point: According to a study by the Equipment Dealers Association (EDA), ignition system failures account for approximately 15% of all small engine repairs. This highlights the importance of understanding and maintaining this critical component.
Pro Hack #1: The Visual Inspection: Your First Line of Defense
Before you even think about grabbing a wrench, start with a thorough visual inspection. This is the “look before you leap” approach.
- Check the Wiring: Look for frayed, cracked, or disconnected wires leading to and from the ignition coil. Pay close attention to the connections. Corrosion and loose connections are common culprits. I’ve seen instances where a simple wire reattachment solved the entire problem.
- Inspect the Coil Body: Examine the coil itself for cracks, burns, or any signs of physical damage. If the coil body is cracked, moisture can seep in, causing short circuits and ultimately leading to failure.
- Check the Spark Plug Wire and Boot: The spark plug wire carries the high-voltage current to the spark plug. Ensure it’s securely connected to both the coil and the spark plug. The spark plug boot (the rubber cap that covers the spark plug) should be intact and free of cracks.
Personal Story: I once spent an entire afternoon tearing apart a TS420, convinced the ignition coil was shot. Turns out, a tiny crack in the spark plug boot was allowing the spark to ground out. A $5 boot replacement and I was back in business.
Actionable Tip: Use a magnifying glass to inspect the wiring and coil body for hairline cracks or subtle damage that might be missed with the naked eye.
Pro Hack #2: The Spark Test: Proving the Coil’s Worth
If the visual inspection doesn’t reveal any obvious problems, the next step is to perform a spark test. This will tell you whether the ignition coil is actually producing a spark.
Tools Needed:
- Spark plug wrench
- Insulated pliers
- A clean, dry surface
Procedure:
- Remove the spark plug from the engine.
- Reattach the spark plug wire to the spark plug.
- Hold the threaded metal part of the spark plug against a clean, unpainted metal part of the engine (this provides a ground). Use insulated pliers to avoid getting shocked.
- Pull the starter cord. Observe the spark plug gap. You should see a strong, blue spark jumping across the gap.
Interpreting the Results:
- Strong, blue spark: The ignition coil is likely working correctly. The problem may lie elsewhere (fuel system, compression, etc.).
- Weak, yellow spark: The ignition coil may be weak and needs replacement.
- No spark: The ignition coil is likely faulty.
Caution: Always use insulated pliers when performing a spark test to avoid electric shock.
Data Point: A healthy spark should be approximately 6-8mm long and blue in color. A weak or yellow spark indicates a problem with the ignition system.
Pro Hack #3: The Air Gap Adjustment: Fine-Tuning Performance
The air gap is the distance between the ignition coil and the flywheel. This gap is critical for proper ignition timing and spark generation. If the air gap is too wide or too narrow, the ignition coil won’t function correctly.
Tools Needed:
- Feeler gauge (typically 0.010″ – 0.014″ or as specified in your TS420’s manual)
- Screwdriver
Procedure:
- Locate the ignition coil on the engine. It’s typically mounted near the flywheel.
- Loosen the mounting screws that hold the ignition coil in place. Don’t remove them completely.
- Insert the feeler gauge between the ignition coil and the flywheel magnet.
- Gently push the ignition coil towards the flywheel until it contacts the feeler gauge.
- Tighten the mounting screws to secure the ignition coil in place.
- Remove the feeler gauge.
Why This Matters: I’ve seen cases where a slightly misadjusted air gap caused intermittent starting problems and reduced engine power. A small adjustment can make a big difference.
Actionable Tip: Always consult your Stihl TS420’s manual for the correct air gap specification. Using the wrong air gap can damage the ignition coil or the flywheel.
Pro Hack #4: The Resistance Test: Digging Deeper with a Multimeter
If the spark test is inconclusive or you suspect a more complex issue, a resistance test can help you diagnose the ignition coil with greater precision. This test measures the electrical resistance within the coil, which can indicate internal damage or short circuits.
Tools Needed:
- Multimeter (capable of measuring resistance)
Procedure:
- Disconnect the spark plug wire from the spark plug.
- Set the multimeter to the resistance (Ohms) setting.
- Connect one multimeter probe to the spark plug wire terminal on the ignition coil.
- Connect the other multimeter probe to the engine ground (a clean, unpainted metal part of the engine).
- Record the resistance reading.
- Consult your Stihl TS420’s service manual for the correct resistance specifications for the ignition coil.
Interpreting the Results:
- Resistance within the specified range: The ignition coil is likely functioning correctly.
- Resistance outside the specified range (too high or too low): The ignition coil is likely faulty and needs replacement.
- Zero resistance (short circuit): The ignition coil is definitely faulty and needs replacement.
- Infinite resistance (open circuit): The ignition coil is definitely faulty and needs replacement.
Personal Insight: I once diagnosed an ignition coil problem on a TS420 that was causing the engine to overheat. The resistance test revealed a short circuit within the coil, which was causing the engine to run lean and overheat. Replacing the coil solved the problem.
Data Point: According to Stihl’s service manuals, the primary resistance of a TS420 ignition coil should typically be between 0.5 and 2.0 Ohms, while the secondary resistance (measured from the spark plug wire terminal to ground) should be between 4,000 and 8,000 Ohms. Always refer to your specific manual for accurate values.
Pro Hack #5: The Replacement Process: Swapping in a New Coil
If all the tests point to a faulty ignition coil, the only solution is to replace it. This is a relatively straightforward process, but it’s important to follow the correct steps to avoid damaging the new coil or the engine.
Tools Needed:
- Screwdriver
- Wrench
- New ignition coil (ensure it’s the correct part for your Stihl TS420)
Procedure:
- Disconnect the spark plug wire from the spark plug.
- Remove the engine cover to access the ignition coil.
- Disconnect the wiring from the old ignition coil.
- Remove the mounting screws that hold the old ignition coil in place.
- Remove the old ignition coil.
- Install the new ignition coil, ensuring it’s properly aligned with the flywheel.
- Tighten the mounting screws to secure the new ignition coil in place.
- Reconnect the wiring to the new ignition coil.
- Adjust the air gap (as described in Pro Hack #3).
- Reinstall the engine cover.
- Reconnect the spark plug wire to the spark plug.
- Start the engine and test for proper operation.
Common Mistakes to Avoid:
- Using the wrong ignition coil: Always ensure you’re using the correct part for your specific Stihl TS420 model.
- Over-tightening the mounting screws: This can damage the ignition coil or the engine.
- Forgetting to adjust the air gap: This is crucial for proper ignition timing.
- Damaging the wiring: Be careful when disconnecting and reconnecting the wiring to avoid damaging the wires or the connectors.
Personal Tip: When installing a new ignition coil, I always apply a small amount of dielectric grease to the wiring connections. This helps prevent corrosion and ensures a good electrical connection.
Sourcing Strategies: I usually buy my replacement parts from reputable online retailers or my local Stihl dealer. While cheaper aftermarket parts are available, I’ve found that OEM (Original Equipment Manufacturer) parts tend to be more reliable and last longer in the long run.
Preventative Maintenance: Keeping Your TS420 Running Strong
Prevention is always better than cure. Here are a few tips to help you prevent ignition coil problems on your Stihl TS420:
- Keep the engine clean: Dirt and debris can accumulate around the ignition coil, causing overheating and premature failure. Regularly clean the engine with compressed air or a brush.
- Use fresh fuel: Old or stale fuel can damage the ignition system. Always use fresh, high-quality fuel mixed with the correct ratio of oil.
- Store the saw properly: When storing the saw for extended periods, drain the fuel tank and run the engine until it stalls. This will prevent fuel from gumming up the carburetor and damaging the ignition system.
- Regularly inspect the ignition system: Perform a visual inspection of the wiring, coil body, and spark plug wire at least once a month.
- Replace the spark plug regularly: A worn or fouled spark plug can put extra strain on the ignition coil. Replace the spark plug every 50-100 hours of operation.
Data Point: According to a study by the American Society of Agricultural and Biological Engineers (ASABE), regular maintenance can extend the lifespan of small engines by up to 50%.
Case Study: A Real-World Ignition Coil Rescue
I remember one particularly challenging job where we were cutting concrete for a new pipeline installation. Our TS420 was the workhorse of the operation, but on the second day, it just wouldn’t start. We were on a tight deadline, and every minute of downtime was costing us money.
After a quick visual inspection, I suspected the ignition coil. We performed a spark test, and there was absolutely no spark. I didn’t have a multimeter with me, so I couldn’t perform a resistance test. But based on the lack of spark, I was confident the ignition coil was the culprit.
Luckily, I had a spare ignition coil in my truck (always be prepared!). I quickly replaced the coil, adjusted the air gap, and the saw fired right up. We were back in business in less than an hour.
This experience reinforced the importance of carrying spare parts and knowing how to diagnose and repair common problems in the field. It saved us a lot of time and money, and it kept the project on schedule.
Beyond the Ignition Coil: Other Potential Culprits
While the ignition coil is a common cause of starting problems on the Stihl TS420, it’s not the only possibility. Here are a few other potential culprits to consider:
- Spark plug: A fouled or worn spark plug can prevent the engine from starting.
- Fuel system: A clogged fuel filter, a dirty carburetor, or a faulty fuel pump can prevent fuel from reaching the engine.
- Compression: Low compression can make it difficult or impossible to start the engine.
- Kill switch: A faulty kill switch can prevent the engine from starting.
- Flywheel key: A sheared flywheel key can throw off the ignition timing and prevent the engine from starting.
Troubleshooting Tip: If you’ve replaced the ignition coil and the engine still won’t start, systematically check these other potential causes.
Global Considerations: Adapting to Different Environments
As a logger and wood processor, I’ve worked in various environments around the world, from the temperate forests of North America to the tropical rainforests of Southeast Asia. Each environment presents unique challenges for equipment maintenance.
- Humidity: High humidity can accelerate corrosion and damage electrical components. In humid environments, it’s especially important to keep the engine clean and dry and to use dielectric grease on all electrical connections.
- Altitude: At high altitudes, the air is thinner, which can affect the fuel-air mixture and make it difficult to start the engine. You may need to adjust the carburetor settings to compensate for the altitude.
- Dust and debris: Dusty environments can clog air filters and damage engine components. Regularly clean the air filter and the engine to prevent problems.
Actionable Tip: When working in extreme environments, consider using a high-quality air filter and fuel filter to protect the engine from damage.
Sustainable Logging and Firewood Prep: A Responsible Approach
As stewards of the land, it’s our responsibility to practice sustainable logging and firewood preparation techniques. This means harvesting timber responsibly, minimizing waste, and protecting the environment.
- Sustainable harvesting: Selectively harvest trees to promote forest regeneration and biodiversity. Avoid clear-cutting large areas of forest.
- Minimize waste: Use efficient cutting and splitting techniques to minimize wood waste. Utilize wood scraps for kindling or other purposes.
- Protect the environment: Avoid operating equipment near streams or wetlands. Use biodegradable chain oil to minimize pollution.
- Season firewood properly: Season firewood for at least six months to reduce moisture content and improve burning efficiency. This reduces emissions and prevents creosote buildup in chimneys.
Data Point: Properly seasoned firewood has a moisture content of less than 20%, which results in cleaner burning and higher heat output.
Mastering the Trade: Continuous Learning and Skill Development
The world of logging and firewood preparation is constantly evolving. New tools, techniques, and best practices are emerging all the time. It’s important to stay up-to-date on the latest developments and to continuously improve your skills.
- Attend workshops and seminars: Participate in workshops and seminars offered by industry organizations and equipment manufacturers.
- Read trade publications: Subscribe to trade publications and websites that cover logging and firewood preparation.
- Network with other professionals: Connect with other loggers and firewood producers to share knowledge and experiences.
- Experiment with new techniques: Don’t be afraid to try new techniques and tools to improve your efficiency and productivity.
- Prioritize safety: Always prioritize safety when operating equipment and handling wood. Wear appropriate personal protective equipment (PPE) and follow safe work practices.
Personal Commitment: I’m always looking for ways to improve my skills and knowledge. I regularly attend workshops and seminars, read trade publications, and network with other professionals in the industry.
Final Thoughts: Keeping Your TS420 Cutting Strong
The Stihl TS420 is a reliable and powerful tool, but like any piece of machinery, it requires regular maintenance and occasional repairs. By understanding the ignition system and following these 5 Pro Hacks, you can diagnose and repair ignition coil problems quickly and efficiently.
Remember, prevention is always better than cure. By keeping the engine clean, using fresh fuel, and regularly inspecting the ignition system, you can minimize the risk of ignition coil failure.
And finally, always prioritize safety when operating equipment and handling wood. Wear appropriate PPE and follow safe work practices.
Key Takeaways:
- A faulty ignition coil can cause starting problems and reduced engine power.
- Perform a visual inspection, spark test, air gap adjustment, and resistance test to diagnose ignition coil problems.
- Replace the ignition coil if it’s faulty, using the correct part and following the proper procedure.
- Prevent ignition coil problems by keeping the engine clean, using fresh fuel, and regularly inspecting the ignition system.
- Prioritize safety when operating equipment and handling wood.
Next Steps:
- Review your Stihl TS420’s service manual for specific information on the ignition system.
- Gather the tools and supplies needed to diagnose and repair ignition coil problems.
- Practice the troubleshooting and repair procedures on a non-operational TS420 (if available).
- Share these tips with other loggers and firewood producers.
By mastering these techniques, you’ll be well-equipped to keep your Stihl TS420 running strong for years to come. Now get out there and make some sawdust!
