Don’t let a stubborn chainsaw ruin your day. If your chainsaw won’t start, it’s usually a simple fix related to fuel, spark, or air. We’ll walk you through the most common reasons and easy solutions so you can get back to cutting safely and efficiently.
There’s nothing more frustrating than pulling the starter cord on your chainsaw, only to be met with silence. You’ve got a job to do – maybe it’s clearing fallen branches after a storm, cutting firewood for the winter, or just tidying up your property. But when your chainsaw refuses to fire up, it can feel like a brick in your hands. Don’t worry, though. As someone who’s spent more time with chainsaws than I care to admit (and made every beginner mistake along the way!), I can tell you that most starting problems are surprisingly common and usually have straightforward solutions.
We’ll break down the most likely culprits, from the fuel you’re using to the spark plug and air filter. We’ll cover what to check, how to check it, and what you can do yourself to get that engine roaring again. Let’s get your chainsaw running!
Common Chainsaw Starting Problems: The Big Three
Think of your chainsaw’s engine like your own body. It needs the right “food” (fuel), a “spark” to get going, and it needs to be able to “breathe” (air). If any of these are off, it just won’t run.
When a chainsaw won’t start, it almost always boils down to one of these three things:
- Fuel System Issues: The engine isn’t getting enough clean fuel, or the fuel isn’t getting to the cylinder.
- Ignition System Issues: The spark plug isn’t creating a spark, or the spark isn’t happening at the right time.
- Air System Issues: The engine can’t get enough air to mix with the fuel, or the air is too dirty.
We’ll dive into each of these, but first, let’s cover a couple of crucial preliminary checks that can save you a lot of time.
Before You Start Troubleshooting: The Basics
Sometimes, the fix is so simple you’ll kick yourself. Before we get into the nitty-gritty, let’s make sure you haven’t overlooked the obvious:
1. Is the Kill Switch On?
This sounds silly, but I’ve seen it happen. Most chainsaws have a safety lever or switch that, when in the “off” position, prevents the engine from starting. Make sure your kill switch is in the “run” or “on” position. It’s usually a toggle or slider near the handle.
2. Is There Enough Fuel?
Again, obvious, but essential. Check your fuel tank. Make sure you’re using the correct fuel-to-oil mixture for a two-stroke engine. Using straight gasoline or the wrong oil ratio can cause starting problems and damage your engine. Always refer to your owner’s manual for the recommended mixture. For most modern chainsaws, it’s a 50:1 ratio (50 parts gasoline to 1 part high-quality 2-stroke oil).
Tip: Use fresh fuel. Gasoline can go stale, especially if it contains ethanol, which can absorb moisture and degrade over time. If your gas has been sitting for more than a month, it’s best to drain it and refill with fresh fuel.
3. Is the Choke Set Correctly?
The choke restricts airflow to the carburetor, creating a richer fuel mixture needed for starting a cold engine. Most chainsaws have a manual choke. When the engine is cold, the choke should be in the “on” or “choke” position (usually closed or pulled out). Once the engine starts and runs for a few seconds, you need to move the choke to the “off” or “run” position (open or pushed in) to allow more air in. If you forget to move the choke, the engine will likely flood and die.
What if the engine is warm? If you’ve just shut the chainsaw off and are trying to restart it while it’s still warm, you typically don’t need the choke, or you might need to use a “half-choke” setting. Trying to start a warm engine with the choke fully engaged will almost certainly cause it to flood.
Troubleshooting Fuel System Issues
The fuel system is where many starting problems originate. Let’s break down the common culprits:
1. Clogged Fuel Filter
The fuel filter sits inside the fuel tank and prevents debris from entering the carburetor. Over time, it can become clogged with dirt or fuel varnish.
- Symptoms: Engine starts but runs rough, sputters, or dies under load. May not start at all if severely clogged.
- How to Check: You’ll need to access the fuel tank. Locate the fuel line running from the tank to the carburetor. The filter is usually attached to the end of this line inside the tank. You might be able to pull it out with a pair of long-nosed pliers or by carefully tipping the tank.
- Fix: If the filter looks dirty or clogged, replace it. They are inexpensive and readily available at any power equipment dealer or online.
2. Clogged Fuel Lines
Similar to the filter, fuel lines can become blocked by debris or dried fuel residue.
- Symptoms: Similar to a clogged fuel filter – poor running or no start.
- How to Check: Disconnect the fuel line from the carburetor (after ensuring the fuel tank is off or the line is clamped to prevent leakage). Try to blow gently through the line. If you can’t, or if it feels restricted, it’s likely clogged.
- Fix: You can try to clean them with compressed air or a small, flexible wire, but often it’s easier and more reliable to replace the fuel lines.
3. Dirty or Clogged Carburetor
The carburetor is the heart of the fuel system, mixing fuel and air. It has tiny passages that can easily get clogged by stale fuel, dirt, or varnish.
- Symptoms: Engine hard to start, idles poorly, hesitates when you give it throttle, or won’t run at all.
- How to Check: This is a bit more involved. You’ll need to remove the carburetor from the chainsaw. Once removed, you can try to clean it.
- Fix:
- Carburetor Cleaner: The easiest DIY fix is to use a spray can of carburetor cleaner. Remove the carburetor, spray the cleaner into all the openings and passages, and let it sit for a while. You can also use a soft brush or a fine wire to gently clean out any visible gunk.
- Ultrasonic Cleaning: For a more thorough cleaning, especially if the carburetor is heavily gummed up, an ultrasonic cleaner can be very effective.
- Rebuild Kit: If cleaning doesn’t work, you might need to rebuild the carburetor using a rebuild kit, which includes new gaskets, diaphragms, and needles.
- Replacement: If all else fails, or if the carburetor is damaged, you may need to replace it entirely.
Important Note on Fuel: Stale fuel is a major culprit for carburetor issues. Always use fresh gasoline and the correct 2-stroke oil mix. Consider using a fuel stabilizer if you don’t use your chainsaw frequently. You can learn more about proper fuel handling from the U.S. Environmental Protection Agency.
4. Water in the Fuel
Moisture can get into your fuel tank, especially if you’re not storing your gas properly or if condensation forms in the tank. Water won’t ignite, and it can cause starting problems.
- Symptoms: Engine sputters, runs erratically, or won’t start.
- How to Check: Drain a small amount of fuel from the tank into a clear container. Look for any separation or cloudiness, which might indicate water.
- Fix: Drain the fuel tank completely and refill with fresh, properly mixed fuel. You might also want to clean out the fuel filter while you’re at it.
Troubleshooting Ignition System Issues
A working ignition system is crucial for combustion. If your fuel system is fine, the problem might be with the spark.
1. Faulty Spark Plug
The spark plug is a small but vital component that ignites the fuel-air mixture. It can become fouled, worn out, or damaged.
- Symptoms: No spark, weak spark, or engine misfires.
- How to Check:
- Remove the Spark Plug: Use a spark plug wrench to carefully remove the spark plug.
- Inspect: Look for signs of damage, heavy carbon buildup, oil fouling, or a corroded electrode.
- Check for Spark: Reconnect the spark plug wire to the spark plug. Hold the metal body of the spark plug firmly against a clean, unpainted metal part of the chainsaw engine (like a cooling fin). Have someone else pull the starter cord. You should see a strong, blue spark jump across the gap.
- Fix:
- Clean: If the spark plug is dirty but otherwise looks okay, you can try cleaning the electrode with a wire brush and a bit of carburetor cleaner.
- Adjust Gap: Ensure the gap between the electrodes is set to the manufacturer’s specification (check your manual). A feeler gauge is used for this.
- Replace: Spark plugs are inexpensive. If it looks worn, damaged, or you’re unsure, it’s best to replace it with a new one of the correct type.
Safety First! When checking for spark, keep your fingers away from the spark plug and the metal engine part. The electrical charge can give you a nasty shock.
2. Damaged Spark Plug Wire or Boot
The wire connecting the ignition coil to the spark plug, and the boot that covers the plug, can also fail.
- Symptoms: No spark, weak spark, or intermittent spark.
- How to Check: Inspect the wire and boot for any cracks, cuts, or signs of corrosion. Ensure the boot is securely seated on the spark plug.
- Fix: If damaged, the wire and boot may need to be replaced. This is often part of the ignition coil assembly.
3. Faulty Ignition Coil
The ignition coil generates the high voltage needed to create the spark. If it fails, you won’t get a spark.
- Symptoms: No spark at all, even with a new spark plug.
- How to Check: This is harder to diagnose without specialized tools. If you’ve confirmed the spark plug, wire, and fuel system are okay, the ignition coil is a likely suspect.
- Fix: The ignition coil will need to be replaced. This is a more advanced repair and might be best left to a service center if you’re not comfortable.
Troubleshooting Air System Issues
An engine needs air to run. If the air supply is restricted or contaminated, it won’t start or will run poorly.
1. Clogged Air Filter
The air filter prevents dust and debris from entering the engine’s crankcase and carburetor. A dirty air filter can severely restrict airflow.
- Symptoms: Engine hard to start, runs sluggishly, or dies when you try to accelerate.
- How to Check: Locate the air filter cover (usually a knob or screws on the side of the engine). Remove the cover and take out the air filter.
- Fix:
- Clean: Most air filters can be cleaned. For paper filters, you can often tap them gently to remove loose debris or use compressed air (blow from the inside out). For foam filters, wash them with warm, soapy water, rinse thoroughly, and let them dry completely before reinstalling.
- Replace: If the filter is heavily soiled, damaged, or a paper filter that can’t be cleaned effectively, replace it with a new one.
Importance of a Clean Air Filter: A clean air filter is vital for engine performance and longevity. Always clean or replace your air filter regularly, especially when working in dusty conditions. You can find guidelines on air filter maintenance in your chainsaw’s user manual or resources from manufacturers like STIHL.
2. Clogged Carburetor Air Intake
Less common, but the opening where air enters the carburetor can also get blocked.
- Symptoms: Similar to a clogged air filter.
- How to Check: With the air filter removed, visually inspect the intake port on the carburetor for any obstructions.
- Fix: Remove any debris carefully.
When to Seek Professional Help
While many chainsaw starting problems are DIY-friendly, there are times when it’s best to call in the experts:
- You’ve tried everything: If you’ve gone through all the common checks and your chainsaw still won’t start, there might be a more complex issue.
- Engine Damage: If you suspect internal engine damage (e.g., a seized piston), don’t try to force it.
- Ignition System Complexity: Diagnosing a faulty ignition coil or flywheel issues can be tricky without the right tools and knowledge.
- You’re Uncomfortable: If you’re not comfortable with the steps involved, it’s always safer to take it to a qualified small engine mechanic.
Remember, safety is paramount. If you’re unsure about any step, it’s better to err on the side of caution.
Troubleshooting Table: Quick Reference
Here’s a handy table to help you quickly diagnose common starting issues:
| Symptom | Possible Cause | What to Check | Likely Fix |
|---|---|---|---|
| No sound, no crank | Kill switch off, no fuel, dead spark plug, ignition failure | Kill switch, fuel level, spark plug | Correct switch, add fuel, replace spark plug, check ignition coil |
| Engine cranks but won’t fire | No spark, no fuel, flooded engine | Spark plug, fuel filter, choke position | Check spark, clean fuel system, adjust choke |
| Engine starts but sputters/dies | Clogged fuel filter/lines, dirty air filter, incorrect fuel mix | Fuel filter, air filter, fuel quality | Clean/replace filter, check fuel mix |
| Engine runs poorly, lacks power | Clogged air filter, dirty carburetor, incorrect fuel mix | Air filter, carburetor, fuel quality | Clean/replace air filter, clean carburetor, check fuel mix |
Frequently Asked Questions (FAQs)
What is the most common reason a chainsaw won’t start?
The most common reasons a chainsaw won’t start are issues with the fuel system (stale fuel, clogged filter, or dirty carburetor) or the ignition system (a fouled or dead spark plug).
How do I know if my chainsaw has a flooded engine?
A flooded engine occurs when too much fuel enters the combustion chamber, preventing ignition. You might smell a strong odor of gasoline. If you try to start it and it just cranks without firing, especially after using the choke, it’s likely flooded. The fix is to turn off the choke, open the throttle fully, and pull the starter cord several times to clear the excess fuel.
Can I use regular gasoline in my chainsaw?
No, you should never use regular gasoline alone in a two-stroke chainsaw. Two-stroke engines require a specific mixture of gasoline and 2-stroke oil. Using straight gasoline will cause severe engine damage. Always check your owner’s manual for the recommended fuel-to-oil ratio (commonly 50:1).
How often should I replace my chainsaw’s spark plug?
It’s a good practice to inspect your spark plug at the beginning of each cutting season or after about 100 hours of use. Replace it if
Samuel H. Murphy is DIY expert and Interior Designer. He is also a part time content writer of Capische. He lives in Warren city, Michigan. He test tools like drill, saw, sander, air compressor etc and helps readers to find out the best tools.