12 Reasons Your Stihl Chainsaw Starts, Stalls and Dies (FIXED)

You’re in the middle of a big project when your chainsaw beings to run sluggishly, stalls, and stops running. Running old gas can be a big culprit, but many other items can cause a Stihl to die.

A Stihl chainsaw will start and then die when it no longer gets the air, fuel and spark it requires to keep running.

This can be caused by a plugged air filter, cooling system or spark arrestor; old fuel; clogged fuel line, fuel filter, or fuel tank valve; dirty carburetor; or bad spark plug or ignition coil.

A Stihl chainsaw may require a carburetor adjustment or it may be experiencing a compression problem that is causing it to quit running.

Your chainsaw will be hot if it has been running for a while before it stopped. Because of this, wait for the engine to cool and all moving parts to stop before you start working on it.

Beware that the fuel tank can be under pressure. Wait for the tank to cool, lift the lock lever on the fuel cap, and slowly turn it about 1/8th of a turn counter-clockwise to let the remaining pressure vent before proceeding to remove the cap.

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

12 Reasons Your Stihl Chainsaw Starts Then Dies

1. Plugged Air Filter

The air filter is an important component to run on your Stihl chainsaw. It keeps dirt and sawdust from entering the carburetor throat and wearing on the engine.

You never want to run your chainsaw without an air filter. Doing so will put the engine at risk of permanent damage.

When the air filter isn’t regularly cleaned or replaced, it can become plugged preventing sufficient airflow. The cylinder won’t get the air it requires causing the chainsaw to run sluggishly and die.

It’s best to replace the air filter annually for the average homeowner and inspect it frequently throughout the year to clean or replace it if necessary. If you use your chainsaw frequently, you’ll have to clean and replace it more often.

Here are instructions to clean a couple of types of Stihl air filters. Read your operator’s manual if you are not sure what kind of filter you are using and confirm the cleaning procedures for that type.

Clean a Stihl chainsaw FLEECE air filter:

• Remove the cover.
• Clean around the air filter to remove any dirt and sawdust.
• Remove the air filter.
• Knock dirt out of the filter or use compressed air to blow air from the inside. DO NOT use a brush.
• If the filter is very dirty, wash it in a mild dish detergent and water solution, and rinse from the inside outward until the water runs clear.
• Allow the filter to completely air dry. DO NOT use heat on the filter as this can damage it. DO NOT apply oil to the filter.
• Reinstall the clean filter.
• Purchase and install a new air filter if the old filter is extremely dirty or damaged
• Reattach the cover.

Clean a Stihl chainsaw HD2 air filter:

• Remove the cover.
• Clean around the air filter to remove any dirt and sawdust.
• Remove the air filter.
• Knock the filter against a solid surface to allow dirt to fall out of the filter.
• Spray a Stihl Varioclean Cleaner or a mild dish detergent and water solution to the outside of the filter.
• Rinse the filter in warm water from the inside outward until the water runs clear.
• Allow the filter to completely air dry. DO NOT use heat on the filter as this can damage it. DO NOT apply oil to the filter.
• Reinstall the clean filter.
• Purchase and install a new air filter if the old filter is extremely dirty or damaged
• Reattach the cover.

2. Plugged Cooling System

Your Stihl chainsaw runs an air-cooled engine. This means air is what cools the engine. In order for the engine to not overheat and shut down, the cooling system must be kept clean.

Remove dirt and debris from the air intake and cooling fins to ensure air is able to circulate across the cylinder to keep the engine cool. To do this, first, remove the spark plug and wait for the engine to cool.

Remove the engine cover and remove debris from the cover and around the outside of the cylinder.

Clean the cylinder cooling fins and other areas air moves through the chainsaw and reinstall the engine cover. Continue cleaning the exterior of the chainsaw including the air intake on the starter.

3. Plugged Spark Arrestor

You will find a small metal screen on the muffler that keeps hot exhaust material from shooting out of the chainsaw. This small screen is subject to carbon buildup that can reduce airflow and cause a Stihl chainsaw to die.

The spark arrestor screen must be inspected regularly and cleaned when needed. Begin by removing the spark plug wire. Then remove the exhaust cover to access the spark arrestor screen.

Carefully remove the spark arrestor screen. Clean the screen with a metal brush. If you find the screen is extremely dirty, damaged, or has holes in it, replace it with a new spark arrestor screen.

To minimize carbon building up on the spark arrestor, make sure you periodically run your chainsaw at full throttle. Letting your chainsaw idle or run at low speeds for a long time will contribute to a buildup of carbon.

4. Old Fuel

Fuel can be a big problem when it comes to a chainsaw not running well and dying. Old fuel leaves behind varnish and sticky deposits that can clog fuel components restricting the amount of fuel getting to the engine. This can cause the saw to shut off.

Before checking your fuel, make sure you allow the saw to cool. The fuel tank can be under vapor pressure while hot. Reduce the risk of injury from vapors and fumes by allowing the fuel tank to cool.

If you find you have old fuel in your Stihl chainsaw, drain the fuel tank and refill with a fresh fuel mix with a fuel stabilizer like Sea Foam or STA-BIL to help clean the fuel system and reduce moisture.

Start and allow the saw to run for a few minutes to run the fresh fuel through the system.

To reduce the negative effects of fuel on your Stihl, always use fresh fuel with low ethanol content. Make sure the fuel is made up of gasoline and oil mixed at a ratio of 50:1.

Here are a few tips for selecting and caring for fuel:

• Only use fresh fuel. Fuel can begin to degrade as quickly as 30 days after purchase.
• Use a 50:1 gas-to-oil mixture in your 2-cycle Stihl chainsaw.
• Select gasoline with a minimum octane rating of 89 and a maximum ethanol content of 10%.
• Mix in a premium 2-cycle oil that is ISO-L-EGD and JASO M345 FD certified.
• Add a fuel stabilizer. To prevent gas from breaking down so it lasts a little longer, uses a fuel stabilizer. Many oils include a fuel stabilizer. It can last anywhere from 30 days to 2 years.
• Consume fuel quickly. Stihl recommends consuming fuel within 30 days and no longer than 60 days.

Read more about fuel selection and care in “This is the Type of Gas and Oil Stihl Chainsaws Use“.

5. Plugged Fuel Filter

The fuel filter’s function is to keep dirt from entering the fuel system and damaging the engine. The fuel filter is a small cylinder-shaped part located inside the fuel tank.

You will find it attached to the fuel line. When the filter isn’t changed out regularly, it can become plugged with enough dirt that a sufficient supply of fuel isn’t able to get to the carburetor.

Inspect the filter and replace it if needed. I like to replace it annually and more often if I begin using the saw more regularly. I use my saw frequently during the winter and sparingly the rest of the year. I typically change the fuel filter before and after the winter season.

Change a Stihl chainsaw fuel filter:

• First, wipe around the fuel tank cap so dirt doesn’t fall into the tank.
• Pull the filter out of the tank using a filter hook or a clean bent wire.
• Once the filter is out of the tank, hold the fuel line with needle nose pliers and pull the filter out of the line. Don’t let go of the fuel line.
• Insert a new fuel filter into the line. Make sure the filter is securely attached to the fuel line.
• Place the fuel filter inside the tank.
• Reinstall the fuel cap.

6. Clogged or Punctured Fuel Line

Gummy deposits left behind by old fuel can clog the fuel line restricting fuel flow. When you find a clogged fuel line, remove it from the chainsaw and clean it to open the line.

Spray carburetor cleaner into the line to loosen the clog. Follow this with compressed air to dislodge and remove the clog. Repeat as necessary to remove the clog.

If you can’t remove the clog or you find the fuel line is dry and cracked, you need to replace the fuel line with a new line of the same diameter and length.

Also, replace any line that has a puncture. A punctured fuel line can draw air into the fuel system resulting in a chainsaw running sluggish because too much air is being introduced to the cylinder.

7. Plugged Fuel Tank Vent

The fuel tank on a Stihl chainsaw must be able to vent to allow air to pass. When the tank isn’t able to vent, vacuum forms that will prevent fuel from leaving the tank to the carburetor. The chainsaw will bog down or stop running.

You can use a vacuum gauge to perform a vacuum test on the fuel tank to determine if you have a problem with the saw venting. There shouldn’t be a vacuum. The atmospheric pressure and the fuel tank pressure should be the same.

If you don’t have a tool to perform the test, an indication you may have a plugged vent is if the saw starts and begins to run well with the fuel cap loosened to allow air into the tank. (Be careful when loosening the cap as the tank may be under pressure).

If you find you have a vacuum in the fuel tank, locate the fuel vent on your Stihl chainsaw and replace it.

8. Dirty Carburetor

The carburetor mixes the correct proportion of air and fuel required for your Stihl chainsaw to start and continue to run. The passageways can become clogged and the small components can fail to function correctly which can be the reason the chainsaw stops running.

Old fuel is a big reason why a Stihl carburetor will stop working. You may be able to clean or rebuild your carburetor to get it working again. You will have to replace the carburetor if this doesn’t work.

9. Carburetor Needs Adjustment

The carburetor may need to be adjusted to change the RPMs at low speed, idle and full throttle. There are adjustment screws on the carburetor to make these adjustments.

The screws are labeled “H” for high speed, “LA” for idle speed, and “L” for low-speed.

Set Stihl carburetor adjustment screws to standard setting:

Begin the carburetor adjustment by placing the “H” and “L” adjustment screws at their original standard settings. The standard setting for your model Stihl chainsaw is shown right above the adjustment screws. This setting varies by model.

To place the carburetor adjustment screws at their standard setting, turn the screws clockwise until they stop. Then turn each screw counter-clockwise with the number of turns indicated above the screw.

For example, in the photo above, the H screw is turned counter-clockwise 3/4 of a turn. The L screw is turned counter-clockwise one full turn. Again, this may be different for your model Stihl saw.

Adjust “L” low-speed screw:

Start the saw and let the chainsaw idle. Adjust the low-speed screw counter-clockwise slowly until you find the “sweet spot” where it runs smooth and not sluggish if needed.

Adjust “LA” idle screw:

Next, while the chainsaw is idle, make sure the chain is not moving. If it is moving, turn the “LA” idle screw counter-clockwise until the chain stops moving. Then continue to turn it counter-clockwise 1/4 turn further.

If your saw dies at idle, turn the idle screw clockwise until the chain just starts to move. Then turn the screw counter-clockwise 1/4 turn.

Adjust “H” high-speed screw:

Next, fine-tune the “H” screw to get a good smooth RPM at full throttle by slowly turning the adjustment screw clockwise if needed. Don’t over-adjust and allow the RPMs to increase too much or you will damage the engine.

Stihl does have some limits to the adjustments you can perform to the carburetor. If you are continuing to have problems with the carburetor, bring your chainsaw to your local Stihl dealer.

10. Bad Spark Plug

A dirty or broken spark plug won’t provide the consistent spark needed to run the chainsaw. It may provide intermittent spark causing the saw to lose power and possibly die.

Inspect the condition of the spark plug tip. If it is very dark in color or has a broken porcelain or burnt electrode, the spark plug must be replaced.

You can try to clean the spark plug with a wire brush and reuse it if it’s just a little dirty. I prefer to just replace it. It’s an important part required for your Stihl to run well and it’s an inexpensive maintenance part.

Make sure the spark plug gap is correct and the spark plug wire is securely attached. These two items can also cause the chainsaw to shut down.

11. Faulty Ignition Coil

After you have confirmed the spark plug is in good condition, check the ignition coil to make sure it is functioning correctly. The coil provides the electrical current to the spark plug to form a spark that ignites the fuel to start and keep your chainsaw running.

When the coil gets hot, the winding on the coil can separate and short out. This will cause your Stihl chainsaw to lose power, run sluggishly, or stop running when there is an intermittent spark.

A bad ignition coil will not be able to provide sufficient voltage to the spark plug.

12. Compression Problem with the Engine

While pulling the starter recoil rope, you may notice a loss of compression. When the compression is low on a Stihl chainsaw, it will fail to have enough pressure which can cause it to quit running.

This can be the result of worn crankshaft seals, worn piston rings, or damage to the piston.

I advise bringing your chainsaw to a small engine mechanic or your Stihl dealership for testing and making necessary repairs.