13 Reasons Your STIHL Chainsaw Won’t Start: Chainsaw Starting Problem

A STIHL chainsaw won’t start when it isn’t getting sufficient air, fuel, or spark

This may be due to a plugged air filter, plugged spark arrestor, clogged fuel line, plugged fuel tank vent, plugged fuel filter, dirty carburetor, bad spark plug, faulty ignition coil, or old fuel.

Remove the spark plug wire before performing repairs. The fuel tank can be under pressure. Wait for the tank to cool and then remove the cap slowly to release pressure.

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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.

Reasons a STIHL Chainsaw Won’t Start (Chainsaw Starting Problems)

1. Bad Switch or Wrong Setting

The on/off lever must be placed in the correct starting throttle position to start your chainsaw. The throttle trigger lockout must be pressed down while squeezing the throttle trigger to move the lever.

There are two throttle settings to start a STIHL chainsaw.

• START A COLD ENGINE: The position furthest from the off position is used when the engine is cold. This is the position where the choke is engaged to restrict airflow.
• START A WARM ENGINE: The other position is the starting throttle position to start the saw when the engine is already warm. The “I” position is the normal running position and the “0” position is to stop the engine.

To move between settings, you must first move the lever to the choke throttle starting position in order to move to the starting throttle position.

Each time, you must depress the throttle trigger lockout and press the throttle trigger to move the lever between positions.

SOLUTION:

How to Start a Cold Engine on a Chainsaw

• Press the primer bulb until you just begin to see fuel in the primer bulb.
• Use the throttle closed position and pull the starter rope until the engine starts.
• Move to the starting throttle position as soon as it fires. (Not moving from the closed throttle position to the starting throttle position quickly enough could result in a flooded engine causing the engine not to start).
• Once the engine begins running, immediately depress the throttle trigger lockout and blip the throttle trigger so it returns to idling speed. The starting lever will move to the “I” normal running position.

A Faulty Switch or Bad Ground

A faulty switch or bad ground wire can be the reason a chainsaw won’t start. Use a multimeter to test the switch. Replace a bad switch. Repair or replace a bad ground.

2. Old Fuel

Gas lasts a relatively short period of time before it begins to break down and become less effective. Most gasoline today has an alternative fuel added to it to make it a little better for the environment.

This fuel, made of corn or another high-starch plant, is known as ethanol. While ethanol is usually okay to run in most vehicles, it is not good for small engines like the one in your chainsaw.

Negative effects of ethanol:

• Ethanol attracts moisture from the air to the fuel system.
• The ethanol and water mixture will leave behind a sticky varnish that can gum the fuel system and cause clogs and failures.
• Water and ethanol separate from gas and is highly corrosive.

STIHL chainsaws require gasoline and oil mixed at a ratio of 50:1. Use a gas that has a minimum octane rating of 89 and a maximum ethanol content of 10%.

STIHL recommends using their STIHL 2-cycle oil and consuming fuel within 60 days. Using it within 30 days is best.

Tips for selecting fuel:

• Purchase fresh fuel and consume it within 30 days.
• Use a gas with a minimum 89 octane rating and maximum 10% ethanol content.
• Avoid gas with high levels of ethanol content like those sold as E15 and E85 as these have up to 15% and 85% ethanol content respectively.
• Mix gas and 2-cycle oil at a 50:1 ratio before adding it to the fuel tank.
• Add a fuel additive to keep fuel stable if you purchase more fuel than you can consume in 30 days.

Read more about the gas to use in your chainsaw in This is the Type of Gas and Oil STIHL Chainsaws Use.

SOLUTION: Drain oil fuel and add fresh fuel.

• Remove the fuel cap by lifting the lock lever and turning the cap counter-clockwise 1/8 of a turn to slowly release pressure before removing the cap. (If you experience significant venting, tighten the cap and wait for the tank to cool to reduce injury).
• Drain the old fuel from the tank.
• Fill a fuel can with fresh gas and oil 50:1 mixture.
• Add a fuel additive like Sea Foam Motor Treatment or STA-BIL to help reduce moisture and clean the fuel system.
• Mix the fuel, oil, and additive by placing the cap on the fuel can and gently shaking.
• Add the mixture to the fuel tank.
• Start the saw and allow the treated fuel to work its way through the fuel system.

3. Incorrect 2-Cycle Oil Mix

As I mentioned before, STIHL chainsaws require a fuel that is made up of a mixture of gas and oil. Placing straight gas in the chainsaw will damage an engine and may result in having to replace it.

Straight gas runs very dry. It can cause the engine to seize due to the lack of lubrication so the chainsaw won’t start.

Mix gas with a premium 2-cycle engine oil like High Performance, HP Ultra, or any other equivalent oil that is ISO-L-EGD and JASO M345 FD certified.

Ethanol-free fuel

Because ethanol in fuel negatively affects the performance you receive from your chainsaw, using an ethanol-free fuel is best, but more costly. A pre-mixed fuel is ready to pour into the fuel tank.

This is a great option to have sitting on the shelf so you don’t run out of fuel and have to make a trip to the fuel station and then have to spend time mixing oil into the fuel.

MotoMix 2-cycle pre-mixed fuel is a stable fuel good for up to 2 years. This is the product I use in my chainsaw when I store it for extended periods.

SOLUTION: Drain the wrong fuel mixture from the chainsaw and add fresh gas and oil mixture at a rate of 50:1.

4. Clogged Air Filter

The air filter is an important component used to protect your engine. A filter keeps dust and debris from passing through the filter and into the carburetor throat causing wear on the engine.

When the air filter isn’t regularly cleaned or replaced, the buildup of dirt can be so significant that good airflow isn’t able to pass through it. A plugged air filter can make it difficult to start your chainsaw.

It’s good practice to replace your air filter annually and clean it several times throughout the season for the average homeowner. If you use your chainsaw a lot, you’ll have to clean and replace the filter more often.

Never run your chainsaw without an air filter. You may get tempted to run your chainsaw just a little longer to finish your task until you get a new air filter replacement, but doing so puts the engine at risk of damage.

STIHL uses various air filters depending on the work conditions and model of your chainsaw. I have listed the cleaning instructions for a couple of common types of filters.

Refer to your operator’s manual if you are unsure of the type of air filter you are using on your chainsaw and its cleaning procedure.

SOLUTION: Replace an air filter that is very dirty or damaged. Clean a filter that is lightly dirty and in good condition.

Clean a 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 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 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.

5. Bad Spark Plug

The spark plug provides the spark required to start and keep the chainsaw running. The spark plug is a wear item that should be changed annually for the casual user.

If you use your chainsaw regularly, you may need to change it as often as monthly.

SOLUTION: Inspect the spark plug and clean it with a wire brush in between replacements. A dirty spark plug can cause the spark plug to misfire causing running issues.

Replace a spark plug if you find it is very dark in color, has a burnt electrode, or has broken porcelain. Make sure the spark plug is gapped to STIHL’s specification and the spark plug wire is securely attached.

6. Faulty Ignition Coil

If the spark plug is in good condition, but you still aren’t getting spark, check the ignition coil. The winding on the ignition coil can separate and short out and your chainsaw won’t start

When this happens, the spark plug won’t get the voltage required to create a spark. This will cause your chainsaw to fail to start.

SOLUTION: Identify a bad ignition coil using an ohmmeter to check for a break in continuity. Replace the ignition coil if you find a break.

7. Clogged Fuel Filter

Like the air filter is used to keep dirt out of the air intake to prevent wear on the engine, the fuel filter is used to keep dirt out of the fuel system.

The fuel filter on a chainsaw is located in the fuel tank. It is attached to the end of the fuel line to strain fuel before it enters the fuel system.

When the filter isn’t changed regularly or when dirty fuel has been used, it can become plugged restricting the amount of fuel that is able to pass through the filter.

A chainsaw that isn’t able to get a sufficient supply of fuel will fail to start or it may begin to run sluggishly. Replace the fuel filter annually and more often if you use the chainsaw often.

SOLUTION: Replace a chainsaw fuel filter

• Wipe around the fuel cap to keep any dirt from falling into the fuel tank when removing the fuel cap.
• Remove the fuel cap by lifting the locking lever and turning about 1/8 of a turn to allow the cap to vent. If you find there is a lot of venting, reseal the cap and allow the tank to cool. Once cool, remove the cap by turning it counter-clockwise and remove the cap.
• Use a clean bent wire to hook the fuel line and pull the fuel filter out of the tank.
• Hold the fuel line with a pair of needle nose pliers. Pull the filter out of the fuel line. Don’t let go of the fuel line and drop it back in the tank.
• Install a new fuel filter by inserting the male end into the fuel line making sure it is secured to the fuel line.
• Place the filter in the fuel tank and reinstall the fuel cap.

8. Bad Primer Bulb on a Chainsaw

A cracked primer bulb that won’t fill up with fuel won’t function correctly to get fuel to the carburetor.

SOLUTION: Replace with a new primer bulb.

9. Clogged or Punctured Fuel Line

Letting fuel sit in your chainsaw for a long time can leave behind a substance that builds up in the fuel line restricting fuel flow. You can try to remove the blockage and clean the line using a carburetor cleaner.

SOLUTION: Remove the clogged line from the chainsaw and spray carburetor cleaner into the line to loosen up the clog. Blow compressed air through the line to remove the clog.

If you are unable to successfully remove the blockage or you find the fuel line is damaged, punctured, or cracked, it’s best to replace it with a new fuel line.

10. Dirty Carburetor

The carburetor regulates the amount of fuel that is mixed with air to create combustion in the cylinder. Old fuel will gum up and clog the carburetor so it no longer functions as designed. This can keep your STIHL from starting.

SOLUTION: If you are a little mechanical you should be able to handle cleaning your carburetor. Clean the carburetor by taking it apart and using carburetor cleaner to clean it.

If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor. STIHL only sells parts through an independent dealer.

11. Bad Recoil Starter

Your chainsaw uses a recoil to start the engine. A bad pulley; loose or missing spring; or broken clips can keep your recoil from working.

SOLUTION: You can attempt to replace the spring and restring the recoil. If it does not work because other components in your recoil are damaged, such as the clips or the pulley, you are better off just replacing the recoil assembly.

12. Plugged Spark Arrestor

The spark arrestor is a small screen in the muffler that can get plugged with soot. A plugged spark arrestor will prevent airflow causing your chainsaw not to start.

SOLUTION: Remove the spark arrestor and clean it with a wire brush. Replace the mesh spark arrestor screen when you are not able to clean it sufficiently or if it is damaged.

Never run your chainsaw without this screen or with a screen that has a hole in it. Without a screen, hot material can come out of the saw potentially starting a fire or causing burns.

13. Flooded Engine

The engine can become flooded when the choke is in the closed position and the starter rope was pulled many times.

It can also happen with the switch off and the starter rope is pulled multiple times or when the primer bulb is pushed too many times.

How to Fix a Flooded Engine on a STIHL Chainsaw

• Switch the lever to the “0” stop position.
• Remove the spark plug.
• Pull the starter rope 6 to 8 times.
• Reinstall the clean dry spark plug.
• Start the chainsaw in the starting throttle position.