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10 Reasons STIHL Leaf Blower Loses Power & Bogs Down

Your blower isn’t giving you the power it once did. It no longer blows leaves and other debris as it once did. I’ve put together a list of common problems to troubleshoot the loss of power.

A STIHL leaf blower loses power and bogs down when the engine isn’t getting sufficient fuel, air, or spark. This can be caused by a plugged filter, clogged fuel line, faulty fuel tank vent, bad spark plug, plugged spark arrestor, or dirty carburetor.

Before working on your STIHL blower, make sure the engine is not hot and you follow all safety precautions to prevent injury. You can find these safety precautions listed in your operator’s manual.

Reasons a STIHL leaf blower is losing power:

  • Old gasoline
  • Dirty carburetor
  • Plugged air filter
  • Dirty spark plug
  • Plugged fuel filter
  • Clogged fuel line
  • Plugged fuel tank vent
  • Plugged spark arrestor
  • Plugged cooling system
  • Carbon buildup on the exhaust port

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Follow all safety instructions provided in your equipment operator’s manual prior to 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.

10 Reasons Your STIHL Leaf Blower Has No Power

1. Old Gas Will Cause Your STIHL Blower to Have No Power

All gas is not the same. Learning about how gas impacts your STIHL blower’s performance to minimize fuel and engine problems.

Negative effects of gasoline on your STIHL blower:

Most gas sold today contains ethanol. This alternative fuel is made from renewable resources like corn and other high-starch plants.

Ethanol is used because it is better for the environment, however, it is not good for small engines. It attracts moisture from the air. When this moisture collects in the fuel system, it can cause corrosion.

Ethanol and water will leave behind varnish and gummy deposits that restrict fuel flow by clogging the fuel lines and carburetor. This mixture is corrosive to the fuel system.

Most people don’t realize that gas can go bad pretty quickly. It’s best to consume the amount of fuel you purchase within 30 days and no longer than 60 days when using a stabilizer.

Adding a fuel stabilizer like Sea Foam Motor Treatment can help keep fuel stable longer and reduce moisture.

Right Fuel to Use in Your STIHL Blower:

STIHL offers leaf blowers with 2-cycle or 4-MIX engines. These engines require a gas and 2-cycle engine oil mixed at a 50:1 ratio. This means you need to mix 50 parts gas with 1 part oil.

Because of the harmful effects of ethanol, you must use unleaded gasoline with a minimum 89-octane rating (mid-grade) and a maximum ethanol content of 10% (E10) in your STIHL blower.

Mix with a premium 2-cycle oil from STIHL like STIHL High Performance or STIHL HP Ultra. You may also use a 2-cycle oil that is ISO-L-EGD and JASO M345 FD certified. Read more about the right fuel for your STIHL leaf blower in This is the Gas and Oil STIHL Leaf Blowers Use.

SOLUTION: Drain the old fuel remaining in your leaf blower and fill it with fresh fuel. Add a fuel stabilizer like Sea Foam Motor Treatment to stabilize the fuel, reduce moisture and clean the fuel system.

2. Dirty Carburetor Will Cause Your STIHL Blower to Lose Power

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 properly.

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 remove buildup.

If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor.

Depending on the model leaf blower you own, the age of the blower, and the price of the carburetor, it may be best to invest in a new leaf blower rather than put money towards replacing a carburetor on an old blower.

3. Plugged Air Filter Will Cause Your STIHL Blower to Have No Power

When the air filter becomes plugged with the dirt and debris that gets tossed in the air from running a leaf blower, it will restrict airflow.

It may have so much dirt buildup that air isn’t able to pass through the filter at a sufficient rate causing your STIHL to lose power.

To prevent running into this problem, replace your air filter once a year and clean it several times throughout the lawn care season.

SOLUTION: If you find your STIHL air filter is plugged, I recommend replacing the filter. A filter is usually not very expensive. It is an important component when it comes to protecting the engine.

STIHL uses many different types and sizes of air filters depending on the model and type of leaf blower you use. An excessively dirty or damaged filter should be replaced.

If you choose to clean your filter, follow the tips below for a common STIHL filter. Refer to your operator’s manual if you are unsure of the type of filter on your blower and its cleaning instructions.

Clean a STIHL leaf blower air filter:

  • Close the choke so dirt doesn’t fall into the carburetor throat.
  • Remove the air filter cover and remove the air filter.
  • Wipe out any dirt or debris remaining in the air filter cover or housing.
  • Tap the filter against a solid surface or your hand to knock the dirt out of the filter.
  • Install the clean filter. (Replace a very dirty filter or one that is damaged with a new air filter).
  • Reattach the air filter cover.

4. Dirty Spark Plug Will Cause Your STIHL Blower to Have No Power

A fouled spark plug can cause your STIHL blower to lose power due to intermittent spark.

A damaged spark plug or one that is dark in color due to being excessively dirty must be replaced. If your spark is in good condition and a little dirty, remove the dirt using a wire brush.

I recommend replacing your spark plug annually to help minimize spark plug issues throughout the season. A spark plug is an inexpensive maintenance part. You can run into power loss problems with your STIHL without a good spark plug.

SOLUTION: Remove the spark plug and replace the plug when you find it is dirty or damaged. Make sure the new spark plug is gapped to the manufacturer’s specification. Most STIHL blowers require an electrode gap of 0.02 in (0.5 mm).

Securely attach the spark plug wire (boot) so it makes a good connection. A loose wire can cause your blower to fail to start, stop running or lose power.

5. Plugged Fuel Filter Will Cause Your STIHL Blower to Have No Power

The purpose of the fuel filter on your STIHL blower is to screen the fuel as it enters the fuel line to prevent dirt and other debris from being introduced into the fuel system.

When the fuel filter isn’t changed out regularly, the filter can become plugged.

This will restrict the amount of fuel that is able to pass through the filter which can be the reason you begin to experience a loss of power when operating the blower. When the engine doesn’t get enough fuel, it will bog down.

Solution: Replace a fuel filter that isn’t allowing gas to pass through it and into the fuel line. The fuel filter is located in the fuel tank. To get to the filter, first, wipe the area around the fuel cap to remove dirt and debris to prevent it from falling inside the tank.

Pull the fuel filter out of the tank. A clean bent wire works well for this. Remove the filter from the fuel line.

Insert the new fuel filter into the fuel line and secure the fuel line to the filter using the retaining ring. Place the filter inside the fuel tank and install the fuel cap.

6. Clogged Fuel Line Will Cause Your STIHL Blower to Have No Power

The fuel line can become restricted with gummy deposits left behind from using old fuel through your leaf blower. Dirt could have also gotten into the fuel system causing blockages. This can prevent a good flow of fuel to the engine resulting in power loss.

Solution: Inspect the fuel line looking for any clogs preventing fuel flow. Replace a fuel line that is clogged, kinked, or has developed cracks from age.

7. Plugged Fuel Tank Vent Will Cause Your STIHL Blower to Have No Power

The fuel tank must be vented to equalize the air pressure in the tank. When the vent is clogged on your STIHL, a vacuum will form and fuel will not be able to flow out of the tank. You will find the tank vent connected to the fuel line coming out of the fuel tank.

Solution: If your STIHL blower begins to bog down and lose power, place it on a level surface. Loosen the fuel cap and allow your blower to run.

If your blower no longer runs sluggish and loses power once the air is introduced to the fuel tank, you most likely have a plugged fuel tank vent. Replace the fuel tank vent.

8. Plugged Spark Arrestor Will Cause Your STIHL Blower to Have No Power

The spark arrestor is a small metal screen that prevents hot exhaust material from leaving the muffler and starting a fire. When this small screen becomes plugged, your STIHL blower may experience a loss of power where it won’t run at full RPMs.

Solution: Disconnect the spark plug wire. Make sure your engine is not hot. Remove the engine cover and the engine exhaust cover. Carefully remove the spark arrestor screen. Clean the screen with a wire brush.

Install the clean screen, and attach the engine exhaust cover and engine cover. Reattach the spark plug wire.

If the screen isn’t able to be sufficiently cleaned or you find it is damaged or has a hole in it, replace it with a new spark arrestor screen.

9. Plugged Cooling System on a STIHL Leaf Blower

The small engine on the blower uses air to keep it cool. When it overheats, the engine can lose power and possibly damage it.

SOLUTION: Keep the cooling system clean by removing dirt and debris from the air intake, flywheel, cooling fins, and engine cover.

10. Carbon Buildup on the Exhaust Port Will Cause STIHL Blower to Lose Power

The exhaust port located behind the muffler can develop carbon deposits that can cause your leaf blower running problem.

SOLUTION: This area should be checked and cleaned by a STIHL servicing dealer. Attempting to clean it yourself may damage the blower.

When to Have a Mechanic Repair Your STIHL Leaf Blower?

If you have checked the items listed above for your lack of power problem and this didn’t solve your problem, it is time to have a professional mechanic diagnose and repair your STIHL leaf blower.

You may also not feel comfortable performing repairs on your blower. That is okay. That’s why there are small engine mechanics at your local STIHL dealership to assist you.

Keep in mind the labor rate for the mechanic to diagnose your problem. There is typically a flat rate charge to diagnose the problem and then add labor and parts fees in addition to the fee to make the repairs.

This may not make sense if you are running an old inexpensive leaf blower on its last leg. Keep this in mind so you don’t get surprised when you get a diagnostics bill for a leaf blower that may not be worth repairing.

Having your STIHL leaf blower repaired by a mechanic is a personal decision that only you can make. You have the weigh the reliability, quality, and age of your current leaf blower against the cost to repair it and the cost to purchase a new leaf blower.