Your STIHL string trimmer won’t start for these 13 causes!

An outside trimmer is a must if you want to give your house a finished look. It may trim grass around obstacles including water features, ditches, and confined walkways.

You won’t be in any immediate danger if your string trimmer breaks, but you won’t be able to maintain a neat lawn either.

A STIHL string trimmer won’t start if the choke is adjusted wrong, the air filter, fuel filter, fuel line, carburetor, fuel tank vent, spark arrestor, spark plug, starter recoil, fuel mixture, or gasoline is old. It will also not start if any of these things are true.

In addition, a flooded STIHL engine may refuse to start. Read on to discover other factors that could prevent the trimmer from starting.

String Strimmer
String Strimmer

Common Problems With Starting a STIHL String Trimmer

It seems like you turned the choke knob the wrong way. Check the location of the choke knob to see if that helps the STIHL string trimmer start. The choke is used to restrict airflow when starting a cold engine.

Remedy: Close the choke while starting a cold motor. If the engine is already heated, the choke must be in the open position. Adjust the choke to the open position after starting a cold engine with the choke closed. In the absence of this adjustment, the motor will soon perish.

A string trimmer from STIHL will not start if the air filter is clogged.

The motor’s air intake is protected by the air filter against debris. Even a little bit of dirt or debris can cause serious problems for a motor.

Lack of regular maintenance, such as cleaning or replacing the air filter, can lead to a complete shutdown of airflow. Because of the decreased airflow, your STIHL trimmer may refuse to turn over.

Maintaining routine filter checks can help you avoid this problem in the future. To clean the filter, take it apart and follow the steps below. A broken or highly dirty filter should be replaced immediately.

STIHL string trimmers should never be used with a clogged air filter or without one at all. It’s like buying insurance against dirt wearing down the motor.

The problem can be fixed by exposing the air filter and either cleaning it or replacing it. In the event that the dirty air filter prevents the trimmer from starting, it should be changed.

How to Clean the Air Filter on a STIHL String Trimmer:

Close the choke knob to prevent dirt from falling into the carburetor throat.

  • Remove the cap protecting the air filter.
  • Get the dust and dirt out from around the air filter.
  • It’s time to remove the filter.
  • Lightly tapping the filter on your palm will loosen debris and allow it to fall out of the filter. The use of an air compressor is permitted if absolutely necessary. If the filter becomes severely clogged with dust or is broken, you should replace it.
  • Changing the filter should be done.
  • Filter housing must be reassembled.

It is impossible to start a STIHL string trimmer with a broken spark plug.

The spark plug is another annual replacement part for your STIHL string trimmer to ensure peak performance. The engine may not start if the spark plug is clogged and cannot deliver a spark.

FIX: Clean the area surrounding the spark plug with a damp cloth before attempting to remove it. Check the plug to see if it is in good shape. Spark plugs that have turned an exceptionally dark color, are worn, or are broken should be replaced.

In most cases, a spark plug can be reused after being cleaned using a wire brush. If I could, I would just get a new one. It’s a cheap yet crucial part for keeping your STIHL string trimmer running well.

Verify that the electrode gap is at STIHL’s recommended settings. Make sure the spark plug is securely fastened after installing it. (You can keep using the trimmer by disconnecting the spark plug wire.)

Problems Kickstarting a STIHL String Trimmer Caused by Using the Wrong Fuel Mix

If you try to start your motor with unleaded gas, it could seize up due to a lack of lubrication. Never use regular gas in your STIHL string trimmer.

You will definitely ruin the motor and have to replace the trimmer if you do this. Get the facts on how to mix gas and oil for STIHL string trimmers and choose the right gas. Make use of a fuel blend of gas and oil of this type.

2-Cycle Gas to Oil Mix STIHL

A 50:1 gas-to-oil mix ratio is required for all STIHL string trimmers. This is also true for STIHL 2-cycle motors and STIHL 4-MIX motors.

Mixture1 Gallon Gas2 Gallon Gas2.5 Gallon Gas
50:12.6 oz Oil5.2 oz Oil6.4 oz Oil
STIHL String Trimmer Gas to Oil Fuel Mix

When mixing the oil and gas mixture, use unleaded gasoline with an octane value of 89 or higher (mid-grade) and no more than 10% ethanol by volume. Toss in a 2-cycle premium oil that has been approved by ISO-L-EGD and JASO M345 FD.

Make sure the mixture is correct in the gas can before using the string trimmer. Two-cycle oil, such STIHL High Performance or STIHL HP Ultra, is what the company recommends.

STIHL 2-Cycle Pre-Mixed Fuel

A great strategy to lessen the likelihood of fuel issues and prolong the life of your engine is to switch to a gasoline blend that does not contain ethanol. This oil and fuel mixture has no ethanol and may be used in a string trimmer immediately.

Following this part, you will not have to deal with the drawbacks of ethanol use. It’s also helpful to have gas available whenever you need it. The 50:1 premixed fuel options of TruFuel and STIHL MotoMix are also solid choices.

FIX: you need first drain the fuel tank and then replace it with the correct amount of gas and oil. Whether the issue persists, you should have a small motor technician take a look at it to see if it can be fixed affordably.

Trouble Starting a STIHL String Trimmer on Old Fuel

The optimal use of newly purchased gas is within the first 30 days. It’s important to keep in mind that gas can start to degrade after that point.

Sticky deposits and varnish in a STIHL string trimmer can be caused by using old fuel. A damaged carburetor or clogged fuel filter could prevent the engine from starting.

Ethanol, an alternative fuel made from plants with a high starch content, such as maize, is now found in most gasoline on the market. Environmentally friendly ethanol may be bad for the trimmer’s little engine.

Premature deterioration and fuel restrictions are the results of this substance’s ability to absorb moisture from the air.

Use only unleaded gasoline with an octane rating of 89 or higher (the equivalent of mid-grade) and no more than 10% ethanol. (E10). Never put E15 or E85 in your engine because doing so will damage it and will most likely violate the warranty. These fuels have between 15% and 85% ethanol concentrations.

Applying a gasoline stabilizer will help prevent your fuel blend from degrading too rapidly. Stabilizers can be found in many 2-cycle lubricants, including STIHL’s motor oil blends.

Fuel stabilized with STIHL fuel treatment should be used within 30-60 days.

The varnish buildup can also be treated with Sea Foam Motor Treatment. This product does more than just keep gas fresh for up to two years; it also cleans and dehumidifies the fuel system.

FIX: Solve this problem by getting rid of the old gas in your string trimmer. Put the oil and gas together in the fuel tank. Compound with Sea Foam Motor Treatment.

The gasoline mixture needs time to circulate through the system, so let the string trimmer run while using it. Check for other gasoline-related problems, such a clogged fuel filter or a clogged fuel line, if you’re still having starting problems after refueling.

A STIHL string trimmer won’t start if the priming bulb is broken.

A string trimmer won’t start if the priming bulb can’t be filled with fuel because it’s damaged.

It’s likely that a clogged fuel filter or fuel line is to blame if the priming bulb checks out but the engine still won’t fire up.

FIX: The issue can be fixed by using a new priming bulb.

A STIHL string trimmer will refuse to start if the fuel filter is clogged.

The fuel tank is where you’ll find the STIHL string trimmer’s gasoline filter. Before the fuel is picked up, it is filtered through this filter. Its job is to prevent foreign matter, such dirt and debris, from entering the fuel system.

Like the air filter, the fuel filter will eventually become clogged if it is not regularly replaced. The fuel filter should be checked regularly and replaced yearly at the very least.

In the event that you find that your fuel is contaminated, you may need to drain the tank, refill the fuel, and replace the fuel filter. If dirt builds up in the gasoline filter, less petrol will make it through to the fuel lines. This could stop fuel from getting to your STIHL engine, making it inoperation

FIX: Find the clogged fuel filter inside the gasoline tank and replace it. If the fuel is dirty as well, you should change it out.

  • Remove the fuel cap and wipe the area surrounding it to make sure there is no loose dirt that could enter the tank with the fuel.
  • Changing the filter’s gain. In order to “fish” the filter out of the tank, all you need is a clean, bent wire.
  • Take out the worn-out fuel filter. Don’t loose the ring that secures the line to the filter.
  • Insert the new fuel filter and fasten the gas line to the filter with the retention ring.
  • Take off the fuel cap and change the filter in the gas tank.

If the fuel line in your STIHL string trimmer gets clogged, you may have trouble starting the machine.

An old fuel film can form in your string trimmer, preventing fuel from flowing. The string trimmer may have trouble starting if the gasoline line becomes clogged.

FIX: A clogged, kinked, or otherwise broken fuel line is the root of many string trimmer problems.

If the vent in the gasoline tank of your STIHL string trimmer is clogged, starting the machine will be difficult.

A gas tank’s vent allows fresh air to enter the tank. In the absence of a vent, the fuel tank will develop a vacuum that will prevent gas from entering the string trimmer.

Symptoms of a faulty fuel tank vent include your STIHL trimmer running for a few minutes before turning off and refusing to start again until you remove or loosen the fuel cap to permit air into the fuel tank.

If the string trimmer dies after being left to run with the top tightly fastened, and won’t start again unless the cap is undone, the fuel vent is probably clogged.

FIX: The gasoline vent must be cleaned or replaced.

Clogged carburetors prevent the STIHL String Trimmer from starting.

The carburetor adjusts how much gas is fed to the cylinder along with the air for burning. Clogged and unusable carburetors are a direct result of using old, gummed-up fuel.

FIX: Clean your carburetor if you’re good with machines. Disassemble the carburetor and spray on some carburetor cleaner.

After thorough cleaning, if the carburetor still doesn’t function properly, you may need to have it rebuilt or replaced.

An issue with starting your STIHL string trimmer could be caused by a malfunctioning recoil starter.

You can use a recoil to kickstart the motor of your STIHL string trimmer. Possible causes of non-functioning starting recoil include a broken pulley, a broken or missing spring, or broken clips.

FIX: Replacement of the spring and restringing of the recoil may solve the problem. When the clips or pulley of your recoil are worn or broken and the mechanism no longer works, it is best to replace the entire recoil assembly.

If you’re having trouble starting your STIHL string trimmer, it could be due to a malfunctioning spark arrestor.

There is a spark arrestor in your STIHL string trimmer that prevents it from starting. A spark arrestor, which is essentially a little screen attached to the muffler, is there to stop sparks and flamable debris from flying out of the trimmer and causing injury or a fire.

The spark arrestor is prone to becoming clogged with soot. When this happens, trying to turn on the string trimmer is futile.

FIX: Remove the spark plug boot to fix the problem. Wait for the muffler to cool off. Take off the spark arrestor, gaskets, and cover screen from the muffler. Use a wire brush to clean the screen of the soot. Do a fresh installation.

If you drop your STIHL string trimmer into water, it might not start.

People who tried to start their string trimmers but failed have brought them in for servicing. Usually, a flooded motor is to blame for this rather harmless occurrence.

Overfilling the carburetor can happen if the choke is closed and the starter rope is pulled repeatedly.

Other causes include repeatedly pulling the starter rope when the switch is off and repeatedly pushing the priming bulb.

FIX: To “unflood” your string trimmer and restore the correct fuel-to-air ratio for starting and running the motor, follow the instructions below.

Option 1: Start a Flooded STIHL String Trimmer

  • Choke should be turned all the way open.
  • The throttle can be started by pressing and holding the throttle trigger lockout and the throttle trigger, then sliding the control to the start position.
  • As a starter, you must pull the starting rope. From ten to twenty pushes may be required before this starts. The chainsaw engine will sputter at first. Keep pulling for another two or three times, and it should turn on.

Option 2: Start a Flooded STIHL String Trimmer

  • Achieving a stop by squeezing the lever.
  • Y’all must pull that spark plug out.
  • Start by pulling the rope 6–8 times.
  • Take out the dirty spark plug and replace it with a dry, clean one.
  • Choke off/open the chainsaw before you start it.

Starting Issues with STIHL String Trimmers and Solutions 

Wrong Choke SettingTo prevent the engine from stalling, the throttle must be closed before starting a cold engine. If you want to keep your motor going after it has warmed up, you need to take out the choke.
Old FuelNew fuel should be used if the old gasoline is older than 30 days. Use a gas stabilizer to prevent your gas from deteriorating.
Incorrect FuelDrain the gas. Use a 50:1 ratio of gas to oil in your STIHL string trimmer’s 2-cycle or 4-MIX motor.
Plugged Air FilterTake out the air filter and give it a good cleaning. If the filter appears to be extremely soiled or broken, a new one should be installed.
Bad Spark PlugThe spark plug needed to be replaced because it was worn out. Make that the spark plug wire is snug and that the electrode gap is set properly.
Bad Fuel Tank VentIf the gasoline tank vent is blocked, then use a different fuel tank.
Plugged Fuel FilterTake off the used fuel filter and swap it out with a new one.
Weak Primer BulbIt’s important to change the priming bulb because it’s broken.
Clogged, Dry, or Cracked Fuel LineEliminate the barrier by clearing the gasoline line obstruction. In the event that the line is dry or damaged and the blockage cannot be removed, a replacement should be sought.
Dirty CarburetorTake apart the carburetor so it may be cleaned. The carburetor assembly should be repaired or replaced if any of its parts are broken.
Bad Recoil StarterOne of the strings or the spring on the recoil starter has to be repaired or replaced. Recoil starters require replacement if they are ever broken.
Plugged Spark ArrestorTake off the spark arrestor from the exhaust muffler. Then, after giving it a once-over with a wire brush, put it back in place. Fix the spark arrestor that has failed.
Flooded ChainsawTo get the chainsaw going again once the excess fuel was drained, use one of the methods described above.