Stihl MS170 Won’t Start – [Quick Fixes with Troubleshooting]

Patrick McMann

Knowledge Based

If you’re having trouble starting your Stihl MS170 chainsaw, you’re not alone. This is the most common issue out of all problems that Stihl chainsaw operators face. But don’t worry. I’ll help you resolve the “Stihl MS 170 not starting” issue to get your cutting machine up and running in no time at all.

In this article, I’ll discuss the various reasons in detail as to why your Stihl MS170 won’t start and provide solutions for each specific issue. I’ll also share the proper way to start your Stihl chainsaw. 

By the end of this article, you’ll clearly understand how to diagnose and fix the problem and start your cutting machine correctly. So, keep reading!

The Stihl MS170 chainsaw may not start due to fuel, spark plug, carburetor, or air filter issues. Regular maintenance and correct starting procedures can help resolve these common problems.

Stihl MS170 Won’t Start – What to Do?

If you are unable start your Stihl MS170 chainsaw, it could be due to fuel, carburetor, spark, clutch, vapor lock issues, or an overheated air filter. In such a case, you’ll need to find and fix problems in one of these components.

fixing stihl ms170 wont start problems

Let’s have a detailed look at the reasons preventing your Stihl cutting machine from starting up and the solutions to fix this issue:

1. Fuel Problems

If your Stihl MS170 chainsaw doesn’t have enough fuel in the tank or contains stale fuel, it may have trouble starting. Using the wrong fuel-to-oil ratio or a clogged fuel filter can also cause starting difficulties. Damaged fuel lines can be another culprit. 


Drain the old fuel and refill the tank with fresh gasoline mixed correctly with oil to fix these issues. Remember to prepare the fuel mixture only by following the manufacturer’s instructions

If the fuel filter is dirty, clean it or replace it. Additionally, inspect the fuel lines for cracks, leaks, or blockages and replace any damaged ones.

2. Spark Plug Issues

Sometimes, if the spark plug is worn-out or not working properly, it won’t create a spark, which is essential for igniting the fuel-air mixture. Even if the spark plug is fine, a damaged ignition coil or spark plug wire can result in a weak or nonexistent spark, causing starting issues. 

Moreover, if the ignition switch is faulty or out of place, it can prevent the electrical supply to the ignition system. This will make it difficult for the engine to start.


To address these problems, you can inspect the spark plug’s condition and replace it if needed. Ensure the spark plug gap aligns with the manufacturer’s specifications. 

Additionally, check the ignition coil and spark plug wire for any damage and replace them if needed. Finally, assess whether the ignition switch is functioning correctly and is positioned to “ON.” If necessary, you may need to repair or replace the ignition switch.

3. Carburetor Problems

A dirty or clogged carburetor can block the fuel flow to the engine, causing difficulties in starting. Similarly, if the carburetor settings have adjustment issues (e.g., an improper mixture of air and fuel), your Stihl MS170 chainsaw won’t start.


Clean the carburetor thoroughly, including its jets and passages, to fix these issues. If you’re unsure about cleaning, opt for professional servicing. Additionally, refer to the chainsaw’s manual or seek assistance from a professional for adjusting the carburetor.

4. Clogged or Damaged Air Filter

If the air filter is dirty or clogged, it hampers the airflow to the engine. This results in a fuel mixture that is too rich and which can make it challenging to start the engine. 


To resolve this issue, remove the air filter, clean it thoroughly, and reinstall it correctly. If the air filter is damaged, replace it.

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5. Low Compression Level

If the engine lacks sufficient compression, it can hinder the proper ignition of the fuel-air mixture, leading to difficulties in starting the engine. 


To address this issue, examine the compression levels of the engine with a compression tester. Then make any necessary adjustments to ensure optimal compression.

6. Flooded Engine

Too much fuel flooding the engine results in a rich air-fuel mixture and can make starting the Stihl 170 chain saw difficult. 


To resolve this issue, take out the spark plug and pull the starter cord multiple times. This helps clear the excess fuel from the engine. Afterward, let the engine dry before reinserting the spark plug and attempting to start the cutting machine again.

7. Vapor Lock Problem

Another reason your Stihl MS170 won’t start might be due to the vapor trapped in the fuel tank, clogging up its vents. 


Make sure you give those vents a good cleaning. The vapor will escape once you clear them out, and your chainsaw should start working again.

8. Engaged Safety Lock

Check if your Stihl MS170 chainsaw’s safety features, like chain brake or throttle lock, are active. If these safety mechanisms are engaged, your cutting machine won’t start. 


Make sure to release all safety mechanisms correctly before starting the machine.

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How to Start a Stihl MS170 Chainsaw?

If you’re having trouble starting the Stihl MS170 chainsaw, there may be nothing wrong with it. The issue might be with the way you’re starting it. To assist you, here is a step-by-step guide on the correct way to start the Stihl MS170:

Step 1: Add Fuel

To start, fill up your Stihl MS170 chainsaw’s fuel tank with the correct gasoline and oil mixture as recommended by the manufacturer. Make sure you fill the tank adequately and then remove the cutting machine’s protective sheath.

Step 2: Engage the Chain Brake

Place the chainsaw on a stable surface and engage the chain brake. It’s crucial not to skip this step as it keeps the operator safe. By turning on the chain brake, you prevent the chain from accidentally rotating while starting the chainsaw.

Step 3: Position the Switch

Find the on/off switches on your cutting tool. You’ll usually see two switches: one toggle switch near the back handle and another rocker switch close to the throttle trigger. Make sure both switches are set to the “off” position before starting the machine.

Step 4: Press the Primer Bulb

Find the primer bulb, which is usually near the fuel cap. Give it a few presses until you notice fuel filling up the bulb. This primes the carburetor and makes starting the chainsaw easier.

Step 5: Position the Choke

Find the choke lever, typically near the air filter cover. Push the lever all the way up to engage the choke and put the chainsaw in cold start mode. But here’s a tip: Before you go full throttle with the choke, make sure to press the throttle trigger first. 

You need to do that to be able to engage the choke fully. Once you’ve engaged the throttle, turn the choke to full. Then release the throttle and proceed with the following steps.

Step 6: Pull the Starter Rope

Hold the back handle tightly with one hand and use your foot to stabilize the chainsaw by placing it in the open space of the rear handle. If your chainsaw has a decompression valve, press it to release some compression, which helps with a smoother start. 

Grab the starter rope firmly with your other hand and pull it slowly until you feel some resistance. Then, give it a quick and firm pull to start the engine. It might require a few pulls before the engine starts, so be patient. Avoid pulling the rope too forcefully to prevent any injury.

Step 7: Wait For the Engine to Warm Up

After the engine starts, it might run rough at idle. To fix this, move the choke lever halfway to let some air into the carburetor and give the engine a few seconds to warm up before proceeding to disengage the choke.

Step 8: Disengage the Choke

Slowly bring the choke lever all the way down to turn off the choke. This lets the chainsaw run on a regular mixture of fuel and air.

Step 9: Disengage the Idle Setting

Give the throttle trigger a gentle squeeze to release the idle setting, and let the chainsaw rev up. Make sure you have a secure hold on the back handle while doing this.

Step 10: Deactivate the Chain Brake

After starting your Stihl 170 chainsaw, press the throttle again to set the choke to idle and deactivate the brake. Now you are ready to cut trees with your chainsaw.

Step 11: Check the Operation

Pay attention to any unusual sounds or vibrations. Check that the chain is rotating smoothly and without obstructions, and ensure the tool is operating correctly.

Frequently Asked Questions

1. What to check when my Stihl chainsaw won’t start?

If your Stihl chainsaw won’t start, here are a few things you need to check: 

  • Make sure the chainsaw has enough fuel. Always use fresh gasoline, as stale fuel can cause problems with the carburetor, making it difficult to start the engine.
  • Check the spark plug to ensure it’s clean and properly positioned. A dirty or damaged spark plug can prevent the engine from firing. 
  • Keep an eye on the air filter and clean it if it’s dirty. A dirty air filter can limit airflow and hinder the starting process. 
  • Check the carburetor. If it’s clogged, it will prevent your cutting machine from starting up. You can attempt to clean it yourself or take it to a qualified mechanic.
  • If your cutting tool has low compression, it may struggle to start. You can check the compression using a compression tester.

2. How do I know if my Stihl chainsaw is flooded?

A flooded chainsaw means there is an excessive amount of fuel in the engine, making it difficult to start. Here are some signs to recognize:

  • Your cutting machine won’t start, even after multiple attempts of pulling the starter cord.
  • You can detect the smell of gasoline emanating from the engine.
  • The spark plug may be damp or wet with fuel.
  • The engine might backfire when you try to start it.

3. How do you start a hard-starting Stihl chainsaw?

When a Stihl chainsaw is hard-starting, it means it is challenging to get it to start, even if you follow the correct starting steps. So, you’ll need to follow specific steps to start it. Here they are:

  • Check the fuel level and ensure it’s fresh to avoid carburetor issues.
  • Inspect the spark plug for cleanliness and proper gap.
  • Clean the air filter to maintain adequate airflow.
  • Prime the chainsaw by pressing the primer bulb multiple times until fuel is visible.
  • Set the choke to full position for an enriched fuel mixture.
  • Pull the starter cord slowly to build compression, then pull firmly and smoothly.
  • Listen for the engine to start, and continue pulling until it reaches full speed.
  • Release the choke once the engine is running smoothly.

4. Is there a trick to starting a Stihl chainsaw?

Yes, there are a few tricks to starting a Stihl chainsaw that will make sure your tool operates smoothly without trouble. Follow the tips below:

  • Prime the chainsaw properly by pressing the primer bulb until the fuel is visible. But avoid over-priming, as it can flood the engine with excessive fuel and make starting difficult.
  • Use the choke correctly for easier starting, setting it to full choke for cold starts and gradually moving it to the run position once the engine starts.
  • Pull the starter cord smoothly and firmly to avoid engine damage.
  • Ensure the chainsaw is in the correct starting position, on a level surface, with the chain brake engaged.
  • Allow the chainsaw to warm up for a few minutes before starting for easier engine ignition.

Final Thoughts: Fixing Stihl MS170 Won’t Start Problems

Now that you know the solutions to the issues preventing your Stihl MS170 from starting up, you can tackle these problems head-on. Remember to regularly clean and maintain your chainsaw, ensuring the fuel system is in good condition, and the spark plug and air filter are clean and functional. 

Also, follow the correct starting procedure I’ve discussed above to avoid future starting issues. Don’t let a stubborn “Stihl MS170 won’t start” problem discourage you. Take the steps mentioned above, and you’ll have your chainsaw starting up correctly in no time at all.

Patrick McMann