Chainsaw Won’t Stay Running? 5 Reasons Why and What To Do About It

Chainsaw Won’t Stay Running

We’ve all had that experience of waking up to a gorgeous day outside with no plans for the day other than yard work. We get up, drink some coffee, and go start up the lawnmower, weed wacker, and chainsaw, only to find the chainsaw won’t stay running. Why isn’t your chainsaw working?

If your chainsaw won’t stay running, it is likely due to one of the following issues: your spark plugs are failing, you have bad fuel, you have a blocked carburetor, your engine is flooded, you have a blocked idle port, or you have a fuel delivery issue. Each of these issues can be easily resolved.

When it comes to small engine machines such as chainsaws, these incredibly complex systems can be compromised without proper maintenance. Let’s take a deeper look at each of the reasons why your chainsaw isn’t working and how to fix it.

1. Your Spark Plugs Are Bad or Failing

Most chainsaws function on a gas-powered combustion engine that works similarly to how the engine in your car works. These engines rely on a small series of miniature explosions to create the energy that runs your device. A small amount of gas is combined with oxygen inside a chamber in the engine; then, a small spark ignites this gas, causing a piston to move, which creates energy.

Spark Plugs Are Bad or Failing

If this spark does not activate, however, the gas and air will not have any source of heat that causes the combustion. Spark plugs are responsible for providing this spark, so if they are damaged or covered in excess carbon dioxide, they will not function properly.

How To Fix

To resolve this issue, simply remove the spark plugs from your engine and clean them or replace them with matching spark plugs. Spark plugs are often sold online and in small engine repair shops. They are easy to replace and can be done without professional help.

2. You Have a Blocked Carburetor

As mentioned previously, if you are missing any of the three elements of combustion (air, heat, or fuel), your engine will not work. If your spark plug is damaged, for example, then your fuel won’t be able to ignite. If your carburetor is blocked, the gas will not be able to mix with the air that allows combustion. 

Blocked Carburetor

As gas evaporates from lack of use, the sticky, unreliable elements are often left in the carburetor, blocking it from mixing the oxygen and the gas. Additionally, sometimes, if your exhaust has an issue escaping, the excess carbon can block up your carburetor, preventing it from functioning correctly.

How To Fix

If this is the case, clean your carburetor using a special cleaner. Many products are sold in regular stores specially designed to clean your carburetor. Try using one of these to make your chainsaw function correctly.

3. You Have a Flooded Engine

Sometimes the process of combining the air and gasoline in your chainsaw engine does not go perfectly. If you do not have the right combination of oxygen and gas, then your engine will not be able to ignite correctly.

Flooded Engine

Sometimes, when an engine is turned off too quickly, fuel still moves into the chamber where it is supposed to ignite, making the spark plugs wet and preventing them from actually being able to spark.

How To Fix

You should use the primer button to help suck some of the fuel into the carburetor so that the gas will be able to ignite correctly in the engine. If you still manage to flood the engine, you can remove the spark plugs and, quite literally, dump out the extra fuel that is preventing your engine from igniting. 

4. You Have a Blocked Idle Port

In your carburetor, you have a number of different parts that regulate how much air is mixed with the gas to make it spark. Imagine a box with two tubes going into it and a tube going out of it. The box, the carburetor itself, is where the gas is mixed with air. One of the tubes brings the gas (the fuel line), and the other brings the air. This tube that brings the air is called the idle port.

Blocked Idle Port

If the idle port is blocked or damaged, then the air will not flow into the carburetor to mix with the gas. The idle port could be blocked by the same substances as the entire carburetor or could be damaged so air can’t flow through. In some idle ports, there is a screw that can be moved to allow more or less air into the chamber.

How To Fix

If you have a blocked idle port, you can try adjusting the screw so that you can fix the airflow problem. If this doesn’t work, you may need to remove the carburetor and spend extra time cleaning the idle port. If the idle port is damaged, you’ll need to replace it.

5. You Have a Fuel Delivery Issue

Ultimately, if your engine doesn’t receive the gas in the combustion chamber, then there will be nothing to actually power the engine.

Fuel Delivery Issue

Sometimes, fuel lines can become disconnected so that gas doesn’t flow through them. Fuel lines can also have a crack or cut that causes the gas to leak out. Other times, a clog within the fuel line prevents it from delivering gas to the chamber.

How To Fix

If you have a blocked idle port, you can try adjusting the screw so that you can fix the airflow problem. If this doesn’t work, you are in a fuel line. If there is damage to the connecting piece or the fuel line itself, replace the fuel line; otherwise, try to remove the clog or clogs.

Why Does My Chainsaw Die When I Give It Gas? 

You likely have bad fuel if your chainsaw dies when you give it gas. While most people don’t know this, gas, similar to most food products, can expire.

Gas has a number of volatile ingredients that allow it to ignite, which explains why you smell gas as soon as it is exposed to the air. But, these components of the gas can evaporate very quickly, making the gas less combustible and, eventually, unusable. 

If you have put gas in your chainsaw’s engine, but it is quickly dying, you are probably using bad fuel. Gas expires within about 8 weeks of not being used. If the gas you are adding is old, or if your chainsaw has gas and hasn’t been used in that time, you are likely working with bad fuel.

How To Fix

If this is the case, remove the gas from your chainsaw and add fresh gas. It might still take a few minutes for your chainsaw to start functioning correctly, but replacing the fuel will often solve the issue. You can also prevent this issue by starting your chainsaw every few weeks so that the gas is not left unused.

Final Thoughts

Combustion engines like chainsaws are incredibly complex systems that, if even one aspect of the system is not working, the whole system is unlikely to be successful. If you are having trouble keeping your chainsaw running, try using one of the fixes outlined above. If you still have issues, you can take your chainsaw to a small engine repair shop to fix it. 

Whenever using a chainsaw, be sure you are safe, and if you suspect damage to your chainsaw, do not use it.

About the author

Picture of David Yeoman

David Yeoman

I'm a technical writer who writes in-depth articles for readers wanting uncomplicated explanations for creative topics made difficult by industry jargon. I'm a woodworker, metalworker, landscape photographer, writer, Python and PostgreSQL programmer, and pilot. Freelance after 42 years in the corporate world, I have an MBA in Technology.

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