Here’s What To Do If Your Chainsaw Won’t Stay Running

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As unfortunate as it may be, this is a problem that everyone with a chainsaw will run into at one time or another: your chainsaw will fire, but will not idle or stay running. This can be a frustrating problem to have, though it is one that is typically an easy fix. If you know what things to check, and are even just a little bit handy, you should be able to have your chainsaw back up and running with minimal work. So, let’s go over some of the more common reasons causing chainsaws to stop running, as well as how to fix them. 

So, why won’t your chainsaw stay running? There are three components to keeping a gas engine running: spark, fuel, and air. If any one of these is missing, the chainsaw will not stay running. The parts in these areas that are most likely to fail are:

  • Spark plug
  • Coil
  • Fuel filter/lines
  • Carburetor
  • Air filter

These are some of the most common problem areas on chainsaws. If there is an issue with any one of the above components, it may cause your chainsaw to not stay running for long after it has started, if it will start at all. In this article, I’m going to discuss each one of these problems, as well as provide recommendations on how to fix them. 

Spark Problems

If you don’t have a good spark in a combustion engine, the engine will not run. Not having proper spark is an especially common problem when the chainsaw will turn over but not stay running, as the rotating assembly within the motor will turn as you pull the cable, but there is not enough spark to sustain that movement. So, let’s go over some of the more common spark-related issues that will prevent a chainsaw from running properly. 

Bad Spark Plug

As you may have guessed, the most important part related to getting proper spark is the spark plug. If this fails, the chainsaw will not stay on. The easiest way to test whether the spark plug is the source of your issues is to simply replace it. 

If the chainsaw runs well after you’ve replaced the spark plug, then you know what the issue was. If not, you’ll need to keep looking. Changing the spark plug is an excellent place to start as it is easy to do, and spark plugs are relatively inexpensive to buy. 

If you don’t have a new spark plug readily available, you can try cleaning your current one. If the spark plug is black, clean it up with a metal brush or some sandpaper. Also, make sure that the spark plug’s gap matches the specification in your chainsaw’s manual. 

Bad Ignition Coil

The next spark-related part that may be causing problems is the ignition coil. The ignition coil is responsible for delivering a charge to the spark plug, giving it the power that it needs to create a spark and lite the air-fuel mixture in the combustion chamber. If the ignition coil fails, the spark plug will not fire, and the chainsaw will not run. 

According to Hunker, an ignition coil’s function can be checked by removing it from the head of the engine and pulling the starter cable while looking at the spark plug. If you see a blue spark between the two nodes on the end of the spark plug, then your ignition coil is working fine. If you don’t see a spark, replacing your ignition coil may solve the problem. 

Fuel Problems

After spark-related issues, the next most common source of problems with chainsaws is the fuel system. If the engine is not being delivered fuel in sufficient quantity, or perhaps not at all, it will not run properly.

This is another great place to look for issues if the chainsaw will start but not run for long, as the fuel system may leak just a bit of fuel into the combustion chamber, but not be strong enough to deliver enough fuel to keep the engine running.

Below are some of the most common fuel-related problems that will prevent a chainsaw from running. 

Not Enough or Bad Gas

If your chainsaw has been sitting for a while, the gas in it may have either evaporated or gone bad, both of which will prevent your chainsaw from running correctly. One of the easiest fixes for a non-running chainsaw is to look in the fuel tank, and give it some fuel if the tank is empty.

If there is gas in the tank that has been sitting for more than a few months, it may have gone bad and is causing your chainsaw to not run properly. 

Clogged Fuel Filter and/or Lines

The fuel filter is responsible for filtering the fuel before it enters the engine. This is an important job, as it will prevent your engine from consuming any particulates or contaminants that are in the fuel and/or fuel tank. 

Over time, the fuel filter can become clogged, and prevent the passage of fuel into the engine. This can be checked by removing the filter and visually inspecting it for any significant blockages. If it looks okay, then it probably is, but it may be wise to replace it anyway, as fuel filters are cheap, and a visual inspection may not reveal the problem even if there is one. 

Similarly to the fuel filter, the fuel lines can also be clogged. These can be checked easily by removing and looking through them to see if there is any obstruction. If there is no visible obstruction, the fuel lines are probably not the problem. If there is an obstruction, remove it if possible, or get all new fuel lines.  

Bad Carburetor

Having a carburetor problem is one of the most frustrating and difficult issues to have out of the ones that are listed here. This is because carburetors are a pain to rebuild and are expensive to replace entirely. 

The easiest way to know if your carburetor is the problem is to exhaust all other options. If you try everything else on this list and still can’t get your chainsaw running, you may want to start looking into giving a carburetor rebuild a try. It’s not terribly difficult if you know what you’re doing, but it does take some time and is an involved process.

For more information, Sears offers a fairly comprehensive guide on carburetor rebuilds.   

Air Problems

The final piece of the internal combustion puzzle after spark and fuel is, of course, air. Air is needed in a combustion chamber to make an engine run, and if it is absent, the engine will not work.

The air intake system in chainsaws is relatively simple and is not likely to be the cause of many problems, if any, at all, but there is one piece that is worth checking if you can’t get your chainsaw to stay running. 

Clogged Air Filter

A clogged air filter can prevent a chainsaw from running properly, just as a clogged fuel filter can. If the air filter is obstructed as a result of old age and particulate build-up, it can prevent the passage of air into the engine, not allowing it to run. 

To check your air filter, remove it and perform a visual inspection. If the filter is dark and seems to have collected a fair amount of debris and/or particles, it is probably wise to clean or replace it. If it appears clean and is close to white in color (or whatever color it was originally, most commonly white or yellow), then it is probably not the source of your problems.

Final Thoughts 

A faulty chainsaw is not only an inconvenience to diagnose and fix, but it is also a hindrance to productivity. Luckily though, chainsaws are simple machines, and when they don’t work, it is usually the result of a simple problem. Looking at the components above is a great place to start diagnosing your issue, and will more than likely lead you to a solution. 

Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!