Why Doesn’t My Chainsaw Start?

Our machines may be reliable, but they do breakdown sometimes. Take the chainsaw, for example. An issue that appears to plague chainsaw users from time to time is its inability to start. This could be due to the user simply forgetting to fill the tank with gasoline. Or it may be because a particular part has worn out. If you should ever be confronted with a chainsaw that won’t start, here is how to troubleshoot the problem.


The very first thing you should check if your chainsaw doesn’t start is its gas tank. If it’s empty, fill it with fuel. If there is fuel in the tank and yet the machine still doesn’t start, then it’s possible that the fuel is bad. Components in gasoline can evaporate over time. If you haven’t used your chainsaw for a fairly long period of time, then the fuel may fail to ignite the engine. If this is the case, drain the fuel and fill the tank with fresh fuel.


Another problem of which you may not be aware is the fuel mixture. Two-stroke engines that are used on chainsaws require a mixture of oil and gasoline to work properly. The oil provides needed lubrication for the engine. Don’t use boat or automobile oil or any gas mixture that includes methanol or ethanol. Those mixtures can damage the engine. There is not a generic ratio of gasoline to oil for chainsaws. So review the owner’s manual for the proper ratio for your machine.


Some chainsaws require you to push a primer bulb or fuel pump to start the engine. However, overdoing this could be causing your problem.  If you smell gasoline while trying to start the engine, then this is a sign that the engine is flooded.


Check the spark plug. It is recommended that you remove it, clean it and inspect it to assure that it still works properly. If it does, re-place it into the machine. If it appears damaged, then buy a new one. In addition, check the plug for moisture. If you find it, then this too can be a sign that the engine is flooded.  Open the spark plug hole facing away from you and let the extra fuel drain out.  Deactivate the choke and pull the starter cord six to eight times as you press in the throttle control. Dry out the spark plug and refit it back into the machine.


The ignition coil should be checked next. It is the coil that sends the voltage to the spark plug when the chainsaw is started and while it is running. Test the ignition coil with a coil tester to determine if it is defective. If it is, replace it.  Another thing to consider when inspecting the ignition coil is the rewind spring. This device is supposed to reel in the starter rope after it’s been pulled and released. If the rewind spring is not functioning correctly, then the starter rope cannot recoil onto the pulley, making the process of starting the chainsaw difficult, if not downright impossible.   You can purchase a new rewind spring or you can acquire a new recoil starter assembly that includes the spring.


Inspect the carburetor. This is necessary because old fuel stored too long in the chainsaw can clog the carburetor. That’s because as the light element of the fuel evaporates, a thick substance will remain and it is this substance that causes the clogging. Remove the carburetor and use a carburetor cleaner on it to remove the residue, then replace the carburetor. There also may be some thick and sticky substance on the chainsaw. Clean that up too. It is essential that you cover the carburetor throttle with tape when you clean the chainsaw. If cleaning the carburetor doesn’t help, then it’s best to replace the entire carburetor.


If the machine still won’t start, then the air filter may be dirty. Clogged air filters may draw more gasoline than air. Running a chainsaw with a clogged air filter can increase the amount of carbon deposits as the engine produces unburned fuel. Constantly idling the engine can contribute to carbon build up. Whenever you use your chainsaw for more than five hours, remove the air filter and clean it with soap and water before re-installing it into the machine.


Next, inspect the starter rope to see if there is enough tension.  If the rope is just loose, tighten it. If it is damaged, replace it.


What If The Chainsaw Won’t Stay Running?


If your chainsaw starts okay, but doesn’t keep running, check the spark arrestor to determine if it is clogged. The spark arrestor is a fiberglass part that is inside the engine and has a small screen that prevents sparks from coming off the engine. It can get clogged with soot over time and this can cause the chainsaw to stall once it starts or to run rough. Remove the arrestor and clean it with a wire brush. If this doesn’t remedy the situation, then you may have to toss it and buy a new one. Keep in mind that the spark arrestor should be replaced after 25-hours of use anyway.


If you can start the chainsaw, but the chain doesn’t turn on the saw, then the clutch pads may be worn out. When the pads experience too much wear, they don’t engage the clutch drum that allows the chain to turn. If the clutch pads on your saw are too worn, it is recommended that you replace the clutch assembly.


Another reason why the chain may not be turning is the stop lever is not activated. Check it out to assure that it is disengaged first and is not the cause of your problem.


Of course, if you don’t want to fiddle around with the machine, bring it to Small Engine Express and we will troubleshoot the problem and fix it for you. We also invite you to drop off your chainsaw at one of our two stores for regular maintenance.