Outdoor equipment is designed to be used in some dirty conditions, including the chainsaw. Dirt and wood chips get tossed into the air when felling a tree.
Even though it is designed to withstand some rugged conditions, without proper maintenance a chainsaw can begin to lose power or fail to start.
A chainsaw won’t start when it doesn’t get sufficient air, fuel, or spark.
This can be due to a plugged air filter, clogged fuel line, plugged fuel filter, dirty carburetor, bad spark plug, faulty ignition coil, bad recoil starter, or old fuel.
Keep reading for other reasons that can cause a chainsaw to not start including a flooded chainsaw. Take all safety precautions prior to working on your chainsaw including making sure the switch is in the off position and the spark plug boot is removed.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
Troubleshoot a Chainsaw Starting Problem (Engine Won’t Start)
1. Bad Switch or Wrong Choke Setting
You will have an on/off switch on a chainsaw that must be placed in the correct starting position. The switch will control the choke setting on some chainsaw models, while other chainsaws will use a separate on/off switch and choke lever.
No matter what brand of chainsaw you use, you must have the choke on to start a cold engine. The choke restricts air to allow more fuel to reach the engine to start it.
Once the engine is warm, the choke must be placed in the off position so the chainsaw continues to run. If you are unsure how to engage your chainsaw’s choke, refer to your operator’s manual.
A faulty switch or bad ground wire can also be the reason a chainsaw won’t start. You can use a multimeter to test the switch. Replace a bad switch. Repair or replace a bad ground.
2. Old or Bad Fuel
Old gas can cause many problems in the chainsaw including starting issues. Gas can become less effective and begin to break down as quickly as 30 days after purchase.
An alternative fuel known as ethanol is added to most of the fuels on the market today. This is a plant-based fuel that makes fuels a little environmentally friendly.
While ethanol is safe to use in most vehicles today, it is not good for a small engine like the one used in a chainsaw. Ethanol attracts moisture to the fuel system.
This mixture of water and ethanol will leave behind a sticky varnish over time that can gum the fuel system. This can cause restrictions that keep the chainsaw from getting sufficient fuel and may no longer start.
Because gasoline begins to degrade soon after purchase, it’s important to use gas within 30 days. If you are unable to consume it this quickly, add a fuel additive to stabilize the gas so it lasts a little longer.
Not all fuel stabilizers are the same and will keep fuel stable to the same lengths of time.
You must find out more information about the stabilizer you are using and never assume it lasts longer than 30 days unless the manufacturer provides this information.
Avoid gas with high levels of ethanol content like those sold as E15 and E85 as these have up to 15% and 85% ethanol content respectively. Read more about the gas to use in your type of chainsaw here.
When you are having start problems and you find the fuel is old, empty the tank and fill it with fresh fuel.
Start the chainsaw to allow it to run through the chainsaw and work its way through the fuel system once you are able to get it started.
3. Wrong Fuel in a 2-Cycle or 4-Cycle Engine
One thing you don’t want to get wrong is the type of fuel you add to a chainsaw. Getting this wrong can cause permanent engine damage.
A majority of gas-powered chainsaws sold today use a 2-cycle engine, but you may find saws with 4-cycle engines as well.
2-Cycle Fuel Requirements:
A chainsaw with a 2-cycle engine will have a single fill port for a gas and oil mix. The gas and oil is mixed at a ratio of 50:1 or 40:1. The correct ratio depends on the manufacturer.
Here is the ratio and oil recommended by several common chainsaw manufacturers:
|Manufacture||Gas to Oil Mix||2-Cycle Oil||Premixed Fuel|
|ECHO||50:1||Echo||Red Armor Pre-Mix|
|Poulan Pro||50:1||Poulan Pro|
|Stihl||50:1||Stihl||Moto Mix Pre-Mix|
To create the gas and oil mixture, use gasoline with a minimum octane rating of 89 and maximum ethanol content of 10%. Mix gas with premium 2-cycle engine oil that is ISO-L-EGD and JASO M345 FD certified.
NEVER run straight gas through a chainsaw. It runs very dry and can cause the engine to seize due to the lack of lubrication. A mistake like this could result in having to replace your chainsaw with a new one.
4-Cycle Engien Fuel Requirements:
Chainsaws with 4-cycle engines have separate fill ports for engine oil and gasoline. Use gasoline with a minimum 89 octane rating and a maximum 10% ethanol content.
Because ethanol in fuel negatively affects your chainsaw’s performance, using an ethanol-free fuel is best, but more costly.
While it is more costly, it is a convenient option to have sitting on the shelf so you don’t have to run out to the fuel station and mix the fuel.
4. Plugged Air Filter
An air filter is installed in a chainsaw to collect dust so the engine receives clean air. The filter keeps dirt from causing wear and damage to the engine.
When the air filter isn’t regularly cleaned or replaced, sawdust and dirt can build up on the filter preventing sufficient air from passing through the filter and into the carburetor throat.
A lack of air can make it difficult to start a chainsaw and keep it running.
It’s good practice for the average homeowner to replace the air filter each year and clean it several times throughout the season. If you use your chainsaw a lot, you’ll have to clean and replace the filter more often.
Take time to inspect your air filter to prevent overheating the engine and causing damage. I know, this is one more step but takes less than a minute to check the condition of the filter.
If the filter is extremely dirty or damaged, it must be replaced. Never run a chainsaw without an air filter.
The type of air filter used on a chainsaw will vary with each chainsaw model and manufacturer. You can find cleaning instructions for many common filters from chainsaw manufacturers in my articles on Stihl, Husqvarna, and ECHO chainsaws.
If you are unsure of the type of filter you are using and its cleaning instructions, refer to the operator’s manual.
5. Bad Spark Plug
The spark plug provides the spark required to start and keep the chainsaw running. The spark plug is a wear item that should be changed annually for the casual user.
If you use your chainsaw regularly, you may need to change it as often as monthly. Inspect the spark plug and clean it with a wire brush in between replacements.
A dirty spark plug can cause the spark plug to misfire causing running issues. Replace a spark plug if you find it is very dark in color, has a burnt electrode, or broken porcelain.
Make sure the spark plug is gapped to the manufacturer’s specification and the spark plug wire is securely attached. These things can also cause starting problems.
6. Faulty Ignition Coil
If the spark plug is in good condition, but you still aren’t getting spark, check the ignition coil. The winding on the ignition coil can separate and short out.
When this happens, the spark plug won’t get the voltage required to create a spark. This will cause your chainsaw problems.
Identify a bad ignition coil using an ohm meter to check for a break in continuity. Replace the ignition coil if you find a break.
7. Plugged Fuel Filter
The fuel filter is used to keep dirt and debris from entering the fuel system. The filter is a cylinder-shaped part that is located inside the fuel tank. You will find it attached to the fuel line.
When the filter isn’t changed regularly or when dirty fuel has been used, it can become plugged not allowing sufficient fuel to pass through the filter. This may cause the saw to fail to start or run sluggishly.
I recommend replacing the fuel filter if you are a homeowner that uses the saw for emergency situations or sparingly. If you’re using the saw regularly to cut wood, you may have to replace it as often as every 3 months.
Replace the fuel filter:
- Wipe around the fuel cap to keep any dirt from falling into the fuel tank when removing the fuel cap.
- Remove the fuel cap (allow the chainsaw to cool down first if you have been using it).
- Use a clean bent wire to hook the fuel line and pull the fuel filter out of the tank.
- Hold the fuel line securely while pulling the filter out of the fuel line. Don’t let go of the fuel line.
- Install a new fuel filter by inserting the male end into the fuel line making sure it is secured to the fuel line.
- Place the filter in the fuel tank and reinstall the fuel cap.
8. Bad Primer Bulb
A cracked primer bulb that won’t fill up with fuel won’t function correctly to get fuel to the carburetor. Replace with a new primer bulb.
9. Clogged or Punctured Fuel Line
A fuel restriction can be created when the fuel line becomes clogged. This can prevent the chainsaw from starting. Remove the clogged fuel line and use carburetor cleaner to help loosen the clog.
Spray compressed air through the line to remove it.
If you are unable to remove the clog or you find the fuel line is dry, cracked, or punctured, it’s time to replace it with a new fuel line.
10. Dirty Carburetor
The carburetor regulates the amount of fuel that is mixed with air for combustion in the cylinder. Old fuel will gum up and clog the carburetor so it no longer functions as designed. This can keep your chainsaw from starting.
If you are a little mechanical you should be able to handle cleaning your carburetor. Clean the carburetor by taking it apart and using carburetor cleaner to clean it.
If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor.
11. Bad Recoil Starter
A chainsaw uses a recoil to start the engine. A bad pulley; loose or missing spring; or broken clips can keep your recoil from working.
You can attempt to replace the spring and restring the recoil. If it does not work because other components in your recoil are damaged, such as the clips or the pulley, you are better off just replacing the recoil assembly.
12. Plugged Spark Arrestor
The spark arrestor is a small screen in the muffler that can get plugged with soot. A plugged spark arrestor will prevent airflow causing a chainsaw not to start.
Remove the spark arrestor and clean it with a wire brush. Replace the mesh spark arrestor screen when you are not able to clean it sufficiently or if it is damaged.
Never run a chainsaw without this screen or with a screen that has a hole in it. Without a screen, hot material can come out of the saw potentially starting a fire or causing burns.
13. Flooded Engine
The engine can become flooded when the choke is in the closed position and the starter rope was pulled many times.
It can also happen with the switch off and the starter rope being pulled multiple times or when the primer bulb is pushed too many times.
How to Fix a Flooded Engine
Here are a couple of options to try when starting a flooded chainsaw:
Start a Flooded Engine Option 1:
- Turn the switch on and make sure the choke is off and in the open/run position.
- Press the throttle trigger while pulling the starter rope over and over. This can take anywhere between 5 and 15 pulls before it starts. Your chainsaw engine will sputter first. Continue to pull 2 to 3 more times and it should start.
Start a Flooded Engine Option 2:
- Place the switch to the stop/off position.
- Remove the spark plug and clean it
- Pull the starter rope 6 to 8 times.
- Reinstall the clean dry spark plug.
- Turn the switch to the start/on position.
- Start the chainsaw with the choke off and in the open/run position.
Chainsaw Starting Problems & Solutions (Quick Reference Chart)
|Bad Switch or Wrong Choke Setting||Ensure the choke is on to restrict airflow when starting a cold engine. Remove the choke once the engine has warmed so it continues to run.|
Replace a bad switch or bad ground wire.
|Old Fuel||Replace fuel that is older than 30 days with fresh fuel.|
|Incorrect Fuel||Drain the fuel. Use a gas and oil mixture in chainsaws with 2-cycle engines. 4-cycle engines require a straight gas.|
|Plugged Air Filter||Remove a plugged air filter and clean it. Replace the filter with a new one if it is very dirty, wet, or damaged.|
|Bad Spark Plug||Replace a bad spark plug. Make sure the electrode gap is correct and the spark plug wire is securely in place.|
|Faulty Ignition Coil||Replace a bad ignition coil.|
|Plugged Fuel Filter||Remove the old filter from the fuel tank and install a new fuel filter.|
|Weak Primer Bulb||Replace a cracked primer bulb.|
|Clogged, Dry or Cracked Fuel Line||Remove a clogged fuel line and remove the restriction. Replace a fuel line if the clog can’t be removed or the line is dry or cracked.|
|Dirty Carburetor||Remove and clean the carburetor. Rebuild any damaged parts or install a new carburetor assembly.|
|Bad Recoil Starter||Replace the spring and restring the recoil starter. Replace the recoil starter when it is damaged.|
|Plugged Spark Arrestor||Remove the spark arrestor from the muffler. Clean it using a wire brush and reinstall it. Replace a damaged spark arrestor.|
|Flooded Chainsaw||Fix this by using one of the methods above to remove excess fuel and start the chainsaw.|
Still Having Troubles With Your Chainsaw?
As a chainsaw owner, you’re going to run into problems with it occasionally. This is true of all chainsaws.
To help you quickly identify the cause of your problem and how to fix it, I’ve put together a handy reference guide.
You will find charts with problems and solutions to many common issues along with links to information in more detail.
Check out Common Chainsaw Problems for help solving problems with your equipment not starting, the chain not turning, the engine dying, a loss of power, and more.