How do you fix a chainsaw that won't stay running?

How do you fix a chainsaw that won’t stay running?

If you’re a chainsaw user, you know that nothing is more frustrating than a chainsaw that won’t stay running. Whether you’re a professional logger or a homeowner with a few trees to trim, a chainsaw that won’t stay running can be a major inconvenience. In this ‘How do you fix a chainsaw that won’t stay running’ article, we will discuss some common causes of a chainsaw that won’t stay running and provide simple and easy steps on how to fix it.

Many issues, such as a faulty spark plug or a clogged air filter, might cause your chainsaw to cease working. Simple issues include a damaged gasoline line, contaminated fuel, and an incorrectly adjusted high-low adjustment screw. Furthermore, more sophisticated difficulties exist, such as a faulty carburetor or an engine compression problem.

The following is a list of the most typical issues that prevent a chainsaw from starting. Also included are suggestions for how to repair them and when to seek professional help.

Simple explanations for why your chainsaw won’t start

The first thing you should do is consult your chainsaw manual (available for free on this website). To help you discover the problem, make sure you grasp the fundamentals of your chainsaw. Then attempt to match the problem to one of our explanations below.


Bad Fuel or Old Gas

When was the last time you changed the oil in your chainsaw?

The volatile components of gas evaporate as it sits unused for an extended period of time, something most people are unaware of. Bad gasoline will not burn correctly, causing your chainsaw to slow down or not function at all.

Low-octane gas contains more ethanol, making it less durable than 89 octane or higher. After 8 weeks of inactivity, it becomes detrimental to the engine of your chainsaw. It deposits sediments and muck in your gasoline filter, fuel lines, or, worse, the carburetor.

If you haven’t used your chainsaw in over 8 weeks and have left gasoline in it, consider changing it. Test it with new 89 or higher octane fuel. If the fuel has been sitting for too long, your engine may be too damaged to function correctly.


Fuel Delivery Problem

Another common cause of a chainsaw that won’t stay running is fuel delivery issues. If the chainsaw is not getting enough fuel, it can cause the engine to stall. As well as making sure the chainsaw has fresh fuel, also check that the fuel filter is not clogged. A blocked fuel filter can starve your chainsaw’s engine and may also cause harm by allowing tainted fuel to enter the engine.

Carburetor clogs can also be caused by contaminated gasoline. Clogged carburetors are one of the most common causes of a chainsaw not starting or staying running.

Also, check the fuel line for any cracks or leaks. If you find any, replace the fuel line.

Most chainsaw experts advise against using ethanol gas, which is damaging to fuel lines.


Dirty or Clogged Air Filter

Another common cause of a chainsaw that won’t stay running is a dirty air filter. The air filter is responsible for keeping debris and dust out of the engine, and if it’s clogged, it can restrict airflow and cause the chainsaw to stall. To fix this, simply remove the air filter and clean it with a soft brush or compressed air. If the air filter is damaged, replace it with a new one, and then test your chainsaw.

Clogged Fuel Tank Vent

Check the air vent if the fuel tank vent or fuel cap is clogged. To allow free flow of gasoline to the carburetor, the pressure within the fuel tank must equal the atmospheric air pressure. For this reason, most chainsaw fuel tanks feature air vents; just a few chainsaw models have vented gasoline caps.

Check the user manual for your chainsaw to find out where the vent is and how to clean it. If your chainsaw has a vented fuel cap, the job is significantly simpler: clean or replace it. You may do a simple test by loosening the chainsaw’s fuel cap and allowing air into the tank. Now cautiously start your chainsaw. If it continues to run, the problem is the fuel tank venting.

Clogged Exhaust

Check the spark arrester if the exhaust is clogged. Chainsaws are equipped with a spark arrester, which is a tiny screen that prevents sparks from exiting the machine. It’s a fire-prevention feature, especially when working with combustible materials like wood and sawdust. It is important, especially given the strain and speed of aggressive chainsaw chains.


Exhaust gasses must be allowed to exit the engine freely or the engine may stall. Check the spark arrester on your chainsaw to see if it is blocked or broken. If it’s clogged, you can clean it using a wire brush, but if it’s too dirty or broken, you should replace it.

Fix A Chainsaw That Does Not Run

Blocked or damaged Idle Port

Idle Port Blocked or Damaged: Inspect the idle port. The idle port, often known as the idle screw, is used to regulate airflow into the chainsaw engine. Oil, grime, and debris can clog them and prevent air from entering the engine. If your chainsaw’s idle port becomes clogged or broken, it will no longer run. Examine the idle port for damage or obstruction.

If it’s clogged, clean it with alcohol, kerosene, or another solvent. If it is damaged, you must replace it.

Spark Plug

Check your chainsaw’s spark plug for damage. The spark plug is responsible for providing the spark that ignites the fuel in the engine. A faulty spark plug might prevent your chainsaw from starting, causing the engine to lose power and shut down. While your engine is idle or cutting softwood, this power reduction may be imperceptible. However, if your chainsaw’s engine shuts down when cutting tougher wood, this might be the cause.


If the spark plug is dirty or worn out, it can cause the chainsaw to stall. Remove the spark plug and check for any damage or debris. If the spark plug is dirty, clean it with a wire brush and re-install it. If the spark plug is worn out, replace it with a new one.

Clogged or Broken Primer Bulb

Primer Bulb Clogged or Broken? Check the primer bulb. A priming bulb can be found on some chainsaws. If your chainsaw has one, the priming bulb might become clogged with gasoline and/or oil. Its substance can break when exposed to the elements. The flaws enable air to escape, preventing the engine from running properly. If this is the case, replace the priming bulb.

More Technical Reasons Why a Chainsaw Won’t Stay Running

The issues stated thus far should be solvable without the assistance of a professional. We’ll go through more sophisticated situations that demand more technical knowledge and experience down below.

Carburetor Calibration

Adjust the idle, high, and low screws on your chainsaw’s carburetor. The carburetor may need to be adjusted when the engine and its components wear out. Chainsaws are equipped with three adjustment screws that are utilized to provide adequate airflow to the engine. It is difficult to adjust the carburetor on your chainsaw. Every model has unique settings, and tuning an engine by ear is difficult for the inexperienced.


An engine stalls when it does not get enough or too much gasoline from the carburetor. Chainsaws contain a screw that allows you to regulate the airflow while the engine is idle, operating at low speed, or running at high speed.

If the chainsaw stalls while being revved up or if it does not achieve maximum power, the high-speed screw has to be adjusted. If your chainsaw’s engine stops idling, the idle screw has to be adjusted. If it fails at low speeds, the low-speed screw must be adjusted.

Keep in mind that by turning these screws, you are altering the engine’s air-fuel ratio. It is quite dangerous to your engine if you keep the gasoline mixture too thin or too rich. As a result, it is suggested that you take your chainsaw to a service shop for this issue.

Carburetor Clogged

A dirty or clogged carburetor can also cause a chainsaw that won’t stay running. Carburetor clogs can cause an engine to stall or fail to start at all. You might try cleaning it with a carburetor cleaner. If this fails, you can remove it for a more thorough cleaning. You may clean the carburetor with an automotive carburetor cleaner. The carburetor is responsible for mixing the air and fuel before it enters the engine. If the carburetor is clogged, it can restrict the fuel flow and cause the chainsaw to stall. If the carburetor is damaged, replace it with a new one.


Compression Problem

Perhaps your chainsaw is old, has lubrication issues, is difficult to start, or you’ve observed that it didn’t feel as powerful as normal prior to this problem. If this is the case, you should do a compression test.

A healthy engine should have more than 70 PSI for a small saw and at least 100 PSI for larger engine saws. There are low-cost compression tester gauges available on the market. You may perform it yourself or take your chainsaw to a professional shop for testing.

Low compression in your chainsaw’s engine indicates internal issues such as worn piston rings, faulty crankshaft seals, or a broken piston. Repairing these damages is costly, and they may indicate that it is time to purchase a new chainsaw. That is why it is preferable to do a compression test before investing in rather expensive items such as a new carburetor.


The clutch is responsible for connecting the chain to the crankshaft. If the clutch is damaged or worn out, it can cause the chainsaw to stall. To check the clutch, remove the clutch cover and inspect it for any damage or wear. If the clutch is damaged, replace it with a new one.


Chainsaw That Won’t Stay Running FAQ

Chainsaw That Won’t Stay Running Questions and Answers

Why does my chainsaw run for a few seconds then stop?

It’s possible that the carburetor is clogged. A blocked carburetor is frequently the result of leaving gasoline in the chainsaw for an extended length of time. Some of the components in the gasoline may evaporate with time, leaving a thicker, stickier residue. This sticky gasoline might block the carburetor and halt the chainsaw engine.

Why does my chainsaw start then stop?

If the chainsaw won’t start or begins and then stops, and the spark plug is moist with gasoline mixture, the engine is flooded (you will probably smell petrol). It occurs when too much fuel enters the combustion chamber, sometimes as a result of repeatedly pressing the primer.

Why does my chainsaw stall out when idling?

If the engine dies while idling, tighten the idle setting. If the engine does not stall until the throttle is depressed, tighten either the low-speed or high-speed adjustment screw to increase performance.

Why does my chainsaw stop when I give it gas?

If the filter becomes clogged, not enough fuel will reach the engine for it to run properly. Because your chainsaw will idle, but dies when it is revved up to full power, it means that the filter is only partially clogged; it will allow enough fuel to the engine to run on idle, but not enough to sustain full throttle.

How can you tell if carburetor too lean or too rich?

If the carburetor delivers an air/fuel combination that is too lean, the engine will operate sluggishly, overheat, or cause engine damage. If the carburetor is delivering an overly rich air/fuel mixture, the engine may tend to load up, clog the spark plug, operate sluggishly, and lack power.

Where do you spray carburetor cleaner on a chainsaw?

Put some carb cleaner in the pilot air jet of your chainsaw to properly clean the carburetor. The intake mouth is served by this carburetor component.

In conclusion, a chainsaw that won’t stay running can be a frustrating and time-consuming problem, but it’s often an easy fix. By following the simple and easy steps outlined above, you can quickly and easily fix a chainsaw that won’t stay running and get back to work in no time. Remember to always use proper safety precautions when working on a chainsaw, and if you’re unsure about how to fix a problem, consult the manufacturer’s instructions or contact a professional for help.

Always read the user manual for your chainsaw. Free operator manuals, parts list and workshop manuals are available from this website. They contain important information on the parts that must be serviced on a regular basis, as well as other instructions for the machine’s maintenance and your safety.

If you have more chainsaw questions, here at the Chainsaw Workshop Manual website, we are always happy to help!

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