13 Reasons a Chainsaw Starts Then Dies: SOLVED

A chainsaw starts and dies when it isn’t getting sufficient air, fuel, and spark for combustion.

This may be due to a plugged air filter, dirty carburetor, plugged fuel filter, wrong choke setting, bad fuel tank vent, plugged spark arrestor, faulty ignition coil, or plugged cooling system.

Keep reading for additional reasons a chainsaw will quit running. Never perform repairs on a chainsaw without removing the spark plug wire. Wait for the engine and muffler to cool and allow all parts to stop moving.

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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.

This is Why Your Chainsaw Starts Then Dies

1. Wrong Choke Setting

To start a cold engine, the choke must be used to restrict air so the fuel mixture runs rich. This allows a higher concentration of fuel and less air to be pulled into the engine to start it.

Once the engine is warm, the choke must be off to correct the fuel-to-air mixture so it no longer runs rich and allows the engine to keep running.

When the choke isn’t in the off/open position, the engine may begin to run sluggishly and die because it isn’t getting sufficient air.

2. Dirty Air Filter

The air filter is a maintenance part used on a chainsaw to keep dirt from entering the carburetor throat and causing engine wear. This filter must be kept clean and in good condition.

It’s best to replace the air filter annually for the average homeowner and inspect it frequently throughout the year to clean or replace it if necessary.

When filter maintenance is skipped, the filter can become plugged with dirt, sawdust, and debris. The buildup can be significant enough to reduce airflow through the filter. When this happens, the chainsaw will stall and die.

3. Plugged Cooling System

The cooling system must be kept clean to keep the engine from getting too hot, overheating, and shutting down. To help cool the engine, remove dirt and debris that block the air intake and cooling fins.

To do this, first, remove the spark plug and wait for the engine to cool. Remove the engine cover and remove debris from the cover and around the outside of the cylinder.

Clean the cylinder cooling fins, the pawls on the flywheel, and other areas air moves through the chainsaw. Reinstall the engine cover. Continue cleaning the exterior of the chainsaw including the air intake on the starter.

4. Plugged Spark Arrestor

A spark arrestor screen is attached to the muffler to keep hot exhaust material from shooting out of the muffler.

This screen must be cleaned out regularly or the buildup of carbon can keep the exhaust air from exiting the muffler causing it to shut down.

To clean the spark arrestor, begin by removing the spark plug wire and allowing the muffler to cool. Then remove the spark arrestor screen on the muffler

Clean the screen with a metal brush. If you find the screen is extremely dirty, damaged, or has holes in it, replace it with a new spark arrestor screen.

To minimize carbon building up on the spark arrestor quickly, make sure you periodically run your chainsaw at full throttle. Letting your chainsaw idle or run at low speeds for a long time will contribute to a buildup of carbon.

5. Old Fuel

Fuel can be the biggest culprit when it comes to a chainsaw not running well and dying. Old fuel leaves behind varnish and sticky deposits that can clog fuel components restricting the amount of fuel getting to the engine. This can cause the saw to shut off.

To reduce the negative effects of fuel on your chainsaw always use a gas with no greater than a 10% ethanol content.

Here are a few tips for selecting and caring for fuel:

• Only use fresh fuel. Fuel can begin to degrade as quickly as 30 days after purchase.
• Use the right fuel. 2-cycle and 4-cycle chainsaws have different fuel requirements. Using the wrong fuel can cause it to die.
  • 2-cycle engine: Most common chainsaws require a 50:1 gas-to-oil mixture. You may find others require a 40:1 mixture. Read more about fuel to use in your chainsaw here.
    • Select gasoline with a minimum octane rating of 89 and a maximum ethanol content of 10%.
    • Mix in a premium 2-cycle oil that is ISO-L-EGD and JASO M345 FD certified.
  • 4-cycle engine: Do not mix oil with gas in these types of engines. There are separate fuel ports for gas and oil.
    • Select gasoline with a minimum octane rating of 89 and a maximum ethanol content of 10%.
• Add a fuel stabilizer. To prevent gas from breaking down so it lasts a little longer, add a fuel stabilizer like Sea Foam or STA-BIL. These products will reduce moisture and clean the fuel system as well.

6. Plugged Fuel Filter

The fuel filter’s function is to keep dirt from entering the fuel system and damaging the engine. The fuel filter is a small cylinder-shaped part located inside the fuel tank.

You will find it attached to the fuel line. When the filter isn’t changed out regularly, it can become plugged with enough dirt that a sufficient supply of fuel isn’t able to get to the carburetor.

Inspect the filter and replace it if needed. I like to replace it annually and more often if I begin using it regularly.

I use my saw a lot during the winter and not too much the rest of the year. I typically change the fuel filter before and after the winter season.

Change a chainsaw fuel filter:

• First, wipe around the fuel tank cap so dirt doesn’t fall into the tank.
• Pull the filter out of the tank using a filter hook or a clean bent wire.
• Once the filter is out of the tank, grab the fuel line with one hand and pull the filter out of the line with the other hand.
• Insert a new fuel filter into the line.
• Place the fuel filter inside the tank.
• Reinstall the fuel cap.

7. Clogged or Punctured Fuel Line

Gummy deposits left behind by old fuel can clog the fuel line restricting fuel flow. When you find a clogged fuel line, remove it from the chainsaw and clean it to open the line.

Spray carburetor cleaner into the line to loosen the clog. Follow this with compressed air to dislodge and remove the clog. Repeat as necessary to remove the clog.

If you can’t remove the clog or you find the fuel line is dry and cracked, you need to replace the fuel line with a new line of the same diameter and length.

Also, replace any line that has a puncture. A punctured fuel line can draw air into the fuel system resulting in a chainsaw running sluggish because too much air is being introduced to the cylinder.

8. Plugged Fuel Tank Vent

A chainsaw’s fuel tank must be able to vent allowing air to flow into the tank as fuel is consumed. Without a vent, a vacuum forms keeping fuel from getting to the carburetor.

Locate the fuel vent on your chainsaw and replace a clogged vent. On most chainsaws, it is typically a small circular part that is installed on the top side of the fuel tank.

9. Dirty Carburetor

The carburetor mixes the correct proportion of air and fuel required for your chainsaw to start and continue to run. The passageways can become clogged and the small components can fail to function correctly which can be the reason the chainsaw stops running.

Old fuel is often the main reason a carburetor stops working. You may be able to clean or rebuild your carburetor to get it working again. You will have to replace the carburetor if this doesn’t work.

10. Carburetor Needs Adjustment

The carburetor may need to be adjusted to change the RPMs at idle speed and at full throttle. There are adjustment screws on the carburetor to make these adjustments.

You will find a low-speed and high-speed screws. To adjust the carburetor on many chainsaw models, let the chainsaw idle and adjust the low-speed screw clockwise and counter-clockwise until you find the “sweet spot” where it runs smoothly and not sluggish.

Next, adjust the high-speed screw to get a good smooth RPM at full throttle. Don’t over-adjust and allow the RPMs to increase too much or you will damage the engine.

Many chainsaw manufacturers place limits on the adjustments you can perform to the carburetor.

If you are continuing to have problems with the carburetor or your chainsaw doesn’t allow you to make carburetor adjustments, bring your chainsaw to your local chainsaw dealer.

A special tool may be required so only your dealer can make the necessary adjustments.

11. Bad Spark Plug

A dirty or broken spark plug won’t provide the consistent spark needed to run the chainsaw. It may provide intermittent spark causing the saw to lose power and possibly die.

Inspect the condition of the spark plug tip. If it is very dark in color and has a broken porcelain or burnt electrode, the spark plug must be replaced.

You can try to clean the spark plug with a wire brush and reuse it if it’s just a little dirty. I prefer to just replace it. It’s a necessary part that must be in good condition for your chainsaw to run and perform well.

Make sure the spark plug is gapped correctly and the spark plug wire is securely attached. (Don’t leave the spark plug attached if you need to continue to make additional repairs).

12. Faulty Ignition Coil

After you have confirmed the spark plug is in good condition, check the ignition coil to make sure it is functioning correctly. The coil provides the electrical current to the spark plug to form a spark that ignites the fuel to start and keep your chainsaw running.

When the coil gets hot, the winding on the coil can separate and short out. This will cause your chainsaw to lose power, run sluggishly or stop running when there is an intermittent spark.

A bad ignition coil will not be able to provide sufficient voltage to the spark plug.

13. Compression Problem with a Chainsaw Engine

While pulling the starter recoil rope, you may notice a loss of compression. When the compression is low on a chainsaw, it will fail to have enough pressure to keep it running.

This can be the result of worn crankshaft seals, worn piston rings, or damage to the piston.

I advise bringing your chainsaw to a small engine mechanic or your local chainsaw dealership for testing and making necessary repairs.