Stihl Chainsaw Won't Stay Running

If your Stihl chainsaw won't stay running it not only wastes valuable time, but it's also extremely aggravating.

As you head into the woods for a full day of cutting firewood, there is no single thing that is more annoying than a chainsaw that starts - and then keeps shutting off.

Want to shed some light on why your saw refuses to stay running?

This article will teach you how to fix some of the most common problems with your chainsaw so you don’t have to deal with this issue in the future.

Why Does My Chainsaw Keep Shutting Off?

Below, we will take a look at some of the most common problems that cause chainsaws to shut off - and then we’ll address how to fix them so you can get your saw up and running.

Old Gas or Bad Fuel

First on your list should be the gas.

Is it old?

Has it gone bad?

With so much ethanol being used in gas these days, many people are experiencing problems like these, especially if they are allowing their chainsaws to sit idle for long periods of time.

Ethanol, when used as an additive to many grades of gas, will begin to turn into a gel-like substance.

This gums up fuel lines and eventually clogs the carburetor.

Stihl 50:1 High Performance Fuel Mix

Choking the chainsaw may get the saw started, but because of the restriction of gas flow, it will repeatedly shut off as the choke is turned off.

To fix the problem, start by draining the gas tank.

Replace the old gas with a fresh mix of gas, being sure to add a stabilizer to keep the ethanol from gelling.

Often, just getting fresh gas and stabilizer through the chainsaw’s fuel system may correct the saw and it should stay running.

When at the gas pump next time with your chainsaw gas can to be filled, try to buy the very best gas that is offered at that pump.

Choose the highest octane available, as the ethanol reduces as the octane goes up.

Some gas stations even offer ethanol-free gas, often referred to as rec fuel, which is a definite must if you’re planning on filling your chainsaw with it.

What you may save by buying cheaper gas for your saw will almost always cost so much more in repairs and lost productivity - and of course, added frustration.

Clogged or Bad Carburetor - Stihl Chainsaw Won't Stay Running

The next step is to check the carburetor for clogs.

You also want to make certain the carburetor hasn't become defective.

Determining a clogged or bad carburetor is typically evident when your saw develops the following symptoms.

In this situation, gas and air flow are not mixing properly.

This proper mixing is absolutely essential for the saw to run at its highest efficiency.

Here are the most common signs of a clogged or bad carburetor:

• Lack of power
• Engine may sometimes overheat
• Fuel efficiency can be greatly reduced
• Engine starves for gas shutting down soon after starting
• Lack of performance of saw
• Chainsaw becomes sluggish as you try to make a cut
• Smoke may come from the carburetor often with a burnt smell

Let's take a look at correcting this problem.

First, add stabilizer to the gas tank.

With the switch off so the saw will not start, pull the start cord a few times with short pauses in between.

This process will move the stabilizer into the carburetor and often remove residue that has built up internally in the carburetor.

It may be necessary to clean the needle valves on the carburetor.

Often, they can be built up with issues from ethanol fuels.

They can also be filled with debris that may have gotten past the air filter and into the carb.

Remove the air filter so that the intake on the carburetor is now visible.

Clean this entire area of debris.

With the float and needle valves removed, spray carb cleaner into needle valve holes to clean them.

Next, clean the needle valves and replace them.

Issue With Fuel Filter or Fuel Lines

Over time and with many refuelings, debris can get into the gas tank.

It will eventually begin to clog up the filter.

Ethanol in the fuel mix may also gum up the filter if the saw sits for extended periods of time.

With the gas filter in the fuel tank and fuel lines quite visible, the replacement of each is quick and easy.

In most cases, lines and filters are simply a push on type of application.

Clogged Air Filter

Clogged air filters will usually be noticeable before they actually stop the saw from running.

The user will notice a loss of power and loss of acceleration as the filter begins to reach a certain point.

Air filters should be replaced frequently, especially in dusty conditions.

Clogged Exhaust - Stihl Chainsaw Won't Stay Running

A clogged exhaust will often exhibit the same symptoms as an air filter issue.

A clogged exhaust will cause a chainsaw to overheat, which could cause damage to the saw's engine.

Clogged exhaust systems will almost always be due to issues with the screen on the outside of the muffler where exhaust exits the engine.

Debris over time can fill this screen, restricting air flow.

To fix this problem, simply remove the screen and brush it clean.

Carburetor cleaner may be used if necessary to help loosen stuck or burned on material.

Never run a chainsaw without the screen, as this is designed as a spark arrestor to avoid the potential of a thrown spark.

Clogged Fuel Cap or Fuel Tank Vent

Fuel caps are vented on chainsaws to allow vapors to escape the tank, keeping the pressure equal and the same for vents.

When these two parts aren’t functioning, the unequal pressures will prevent the saw from running.

To correct this problem, the fuel cap can be washed in warm water with dish detergent and replaced.

A fuel tank vent is a bit more involved.

Locate the vent line on your saw.

Typically the vent will be on the left of the rear handle and beside the starter cover.

Pry the tank vent off with needle nose pliers.

Pull the tank vent out of its seat and remove it along with the line from the saw.

Next, the grub screw must be removed from the vent line using a 3mm drift or punch.

Push the screw out of the line.

Wash all the pieces in warm water and dish detergent and replace them.

Blocked/Damaged Idle Port

The idle port, or idle screw, as it is more commonly known, is used to direct air flow into the carburetor to keep it running smoothly.

Often, these can become dirty with debris such as oil and dirt, which can block airflow.

The screw or port can be cleaned with alcohol, kerosene, or almost any solvent.

A damaged port will need to be replaced.

Bad Spark Plugs

Spark plugs provide the spark needed not only to start the saw but to keep it running once started.

Spark plugs often build up with carbon deposits on the electrode, preventing the plug from firing.

Sometimes, the porcelain section may become cracked as well due to high temperatures.

In a pinch, cleaning the electrode on the plug may get you by but it is always best just to replace it as needed.

Stihl Chainsaw Won't Stay Running - Other Common Issues

The problems described above are, without a doubt, the most common issues that result in a chainsaw that keeps stalling, or idles really rough.

But if your Stihl chainsaw won’t stay running and those issues aren’t to blame, there could be another culprit.

Other issues you may need to address include:

• A clogged or damaged primer bulb (you will likely need to replace the bulb if it has become cracked or broken)

• Compression problems (both high or low compression can prevent your saw from operating as they should)

• Improper mixing of chainsaw gas

Troubleshooting issues with chainsaws can often be the most difficult piece of the problem.

So hopefully, in our review of why your Stihl chainsaw won't stay running, we have answered at least some of the questions you may have so you can work toward fixing the problem!

About the Author

Nick Greenway

Obsessed with firewood, Nick is behind over 350+ of Firewood For Life's articles, as well as countless reviews, guides and YouTube videos to help readers like you reduce heating costs and create the perfect fire.