Any tool that requires an engine to power will eventually run into issues with the various components within. And when it comes to your Stihl chainsaw, there are plenty of reasons why it may sputter or fail to start entirely.
So, what do you do when the chainsaw won’t start as it should? It could come down to the fuel intake, issues with the ignition spark, carburetor issues, compression-related problems, and more. It is important to troubleshoot the issue to determine the cause and then correct the problem in short order.
A Little About the Stihl Chainsaw Engine
The great thing about Stihl chainsaws is that they come with a two-stroke engine. What is that? Well, the two-stroke engine is designed and built to limit the number of parts within that can ultimately lead to engine failure.
That’s not to say that engine failure is no longer possible. There are still some common components to this engine that are similar to most combustion engines out there. Finding the source of the problem is important for understanding what the issue may be.
Problems with the Fuel Intake
Your Stihl chainsaw requires the proper level of fuel inside of the cylinder at just the right time. When you start the engine, the crankshaft will spin, and a vacuum pressure will be created on the carburetor; this is what sucks the fuel up from the gas tank.
That fuel is then mixed together with air within the carburetor before it is ultimately sent to the cylinder. When there is a restriction in the flow of air or fuel, the mix will be off and there will be no ignition in the cylinder.
Restrictions of Fuel Flow
Clogged or dirty fuel filters, fuel tanks, and fuel lines, dirty air filters, loose fuel hoses, or a dirty carburetor can all be responsible for the restriction of that fuel flow. Make sure that you not only check each of these components but clean them appropriately or replace any fuel system components that may be damaged.
Gas, whether it be a lack of it or some that have been left to sit in the fuel tank for too long, create the vast majority of problems when it comes to the engine turning over and starting. Whenever your Stihl chainsaw won’t start, the fuel system is the first place to start.
Problems with Ignition Spark
In the Stihl chainsaw, the crankshaft powers the flywheel. The flywheel, when it spins, there are a pair of magnets that ultimately generate magnetic energy. After enough of that magnetic energy has been created, it will trip the ignition module.
When the ignition module has been tripped, this is what sends the spark up to the plug, thereby igniting the fuel. When there is a problem within the ignition system, it will keep the engine from firing up properly.
Corroded and Damaged Wiring
Spark plugs that are corroded or bad, broken wires, faulty wiring connections, and a faulty ignition module could all be the cause. It could even come down to an improper air gap between the ignition module and the flywheel. All of these will keep the engine from combusting and, ultimately, starting.
Start by checking out the spark plug. When it comes to the ignition system, the spark plug is the issue 9 times out of 10. If it isn’t the spark plug, work towards the flywheel and ignition module, checking the various points of the mower’s ignition system.
Check the Carburetor
The carburetor is what brings the fuel out of the tank, mixes it with some air, and then moves it into the cylinder of the engine. Most combustion engines of this sort are regulated through a trio of chambers. The first is the metering section; this is where the fuel gets measured. The second is the mixing section. And finally, there is the fuel pump.
When there are issues with the carburetor, the fuel won’t arrive in the cylinder, at least not in the right volume and definitely not at the right time. Dirty jets or bores, stuck levers, improperly seated needle valves, and warped or ripped diaphragms can all stop the fuel from moving through the carburetor.
1. Take apart the carburetor. When the carburetor is the clear problem, take it apart completely.
2. Clean the components. After removal, clean each of the components. Should any of the components be worn, it is best to install a carburetor upgrade kit.
3. Install an upgrade kit. This will save you some time and money as opposed to replacing the carburetor entirely.
4. Replace the carburetor. If that still doesn’t solve the problem, replace the entire carburetor.
Problems with Compression
The Stihl chainsaw requires compression to make the fuel system and spark system work cohesively together. When the piston moves up and down within the cylinder, it ultimately generates compression.
Compression within your chainsaw’s engine can become compromised due to a leak coming from somewhere inside of the engine. It can also emanate from a potential clog in the air or fuel system as well.
What Happens When Compression is Bad?
If the compression isn’t regulated properly, it can cause the piston to seize up within the cylinder. This is what can end your engine’s life. The bad thing is that most compression issues will require the help of a professional mechanic.
Start by troubleshooting the aforementioned issues, eventually working towards compression. Don’t take on compression repairs yourself as it ties into both the fuel and spark systems.
Other Individual Components
Though 9 out of 10 starting issues will emanate from one of the aforementioned systems, it doesn’t mean that those are the only potential issues. There are plenty of other components within your chainsaw’s engine that can go wrong from time to time.
Always start your troubleshooting efforts by checking out the fuel or spark system and working your way to the more difficult components.
This is part of the spark system but most of those issues revolve around the spark plug. The ignition coil is responsible for sending the appropriate amount of voltage into the spark plug as the engine runs. When the coil can’t do its job, the engine can’t run effectively if at all.
1. Check the spark plug. Always start out by checking the spark plug to ensure that it is working optimally.
2. Check the ignition coil. You can continue to check the spark system by then moving on to the ignition coil. Use an ignition coil tester to check the continuity of the ignition coil. If it is defective or damaged, you will have to replace it.
Check the Recoil Starter
Finally, the issue could come down to the recoil starter assembly. This is the component that will engage the crankshaft, allowing the engine to turn over. When the recoil starter assembly is damaged or defective, the engine won’t be able to turn over properly and your chainsaw will not start.
1. Take out the starter assembly. After troubleshooting all of the prior potential causes, take out the starter assembly entirely and give it a thorough inspection.
2. Look for damage. Look for potential damage or excessive wear and tear that could prevent the assembly from working optimally.
3. Release the rope. Normally, when you pull the starter rope, there are tabs that will extend out from the cam and pulley, which grab onto the hub that is on the engine itself. This system comes together to turn the engine over. When you release that rope, the tabs will retract, rewinding the rope back onto the pulley. If this is damaged or broken, you will need to replace it.
What is the Choke on a Chainsaw?
You may notice on your Stihl chainsaw that there is something called a choke. The purpose of the choke is to potentially make the process of cold starting easier, but it has to be used properly in order to work effectively.
When you make use of the choke, the carburetor then sprays a little bit of extra fuel into the combustion chamber after the starter is pulled.
What is Flooding?
Should the engine not start after, at most, three to four pulls, the air and fuel mixture will become too rich. Continuing to pull the starter with the choke closed will create too much fuel to properly ignite, leading the engine to flood.
Thankfully, there are a couple of ways to fix engine flooding. The first is to simply wait for the fuel to drain out or you can follow the below tips for fixing a flooded engine.
Fixing a Flooded Engine
1. Find a flat surface. Start first by putting the chainsaw down on a flat, level surface. Also, make certain that the chain break on your chainsaw has been activated.
2. Remove the spark plug. Next, pull the wire off of the spark plug and remove the component entirely using the designated spark plug wrench.
3. Clean and check. Check all of the electrodes on and around the spark plug, wiping them off using a clean, dry rage if they are covered in dirt, fuel, or both.
4. Check the air filter. You will also want to take the air filter cover off, removing the air filter as well. Treat the air filter as you would the spark plug: inspect it and clean it if it is dirty.
5. Set choke position. Finally, set the master control lever to the open or minimum choke position. Pull on the starter rope five to six times; this will clear the fuel out of the chamber. Put everything back together, leaving the choke open. After a few pulls, the chainsaw should start.