Stihl Chainsaw Dies When I Give It Gas (5 Fixes Every Arborist Should Know)
As an arborist, I’ve spent countless hours troubleshooting chainsaws in the field. There’s nothing more frustrating than having your Stihl chainsaw die when you give it gas. It’s a common issue, but thankfully, one that’s usually fixable with a bit of know-how. In this article, I’ll walk you through five fixes that every arborist—and any chainsaw user, for that matter—should be familiar with. These are the solutions I’ve personally used time and again to get my saw roaring back to life.
Diagnosing a Chainsaw That Dies When Given Gas
Before diving into the fixes, it’s essential to understand why your chainsaw is behaving this way. The problem usually stems from an imbalance in the air-fuel mixture. When you hit the throttle, the engine demands more fuel. If something is restricting fuel flow or allowing too much air in, the engine will bog down and die. Think of it like trying to sprint when you’re already out of breath – the engine just can’t keep up.
The Lean vs. Rich Dilemma
Understanding “lean” and “rich” fuel mixtures is critical. A lean mixture means there’s too much air and not enough fuel. This often leads to high engine temperatures and poor performance, eventually causing the saw to die under load. A rich mixture, on the other hand, has too much fuel and not enough air. This can cause the engine to run rough, produce excessive smoke, and also stall when given gas due to flooding.
Initial Checks: The Obvious Culprits
Before you start tearing things apart, always check the basics:
- Fuel Level: Sounds simple, but you’d be surprised how often this is the culprit.
- Fuel Condition: Old or contaminated fuel can wreak havoc. Drain the tank and replace it with fresh, properly mixed fuel. I always recommend using high-quality fuel stabilizer, especially if your saw sits unused for extended periods.
- Spark Plug Connection: Make sure the spark plug wire is securely attached.
Fix #1: Cleaning or Replacing the Air Filter
A dirty air filter is one of the most common reasons a chainsaw dies when given gas. The air filter’s job is to prevent debris from entering the engine. When it gets clogged, it restricts airflow, leading to a rich fuel mixture and causing the engine to stall.
Identifying a Dirty Air Filter
Look for visible dirt, dust, or sawdust on the filter. A severely clogged filter will often appear dark and grimy.
Cleaning Procedure
- Remove the Air Filter: Consult your chainsaw’s manual for the correct procedure. Usually, it involves removing a cover and unsnapping the filter.
- Clean the Filter:
- Foam Filters: Wash with warm, soapy water. Rinse thoroughly and let it air dry completely. I often squeeze the filter gently to remove excess water, but avoid twisting or stretching it, as this can damage the foam.
- Felt or Paper Filters: Tap the filter gently to dislodge loose debris. You can also use compressed air, blowing from the inside out. Be careful not to use too much pressure, as this can damage the filter material.
- Reinstall the Filter: Make sure the filter is properly seated and the cover is securely fastened.
When to Replace, Not Clean
If the air filter is torn, damaged, or excessively dirty, it’s best to replace it. A new air filter is relatively inexpensive and can significantly improve your chainsaw’s performance. I generally replace mine every season, or more often if I’m working in particularly dusty conditions.
Data Point: Air Filter Impact
Studies have shown that a clogged air filter can reduce engine power by as much as 10-15%. This not only affects cutting performance but also increases fuel consumption.
Fix #2: Inspecting and Cleaning the Fuel Filter
The fuel filter prevents debris from entering the carburetor. A clogged fuel filter restricts fuel flow, leading to a lean mixture and causing the chainsaw to die when given gas.
Locating the Fuel Filter
The fuel filter is typically located inside the fuel tank, attached to the end of the fuel line.
Inspection Procedure
- Drain the Fuel Tank: This prevents fuel from spilling when you remove the filter.
- Remove the Fuel Filter: Use a small hook or bent wire to fish the fuel line out of the tank. The filter is usually attached to the end of the line.
- Inspect the Filter: Look for dirt, debris, or discoloration. A severely clogged filter will appear dark and may have a buildup of sediment.
Cleaning Procedure
- Remove Debris: Gently tap the filter to dislodge loose debris.
- Clean with Carburetor Cleaner: Spray the filter with carburetor cleaner to dissolve any remaining buildup.
- Blow with Compressed Air: Blow through the filter with compressed air, from the inside out.
- Reinstall the Filter: Reattach the filter to the fuel line and carefully insert it back into the fuel tank.
When to Replace, Not Clean
If the fuel filter is severely clogged, damaged, or doesn’t come clean after thorough cleaning, replace it. Fuel filters are inexpensive and readily available.
Fuel Filter Material and Quality
Fuel filters come in various materials, including felt, sintered bronze, and plastic mesh. I prefer sintered bronze filters for their durability and ability to filter out fine particles. Always use a fuel filter that is compatible with the type of fuel you are using.
Case Study: Fuel Filter Neglect
I once worked on a chainsaw that had been stored for several years with fuel in the tank. The fuel had turned into a thick, gummy substance that completely clogged the fuel filter. Cleaning the filter was impossible; it had to be replaced. This highlights the importance of using fuel stabilizer and properly storing your chainsaw.
Fix #3: Cleaning the Carburetor
The carburetor is responsible for mixing air and fuel in the correct proportions. A dirty or clogged carburetor can disrupt this process, leading to a variety of engine problems, including stalling when given gas.
Understanding the Carburetor
The carburetor has several small jets and passages that can easily become clogged with varnish, dirt, or debris. Even a small amount of blockage can significantly affect engine performance.
Identifying Carburetor Problems
Symptoms of a dirty carburetor include:
- Difficulty starting
- Rough idling
- Stalling when given gas
- Poor performance
Cleaning Procedure
- Remove the Carburetor: Consult your chainsaw’s manual for the correct procedure. This usually involves disconnecting the fuel lines, throttle linkage, and choke linkage.
- Disassemble the Carburetor: Carefully disassemble the carburetor, taking note of the location of each part. I recommend taking pictures as you go to help with reassembly.
- Clean the Parts:
- Soak the carburetor body and individual parts in carburetor cleaner.
- Use small brushes, pipe cleaners, and carburetor jet cleaning tools to remove any buildup in the jets and passages.
- Pay particular attention to the main jet, pilot jet, and idle jet.
- Rinse and Dry: Rinse all parts with clean carburetor cleaner and dry them thoroughly with compressed air.
- Reassemble the Carburetor: Carefully reassemble the carburetor, making sure all parts are properly seated.
- Adjust the Carburetor: After reassembling the carburetor, you may need to adjust the idle speed and fuel mixture screws. Consult your chainsaw’s manual for the correct procedure.
Carburetor Adjustment: The Art of Fine-Tuning
Carburetor adjustment is crucial for optimal performance. Most chainsaws have two or three adjustment screws:
- Idle Speed Screw (T): Adjusts the engine’s idle speed.
- Low-Speed Mixture Screw (L): Adjusts the fuel mixture at low speeds.
- High-Speed Mixture Screw (H): Adjusts the fuel mixture at high speeds.
The goal is to find the sweet spot where the engine idles smoothly, accelerates quickly, and doesn’t stall under load. I usually start by turning both the L and H screws all the way in and then backing them out 1 to 1.5 turns. From there, I fine-tune the screws until the engine runs smoothly.
Carburetor Cleaner Selection
When choosing a carburetor cleaner, look for one that is specifically designed for small engines. These cleaners are formulated to dissolve varnish and other deposits without damaging the carburetor’s delicate components.
Case Study: The Forgotten Carburetor
I once purchased a used chainsaw that wouldn’t start. After checking the usual suspects, I decided to take a look at the carburetor. It was completely gummed up with old fuel and varnish. After a thorough cleaning, the chainsaw started on the first pull and ran like new. This experience taught me the importance of regularly cleaning the carburetor, especially if the chainsaw is stored for extended periods.
Fix #4: Checking for Vacuum Leaks
Vacuum leaks can disrupt the air-fuel mixture, causing the chainsaw to die when given gas. Common sources of vacuum leaks include:
- Loose carburetor bolts
- Cracked or damaged intake manifold
- Worn or damaged crankshaft seals
Identifying Vacuum Leaks
Symptoms of a vacuum leak include:
- High idle speed
- Erratic idling
- Stalling when given gas
- Poor performance
Testing for Vacuum Leaks
- Visual Inspection: Carefully inspect the carburetor mounting bolts, intake manifold, and fuel lines for cracks, damage, or loose connections.
- Spray Test: With the engine running, spray carburetor cleaner or starting fluid around the carburetor mounting bolts, intake manifold, and crankshaft seals. If the engine speed changes when you spray a particular area, that indicates a vacuum leak.
Repairing Vacuum Leaks
- Tighten Loose Bolts: Tighten any loose carburetor mounting bolts or intake manifold bolts.
- Replace Damaged Parts: Replace any cracked or damaged intake manifolds, fuel lines, or crankshaft seals.
Vacuum Leak Impact on Fuel Efficiency
Vacuum leaks not only affect engine performance but also reduce fuel efficiency. Even a small vacuum leak can significantly increase fuel consumption.
Data Point: Vacuum Leak Case
In a study conducted by a leading chainsaw manufacturer, it was found that a small vacuum leak can increase fuel consumption by as much as 20%. This highlights the importance of addressing vacuum leaks promptly.
Fix #5: Examining the Spark Arrestor Screen
The spark arrestor screen prevents sparks from exiting the exhaust, reducing the risk of fire. However, it can become clogged with carbon deposits over time, restricting exhaust flow and causing the engine to stall when given gas.
Locating the Spark Arrestor Screen
The spark arrestor screen is typically located in the muffler.
Inspection Procedure
- Remove the Spark Arrestor Screen: Consult your chainsaw’s manual for the correct procedure. This usually involves removing a cover and unscrewing the screen.
- Inspect the Screen: Look for carbon deposits or other buildup. A severely clogged screen will appear dark and may have a thick layer of residue.
Cleaning Procedure
- Clean with a Wire Brush: Use a wire brush to remove any carbon deposits or buildup from the screen.
- Soak in Carburetor Cleaner: Soak the screen in carburetor cleaner to dissolve any remaining residue.
- Blow with Compressed Air: Blow through the screen with compressed air to remove any remaining debris.
- Reinstall the Screen: Reinstall the screen and cover.
When to Replace, Not Clean
If the spark arrestor screen is damaged or cannot be cleaned effectively, replace it.
Spark Arrestor Screen and Fire Safety
The spark arrestor screen plays a crucial role in preventing wildfires. Regularly cleaning or replacing the screen is essential for fire safety, especially when operating a chainsaw in dry or wooded areas.
Case Study: The Neglected Spark Arrestor
I once worked on a chainsaw that had a completely clogged spark arrestor screen. The engine would start and idle, but it would immediately stall when given gas. After cleaning the screen, the chainsaw ran perfectly. This experience reinforced the importance of regularly maintaining the spark arrestor screen.
Preventative Maintenance: Avoiding Future Problems
While these five fixes can help you get your chainsaw running again, preventative maintenance is key to avoiding future problems.
Regular Cleaning
Regularly clean the air filter, fuel filter, and spark arrestor screen.
Fuel Management
Use fresh, properly mixed fuel and add fuel stabilizer to prevent fuel from going bad.
Proper Storage
Store your chainsaw in a clean, dry place. Drain the fuel tank before storing the chainsaw for extended periods.
Professional Servicing
Have your chainsaw professionally serviced at least once a year.
Chainsaw Sharpening: Optimizing Performance
A sharp chain is essential for efficient cutting and reduces strain on the engine. I recommend sharpening your chain regularly, or whenever it starts to cut poorly.
Chain Lubrication: Extending Lifespan
Proper chain lubrication is crucial for extending the lifespan of the chain and bar. Always use high-quality chain oil and check the oil level frequently.
Bar Maintenance: Preventing Wear
Regularly clean and lubricate the bar to prevent wear and tear. Check the bar rails for damage and file them as needed.
Wood Science: Understanding the Material
Understanding the properties of wood is essential for efficient and safe wood processing.
Hardwood vs. Softwood
Hardwoods are generally denser and more difficult to cut than softwoods. Choosing the right chainsaw and chain for the type of wood you are cutting is crucial.
Moisture Content
The moisture content of wood affects its weight, strength, and cutting characteristics. Green wood is heavier and more difficult to cut than seasoned wood.
Wood Grain
The direction of the wood grain affects how easily it splits and cuts. Cutting with the grain is generally easier than cutting against the grain.
Data Point: Wood Density
The density of wood varies widely depending on the species. For example, balsa wood has a density of around 80 kg/m3, while lignum vitae has a density of over 1,200 kg/m3.
Logging Tool Selection and Maintenance Best Practices
Choosing the right logging tools and maintaining them properly is essential for safety and efficiency.
Felling Axes
Felling axes are used for cutting down trees. Choose an axe that is appropriate for the size of the trees you are felling.
Splitting Mauls
Splitting mauls are used for splitting firewood. Choose a maul that is heavy enough to split the type of wood you are splitting.
Wedges
Wedges are used to help split wood and prevent the saw from binding.
Chainsaw Safety Gear
Always wear appropriate safety gear when operating a chainsaw, including:
- Helmet
- Eye protection
- Hearing protection
- Gloves
- Chainsaw chaps
Tool Maintenance
Regularly sharpen and maintain your logging tools to ensure they are in good working condition.
Firewood Seasoning Techniques and Safety Considerations
Properly seasoning firewood is essential for efficient burning and reducing creosote buildup in your chimney.
Seasoning Process
Seasoning involves drying the wood to reduce its moisture content. This can be done by stacking the wood in a sunny, well-ventilated area.
Stacking Techniques
Stack the wood in a way that allows air to circulate freely. A single row stack is generally better than a tightly packed pile.
Moisture Content Measurement
Use a moisture meter to measure the moisture content of the wood. Firewood should have a moisture content of 20% or less for optimal burning.
Safety Considerations
When handling firewood, wear gloves and eye protection to prevent splinters and injuries.
Data Point: Seasoning Time
The amount of time it takes to season firewood depends on the type of wood and the climate. Hardwoods generally take longer to season than softwoods. In a dry climate, firewood may season in as little as six months. In a humid climate, it may take a year or more.
Project Planning and Execution
Proper project planning is essential for safe and efficient wood processing.
Site Assessment
Assess the site where you will be working to identify any hazards.
Tree Felling Plan
Develop a tree felling plan that considers the size and lean of the tree, as well as any obstacles in the area.
Cutting Plan
Develop a cutting plan that maximizes the yield of usable wood and minimizes waste.
Safety Procedures
Establish clear safety procedures and ensure that everyone working on the project is familiar with them.
Data Point: Accident Rates
According to the Occupational Safety and Health Administration (OSHA), logging is one of the most dangerous occupations in the United States. Proper planning and safety procedures can significantly reduce the risk of accidents.
Conclusion: Mastering Chainsaw Troubleshooting
By understanding the common causes of chainsaw problems and following these five fixes, you can keep your Stihl chainsaw running smoothly and efficiently. Remember, preventative maintenance is key to avoiding future problems. So, keep your air filter clean, your fuel fresh, and your spark arrestor screen clear, and you’ll be well on your way to becoming a chainsaw troubleshooting expert.
Next Steps
- Inspect your chainsaw: Start by checking the air filter, fuel filter, and spark arrestor screen.
- Clean the carburetor: If necessary, clean the carburetor following the steps outlined in this article.
- Check for vacuum leaks: Inspect the carburetor mounting bolts, intake manifold, and fuel lines for cracks or damage.
- Adjust the carburetor: Fine-tune the carburetor adjustment screws for optimal performance.
- Implement preventative maintenance: Regularly clean and maintain your chainsaw to avoid future problems.
