Chainsaw Won’t Start with Starting Fluid (5 Expert Fixes)

Craftsmanship isn’t just about the final product; it’s about the journey, the understanding of materials, and the relentless pursuit of perfection. It’s the knowledge passed down through generations, adapted and refined through experience. For me, working with wood, whether it’s felling a tree or splitting firewood, embodies this spirit. It’s a dance between man and nature, where respect for the material is paramount. It’s about understanding the grain of the wood, the tension within, and how to coax it into submission.

I’ve spent years honing my skills, learning from seasoned loggers and experimenting with different techniques. I’ve seen firsthand how a deep understanding of the tools and the wood itself can transform a seemingly impossible task into a rewarding accomplishment. And I’ve learned, often the hard way, that shortcuts and assumptions can lead to frustration, wasted effort, and even danger.

Chainsaw Won’t Start with Starting Fluid (5 Expert Fixes)

When your chainsaw refuses to roar to life despite a shot of starting fluid, it signals a deeper issue than just a simple fuel delivery problem. Starting fluid is essentially a highly volatile ether, meant to bypass the normal fuel system and provide an easily ignitable vapor directly to the engine. If it’s not working, the problem lies either in the ignition system, compression, or an overabundance of fuel preventing proper combustion. Here’s a breakdown of five expert fixes, going beyond the obvious and digging into the technical aspects of each.

1. The Spark: Ignition System Check

The ignition system is the heart of any gasoline engine. It’s responsible for creating the spark that ignites the fuel-air mixture in the combustion chamber. If the spark is weak, intermittent, or nonexistent, even starting fluid won’t help.

• The Basics: The system consists of the spark plug, ignition coil, magneto (in many chainsaws), and wiring.
• My Experience: I recall a time when my old Stihl 026 wouldn’t start, despite repeated attempts with starting fluid. I meticulously checked the fuel lines and carburetor, only to find the problem was a cracked spark plug insulator. A seemingly minor issue, but it completely prevented the engine from firing.
• Technical Data Point: A healthy spark plug should produce a bright blue spark that jumps a gap of at least 6mm (0.24 inches) in open air. This tests the coil’s ability to generate sufficient voltage.

Step-by-Step Diagnosis

1. Spark Plug Inspection:
   • Visual Check: Remove the spark plug and inspect it. Look for cracks in the insulator, excessive carbon buildup, or oil fouling. A wet spark plug after repeated starting attempts can indicate flooding.
     • Technical Requirement: The spark plug gap should be within the manufacturer’s specified range, typically 0.5mm to 0.7mm (0.020 to 0.028 inches). Use a spark plug gapping tool to adjust the gap accordingly.
     • Data Point: A blackened, sooty spark plug indicates a rich fuel mixture, while a white or light gray plug suggests a lean mixture.
   • Spark Test: Reconnect the spark plug to the spark plug wire and ground the plug against the engine block. Pull the starter cord. Observe the spark. It should be a strong, blue spark. A weak, yellow spark or no spark at all indicates a problem.
     • Safety Note: Be careful not to touch the spark plug wire while pulling the starter cord, as this can result in an electric shock.
2. Ignition Coil Test:
   • Resistance Test: Use a multimeter to test the resistance of the ignition coil. Refer to your chainsaw’s service manual for the specific resistance values. An open circuit or a resistance value outside the specified range indicates a faulty coil.
     • Technical Requirement: The primary resistance of the coil is typically very low (e.g., 0.5-2 ohms), while the secondary resistance is much higher (e.g., 3-10k ohms).
     • Tool Requirement: A digital multimeter with accurate resistance measurement capability.
   • Air Gap Adjustment: Check the air gap between the ignition coil and the flywheel. This gap is crucial for proper ignition timing.
     • Technical Requirement: The air gap is typically very small, around 0.2mm to 0.4mm (0.008 to 0.016 inches). Use a feeler gauge to adjust the gap.
     • Practical Tip: A business card can often be used as a makeshift feeler gauge for setting the air gap. However, always refer to the manufacturer’s specifications for accurate settings.
3. Wiring and Connections:
   • Visual Inspection: Check all wiring connections for corrosion, damage, or loose connections.
   • Continuity Test: Use a multimeter to test the continuity of the wiring harness. A break in the wiring can prevent the spark from reaching the spark plug.

Case Study: Stihl MS271 Ignition Failure

I worked on a Stihl MS271 that had completely lost spark. The owner had tried everything, including starting fluid, with no luck. After performing the tests above, I found that the ignition coil had completely failed. The primary winding was open, indicating a breakdown in the coil’s internal insulation. Replacing the coil restored the spark and the saw fired right up. This highlights the importance of systematically testing each component of the ignition system.

2. The Breath: Compression Check

Compression is the squeezing of the air-fuel mixture inside the cylinder before ignition. Low compression means the mixture isn’t properly compressed, making ignition difficult or impossible, even with starting fluid.

• The Basics: Compression is created by the piston moving up the cylinder, sealing against the cylinder walls via the piston rings.
• My Experience: I once helped a friend troubleshoot his Husqvarna 455 Rancher. He’d abused it for years, never maintaining the air filter. The result? A scored cylinder wall and worn piston rings, leading to virtually no compression. Starting fluid made no difference.
• Technical Data Point: A healthy chainsaw engine should have a compression reading of at least 100 PSI (pounds per square inch). Some high-performance saws may require 120 PSI or higher.

Step-by-Step Diagnosis

1. Compression Test:
   • Procedure: Remove the spark plug and screw in a compression tester. Pull the starter cord several times while observing the gauge.
     • Tool Requirement: A compression tester specifically designed for small engines.
     • Safety Note: Wear safety glasses during the compression test to protect your eyes from any debris that may be ejected from the spark plug hole.
   • Reading Interpretation: Compare the compression reading to the manufacturer’s specifications. A reading below the minimum indicates a compression problem.
     • Technical Requirement: The compression reading should be consistent across multiple pulls of the starter cord. A fluctuating reading can indicate a leaky valve or piston rings.
2. “Wet” Compression Test:
   • Procedure: If the compression reading is low, inject a small amount of oil (e.g., 5-10ml) into the cylinder through the spark plug hole. Repeat the compression test.
     • Technical Rationale: The oil will temporarily seal any leaks in the piston rings, improving the compression reading.
   • Reading Interpretation:
     • If the compression reading increases significantly after adding oil, it indicates worn piston rings.
     • If the compression reading remains low, it suggests a problem with the valves or cylinder head gasket.
3. Visual Inspection (If Compression is Low):
   • Spark Plug Hole Examination: Use a flashlight to inspect the cylinder wall through the spark plug hole. Look for scoring or damage.
   • Exhaust Port Examination: Remove the muffler and inspect the piston and cylinder wall through the exhaust port.

Case Study: Poulan Pro Cylinder Scoring

I worked on a Poulan Pro chainsaw that had extremely low compression (around 60 PSI). The owner admitted to running the saw without oil for a short period. Upon inspection through the exhaust port, I found significant scoring on the cylinder wall. The piston rings were also worn and damaged. This type of damage is often irreparable, requiring a complete engine replacement. This demonstrates the critical importance of proper lubrication.

3. The Fuel: Flooding and Fuel Contamination

While starting fluid bypasses the normal fuel system, an overabundance of fuel in the cylinder (flooding) can still prevent ignition. Similarly, contaminated fuel can also render the starting fluid ineffective.

• The Basics: Flooding occurs when too much fuel is delivered to the cylinder, creating a mixture that is too rich to ignite. Fuel contamination can introduce water, dirt, or other substances that interfere with combustion.
• My Experience: I once spent hours trying to start a chainsaw that I thought had a faulty ignition system. It turned out the fuel tank had a small crack, allowing water to seep in. Even with starting fluid, the engine sputtered and coughed but wouldn’t start.
• Technical Data Point: Gasoline typically has a shelf life of 3-6 months. After that, it can start to degrade, forming gums and varnishes that can clog fuel lines and carburetor jets.

Step-by-Step Diagnosis

1. Flooding Check:
   • Symptoms: A strong smell of gasoline, a wet spark plug, and a gurgling sound when pulling the starter cord are all signs of flooding.
   • Procedure:
     • Remove the spark plug and pull the starter cord several times to clear excess fuel from the cylinder.
     • Allow the cylinder to air out for a few minutes.
     • Reinstall the spark plug and try starting the saw without using starting fluid.
2. Fuel Inspection:
   • Visual Inspection: Drain a small amount of fuel from the fuel tank into a clear container. Look for water, dirt, or other contaminants.
   • Smell Test: Smell the fuel. Stale or sour-smelling fuel should be discarded.
   • Fuel Filter Check: Inspect the fuel filter for clogs or damage. Replace the filter if necessary.
     • Technical Requirement: Fuel filters should be replaced regularly, typically every 3-6 months, depending on usage.
3. Carburetor Inspection (If Flooding Persists):
   • Needle Valve Check: The needle valve controls the flow of fuel into the carburetor. A faulty needle valve can leak, causing flooding.
   • Float Adjustment: The float regulates the fuel level in the carburetor bowl. An improperly adjusted float can cause flooding.
     • Technical Requirement: The float height should be set according to the manufacturer’s specifications.
     • Tool Requirement: A carburetor adjustment tool may be required to properly adjust the float.

Case Study: Contaminated Fuel in a Ryobi Chainsaw

A customer brought in a Ryobi chainsaw that wouldn’t start. He had left the saw sitting in his garage for over a year with fuel in the tank. The fuel had degraded, forming a thick, gummy residue that clogged the fuel lines and carburetor. The starting fluid was ineffective because it couldn’t mix properly with the contaminated fuel. Cleaning the fuel system and replacing the fuel filter resolved the issue. This underscores the importance of using fresh fuel and properly storing your chainsaw.

4. The Air: Air Filter and Exhaust Blockage

While seemingly simple, a severely clogged air filter or a blocked exhaust port can significantly restrict airflow, preventing the engine from starting, even with starting fluid.

• The Basics: The air filter prevents dirt and debris from entering the engine, while the exhaust port allows exhaust gases to escape.
• My Experience: I once spent an afternoon wrestling with a chainsaw that refused to start. I’d overlooked the obvious: a completely clogged air filter packed with sawdust. Starting fluid did nothing because the engine couldn’t “breathe.”
• Technical Data Point: A clean air filter can improve fuel efficiency by up to 10%.

Step-by-Step Diagnosis

1. Air Filter Inspection:
   • Visual Inspection: Remove the air filter and inspect it for dirt, debris, or damage.
   • Cleaning: Clean the air filter with compressed air or warm, soapy water. Allow the filter to dry completely before reinstalling it.
     • Technical Requirement: Air filters should be cleaned regularly, typically after every 5-10 hours of use.
     • Material Specification: Some air filters are made of foam, while others are made of paper or felt. Follow the manufacturer’s recommendations for cleaning and maintenance.
2. Exhaust Port Inspection:
   • Visual Inspection: Remove the muffler and inspect the exhaust port for carbon buildup or obstructions.
   • Cleaning: Use a scraper or wire brush to remove carbon buildup from the exhaust port.
     • Safety Note: Wear safety glasses and gloves when cleaning the exhaust port, as carbon buildup can be irritating to the skin and eyes.
3. Spark Arrestor Screen Inspection:
   • Location: The spark arrestor screen is typically located in the muffler.
   • Cleaning: Clean the spark arrestor screen with a wire brush to remove carbon buildup.
     • Technical Requirement: The spark arrestor screen should be cleaned regularly to prevent exhaust restrictions and reduce the risk of wildfires.

Case Study: Exhaust Blockage in a McCulloch Chainsaw

I encountered a McCulloch chainsaw that had a severely blocked exhaust port. The owner had been using the saw for years without ever cleaning the exhaust port or spark arrestor screen. The buildup of carbon deposits had completely restricted the flow of exhaust gases, preventing the engine from starting. Cleaning the exhaust port and spark arrestor screen restored proper airflow and the saw started easily. This emphasizes the importance of regular maintenance.

5. The Mechanical: Shear Key and Flywheel Issues

The shear key, also known as a flywheel key, is a small, inexpensive part that connects the flywheel to the crankshaft. It’s designed to shear (break) if the chainsaw blade hits a solid object, preventing damage to the engine. If the shear key is broken, the ignition timing will be off, preventing the engine from starting, even with starting fluid.

• The Basics: The flywheel contains magnets that generate the electrical current for the ignition system. The shear key ensures that the flywheel is properly aligned with the crankshaft.
• My Experience: I remember a time when I was cutting firewood and accidentally hit a hidden rock with my chainsaw blade. The saw immediately stalled. I initially suspected a fuel problem, but after checking everything else, I discovered that the shear key had sheared.
• Technical Data Point: Shear keys are typically made of aluminum or a soft metal alloy to ensure they break before more expensive engine components are damaged.

Step-by-Step Diagnosis

1. Flywheel Inspection:
   • Removal: Remove the starter assembly and flywheel cover.
   • Visual Inspection: Inspect the flywheel for damage or cracks.
2. Shear Key Inspection:
   • Location: The shear key is located between the flywheel and the crankshaft.
   • Visual Inspection: Inspect the shear key for signs of damage or breakage.
   • Replacement: If the shear key is broken, replace it with a new one.
     • Technical Requirement: Use the correct shear key for your chainsaw model.
     • Tool Requirement: A flywheel puller may be required to remove the flywheel.
3. Flywheel Alignment:
   • Procedure: Ensure that the flywheel is properly aligned with the crankshaft before tightening the flywheel nut.
     • Technical Requirement: The flywheel should be aligned according to the manufacturer’s specifications.

Case Study: Shear Key Failure in a Craftsman Chainsaw

A customer brought in a Craftsman chainsaw that wouldn’t start. He had been cutting a large tree when the saw suddenly stopped. After inspecting the saw, I found that the shear key had sheared. The impact of the blade hitting a knot in the wood had caused the shear key to break. Replacing the shear key restored the ignition timing and the saw started immediately. This illustrates the importance of the shear key as a safety device.

Final Thoughts

Troubleshooting a chainsaw that won’t start, even with starting fluid, can be a frustrating experience. However, by systematically checking the ignition system, compression, fuel system, air intake, and mechanical components, you can usually diagnose and resolve the issue. Remember to always refer to your chainsaw’s service manual for specific instructions and specifications. And most importantly, always prioritize safety when working on power equipment. Wood processing and logging can be incredibly rewarding, but only when approached with knowledge, respect, and a commitment to safe practices.

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