Chainsaw No Spark: Causes and Solutions

Chainsaw No Spark: Causes and Solutions

As a chainsaw owner, nothing is more frustrating than pulling the starter rope and getting no spark. Without that critical spark, the engine won’t start and you can’t get your cutting work done. When your trusty chainsaw suddenly has no spark, it’s time to do some diagnosing and get the issue fixed. In this blog post, I’ll provide a comprehensive guide to determine why your chainsaw has no spark and the steps to get it running again.

Common Causes of No Spark in a Chainsaw

Chainsaw No Spark: Causes and Solutions

The ignition system in a chainsaw is responsible for generating the high voltage spark that ignites the fuel-air mixture in the combustion chamber. Here are some of the most frequent culprits when there’s no spark in your chainsaw:

Dirty or Faulty Spark Plug

The spark plug is arguably the most important component in the ignition system. Over time, the electrodes can become coated with carbon buildup from the fuel residues or oil from the cylinder. This prevents the strong spark needed to ignite the engine. Inspecting and cleaning or replacing the spark plug is one of the first things to check when diagnosing a no spark issue.

Defective Ignition Coil

The ignition coil transforms the low voltage from the magneto into thousands of volts needed to jump the spark plug gap. If the coil is damaged or defective, it won’t be able to properly amplify the voltage, resulting in a weak spark or no spark at all. Testing the ignition coil usually involves checking resistance values.

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Damaged Spark Plug Wire

The spark plug wire or lead carries the high voltage from the ignition coil to the spark plug. If the wire is cracked or damaged, the spark can leak out or fail to reach the plug altogether. Carefully inspect the wire insulation and connectors to uncover any visible damage.

Cracked Distributor Cap

On some chainsaw models, the ignition system includes a distributor cap that routes the spark to the correct cylinder. Cracks or carbon tracks in the distributor cap can allow the high voltage spark to dissipate, preventing it from reaching the spark plug.

Improper Fuel Mixture

Running the chainsaw engine on the wrong fuel mixture can lead to a host of problems, including fouled spark plugs and buildup in the combustion chamber over time. Always use fresh fuel and the proper oil-to-gas ratios indicated in the owner’s manual.

Carburetor Issues

A dirty, clogged, or improperly adjusted carburetor can impact the fuel-air mixture and ignition timing. This may prevent starting or cause intermittent no spark problems. A thorough carburetor inspection and cleaning may be needed to restore normal engine operation.

Step-by-Step Guide to Fixing Chainsaw No Spark

If your chainsaw won’t start and you suspect a no spark issue, follow these helpful steps to diagnose and correct the problem:

1. Check for Spark

The first step is confirming that there is indeed no spark present. Remove the spark plug and reattach the wire. Rest the threaded portion of the spark plug against the engine cylinder and pull the starter cord briskly. Look for a bright blue spark as the electrode hits the cylinder. Be very careful not to touch the electrode as the voltage can shock you. If there is no spark, move on to the next steps.

2. Inspect and Clean/Replace the Spark Plug

Examine the spark plug electrodes for excessive carbon deposits or other fouling. Use a wire brush to gently clean any debris from between the electrodes and center electrode insulator. Check that the spark plug gap is properly set, usually around 0.020-0.030 inches for chainsaw engines. Replace the spark plug with the recommended model if it’s excessively worn.

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3. Check the Ignition Coil

Use a multimeter to test the ignition coil resistance values per the service manual specifications. Compare the readings to factory values to determine if the coil is faulty. Replace the coil if it’s outside the specified ohms range. Make sure all connections are clean and secure.

4. Examine Spark Plug Wire and Connections

Carefully inspect the entire length of the spark plug wire, looking for any chafing, cuts, or deterioration of the insulation. Make sure the connections at both ends are tight and free of corrosion. Replace the wire if any damage is found.

5. Test and Replace Distributor Cap

If your model has a distributor cap, check for cracks, carbon tracking marks, corrosion, and moisture inside. Use an ohmmeter to check for continuity between the tower terminals. No continuity indicates current leakage. Replace the distributor cap if faulty.

6. Adjust Fuel Mixture

Consult your owner’s manual for the proper fuel mixture ratio. Use only fresh, high-quality gas and two-stroke oil. Never use stale fuel! Adjust the carburetor settings per instructions if needed to achieve the correct fuel ratio.

7. Clean/Rebuild Carburetor

If adjusting the carb doesn’t help, disassemble the carburetor to clean passageways, jets, and screens of any dirt, gummed-up fuel residue, or varnish buildup. Carefully reassemble and adjust per guidelines. Rebuild kits are available for very worn carburetors.

Preventing No Spark Chainsaw Problems

Here are some maintenance tips to help avoid no spark issues in your chainsaw:

  • Replace the spark plug annually or after 25 hours of use. Check that the replacement plug matches your chainsaw’s specifications.
  • Use only fresh fuel blended at the proper ratio. Stale fuel can gum up carburetors and cause deposits.
  • Clean the air filter regularly and replace when worn to allow proper airflow.
  • Keep the chainsaw engine exterior clean of debris, sawdust, and dirt, especially around the ignition coil and flywheel.
  • Periodically check all ignition system wires, connections, and components for damage or wear.
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Following the manufacturer’s recommendations for fuel, maintenance, and replacement parts will go a long way toward preventing problems with no spark in your chainsaw. But if it does occur, this guide will help troubleshoot the cause and get you back to sawing quickly. With proper care and maintenance, your chainsaw will provide many years of reliable service.


Losing spark in your chainsaw can be incredibly frustrating when you have wood to cut. But armed with some basic diagnostic and troubleshooting steps, you can determine the root cause and remedy many common no spark issues. Start by methodically checking components like the spark plug, ignition coil, plug wire, distributor cap, fuel mixture, and carburetor. Replace parts as needed and adjust settings to factory specifications. With regular maintenance and preventive care, you can avoid no spark problems and keep your chainsaw running smoothly for all your projects.

Frequently Asked Questions 

How often should I replace the spark plug on my chainsaw?

The spark plug is a wear item that should be replaced annually or every 25 hours of chainsaw run time. Use the exact plug model specified for your saw. Check the electrode gap and insulator condition regularly when cleaning the plug.

Can I use any spark plug brand in my chainsaw?

For optimal performance, always use the spark plug model recommended in your owner’s manual. Using the wrong plug can impact ignition timing, fuel efficiency, and engine power output. Stick with the specified plug.

How can I tell if my chainsaw ignition coil is faulty?

Test the ignition coil by checking resistance values with a multimeter. Compare the readings across the primary and secondary windings to manufacturer specifications. Significant deviation from the stated resistance range indicates a defective coil.

Can a clogged air filter cause my chainsaw to lose spark?

Yes, a dirty, clogged air filter can allow an overly rich fuel mixture to enter the engine. This can foul the spark plug and lead to weak ignition over time. Always replace air filters per the maintenance schedule.

What fuel ratio should I use in my chainsaw?

It’s crucial to use the exact gas to oil mixture specified for your chainsaw model. Most are in the range of 25:1 to 50:1, but check the owner’s manual for the proper fuel ratio and type of oil required. Never guess – incorrect fuel can cause spark plug fouling.

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