Lawn Mower Won’t Start After Winter? 5 Common Fixes

If your lawn mower won’t start after winter, it’s a common issue often caused by old fuel, a dirty carburetor, a fouled spark plug, a dead battery, or a clogged air filter. Addressing these five areas systematically can usually get your mower running again without a trip to the repair shop.

Check the Fuel and Fuel System

Old gasoline is the most frequent culprit for a mower that won’t start after storage. Gasoline can degrade and separate over several months, leading to clogs in the fuel lines and carburetor. Drain any old fuel from the tank and replace it with fresh, stabilized gasoline. If the fuel lines appear clogged, you might need to clean or replace them. Ensure the fuel filter, if present, isn’t blocked; a dirty fuel filter restricts fuel flow to the engine. For expert lawn mower reviews on this site.

Inspect and Clean the Carburetor

A dirty carburetor is another prime suspect. Residue from old fuel can gum up the carburetor’s jets and passages, preventing proper fuel-air mixture. You can try a carburetor cleaner spray, following the product instructions, to dissolve deposits. For more stubborn clogs, you may need to remove and disassemble the carburetor for a thorough cleaning. This often involves soaking parts in a specialized carburetor cleaning solution and using fine wire to clear tiny orifices.

Examine and Replace the Spark Plug

A fouled or worn-out spark plug can prevent the engine from igniting the fuel. Remove the spark plug and inspect it. Look for signs of carbon buildup, oil, or damage to the electrode. If it’s dirty, try cleaning it with a wire brush. If it looks corroded, cracked, or excessively worn, it’s best to replace it with a new one of the correct type for your mower. Always ensure the gap is set correctly according to your mower’s manual.

Test the Battery and Charging System

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For mowers with electric start, a dead or weak battery will prevent the engine from turning over. Use a multimeter to check the battery’s voltage; it should typically read around 12.6 volts for a fully charged 12-volt battery. If it’s low, try charging it. If the battery doesn’t hold a charge, it likely needs replacement. Also, check the battery terminals for corrosion and clean them if necessary to ensure good electrical contact.

Verify the Air Filter and Other Essentials

A clogged air filter can restrict airflow to the engine, making it difficult to start. Remove the air filter and inspect it. If it’s dirty or clogged, clean or replace it. Paper filters are usually replaced, while foam filters can sometimes be washed and re-oiled. Additionally, ensure the oil level is correct, as some mowers have low-oil sensors that prevent starting. Finally, check that all safety switches (like those on the handle or seat) are engaged properly.

• Always use fresh, stabilized fuel for optimal performance.
• Regularly clean or replace your air filter to ensure proper engine breathing.
• Inspect your spark plug annually and replace it if signs of wear are present.
• Keep your mower’s battery charged during off-season storage.
• Consider a fuel stabilizer when storing your mower for extended periods.

By systematically checking these five common areas, you can often diagnose and fix why your lawn mower won’t start after winter. If these steps don’t resolve the issue, it might be time to consult a professional mechanic for more complex problems like valve adjustments or internal engine issues.