Spring is here, but your lawn mower won’t start, sputters, or simply refuses to work after sitting all winter? You’re not alone—this is one of the most common issues homeowners face each spring. Cold, moisture, stale fuel, and lack of off-season maintenance are the main culprits, but the good news is that most “won’t work after winter” problems are easy to fix at home with basic tools. This step-by-step guide will walk you through every cause and solution so you can get your mower running strong for the season ahead.
Quick-Check: Why Won’t My Mower Work After Winter?
- Old, stale, or contaminated gasoline left in the tank
- Carburetor jets or float gummed up from old fuel
- Fouled, corroded, or worn spark plug
- Dead or weak battery (for electric start or battery-powered models)
- Dirty or clogged air filter
- Clogged fuel filter or collapsed fuel line
- Primer bulb cracked or not working (if equipped)
- Blade or deck jammed with grass, ice, or debris
- Safety switches not engaged or stuck
- Mouse nests, chewed wires, or debris under the engine shroud
- Flooded engine after repeated start attempts
- Corroded wiring or connectors (electric mowers)
1. Replace Old Fuel and Clean the Tank
- Gas left in the tank or carburetor over winter quickly goes stale and clogs the fuel system.
- Drain all old fuel from the tank with a siphon or turkey baster. Dispose of it safely.
- Wipe out or rinse the tank if you see rust, sludge, or water droplets. Dry thoroughly before adding new fuel.
- Refill with fresh, clean gasoline—preferably ethanol-free or with stabilizer added.
- Start each season with a clean tank to avoid carburetor and starting issues.
2. Clean or Rebuild the Carburetor
- Gummed-up jets and stuck floats are top causes for no-start after winter.
- Spray carburetor cleaner into the carb’s air intake and try to start. If it fires briefly, the carb is likely clogged.
- Remove the carburetor bowl and clean all jets, float, and needle with carb cleaner and compressed air.
- For severe gumming, remove and fully rebuild or replace the carburetor using an inexpensive kit.
- Check all gaskets and seals for cracks and replace if needed.
3. Replace or Clean the Spark Plug
- Remove the spark plug using a plug wrench. Inspect for black soot, rust, oil, or damage.
- Clean a lightly fouled plug with a wire brush. Replace if it’s heavily fouled, corroded, or more than one year old.
- Set the gap to your engine’s specification (usually 0.028–0.030 inches).
- Reinstall and reconnect the plug wire firmly.
4. Battery & Electrical Checks (Electric Start & Cordless Models)
- Charge batteries fully before first use after storage. Weak or dead batteries are very common after winter.
- Clean corroded terminals with a wire brush or baking soda solution.
- Replace batteries that won’t hold a charge or are more than 3–4 years old.
- For corded mowers, check extension cords, outlets, and reset any tripped GFCI or breakers.
- Inspect for chewed or corroded wiring—common after storage in sheds or garages with rodents.
5. Air Filter: Clean or Replace
- Remove and inspect the air filter—dirt and dust collect during storage.
- Tap foam filters to remove dirt, wash with soapy water, dry, and oil lightly before reinstalling. Replace paper filters if dirty or torn.
- Test start briefly without the filter (just for diagnosis)—if it starts, replace the filter before mowing.
6. Fuel Filter and Line
- Inspect the fuel line for cracks, collapse, or blockages—replace as needed.
- Replace the fuel filter if it’s dirty or fuel flows slowly through it.
- Check the gas cap vent is clear—blocked vents can cause vacuum in the tank, stopping fuel flow.
7. Primer Bulb & Choke
- Press the primer bulb 2–3 times before starting (if equipped). Replace if it’s cracked or doesn’t fill with fuel.
- Set the choke to ON for the first start of the season. Move to OFF once the engine runs smoothly.
8. Safety Switches and Controls
- Check all safety features: handlebar lever, blade control, seat switch (riding), or brake pedal (if equipped).
- Release and re-engage all controls to “wake up” sticky or frozen switches after storage.
- Replace faulty switches to ensure safe and reliable starting.
9. Mechanical Jams: Blade, Deck, and Engine
- Disconnect spark plug or remove battery before checking under the deck.
- Look for frozen grass, leaves, sticks, or ice jams under the blade or around the deck.
- Spin the blade by hand (wear gloves)—it should move freely. Free any jams before trying to start again.
- Check for rodent nests or debris under the engine cover, which can interfere with cooling or wiring.
10. Flooded Engine? Here’s What to Do
- If you smell gas or the spark plug is wet, the engine may be flooded from too many start attempts.
- Remove the spark plug and let it dry. Pull the starter cord several times to clear extra fuel.
- Reinstall the plug and try starting with no choke or primer.
Preventive Maintenance: For Easy Spring Starts
- Run the engine dry or add fuel stabilizer before winter storage
- Change oil, air filter, and spark plug every season
- Charge or disconnect batteries and store indoors
- Store mower in a dry, rodent-proof location
- Clean deck and under covers before storage
- Check for nests and chewed wiring before the first spring use
Frequently Asked Questions (FAQ)
Why won’t my mower start after sitting all winter?
Most often, the problem is old fuel, carburetor clogs, fouled spark plug, dead battery, or stuck safety switches. Follow the steps above for a fast diagnosis.
How do I clean the carburetor after storage?
Remove and disassemble the carb, soak all parts in carb cleaner, clean jets and passages with compressed air, and reassemble with new gaskets.
Do I need to change the oil every spring?
Yes—fresh oil is critical for a healthy engine and easy starting. Change the oil before the first mow of the year.
My battery mower won’t power on after winter—what now?
Charge the battery fully, clean the terminals, and check for rodent-damaged wiring. Replace old or dead batteries as needed.
When should I call a repair shop?
If you’ve checked fuel, spark, air, battery, and safety switches but it still won’t work—or you suspect engine or major wiring damage—it’s time for a pro.
Conclusion: Get Your Mower Working After Winter Storage
A lawn mower that won’t work after winter is almost always the result of old fuel, gummed-up carburetor, a fouled spark plug, dead battery, or simple mechanical or wiring issues. With these troubleshooting steps, you can get your mower running strong in minutes. Practice a little off-season maintenance, and you’ll enjoy easy starts and a beautiful lawn, season after season!
Ready to mow? Use this guide to fix your mower after winter and enjoy a healthy yard all spring and summer!