Nothing is more frustrating than pulling your lawn mower out for the first cut of the season—only to find it just won’t start. Whether you have a push mower, riding mower, or electric model, starting problems are among the most common headaches for homeowners. The good news? Most “won’t start” issues are easy to diagnose and fix at home. This comprehensive guide walks you through every major cause and practical solution so you can get back to mowing fast.
Quick-Check: Why Won’t My Lawn Mower Start?
- Stale or old gasoline in the tank
- Empty fuel tank or clogged fuel line/filter
- Dirty or fouled spark plug
- Dead battery (for electric start or cordless models)
- Clogged or dirty air filter
- Carburetor issues (gummed up jets, stuck float, or needle)
- Primer bulb not working (if equipped)
- Safety switches not engaged (seat, blade, handle, etc.)
- Engine flooded (from too many failed start attempts)
- Mechanical jams—blade stuck or engine seized
- Choke or throttle not set correctly
- Rodent damage or wiring issues (after winter storage)
1. Check the Fuel: Fresh Gasoline is Key
- Always drain old gas and replace with fresh if your mower has sat unused for more than 30 days.
- Look for water or debris in the tank. Clean and refill if needed.
- Check the fuel line for cracks, leaks, or clogs. Replace if fuel won’t flow easily.
- Replace the fuel filter annually or if it looks dirty or slow to flow.
- Ensure the gas cap vent is not blocked—this can cause vacuum and prevent fuel flow.
2. Inspect and Replace the Spark Plug
- Remove the plug and check for black soot, rust, or wear. Clean lightly with a wire brush, or replace if fouled or old.
- Set the gap to the manufacturer’s spec (usually 0.028–0.030 inches).
- Reconnect the plug wire firmly after reinstalling.
- If the plug is wet with gas, the engine may be flooded—see section below.
3. Clean or Replace the Air Filter
- A clogged air filter prevents proper airflow and can stop the mower from starting.
- Remove the filter and check for dirt or oil. Clean foam filters with soapy water, dry, and oil lightly; replace paper filters if dirty.
- Try starting the mower without the filter (just for a brief test). If it starts, replace the filter before regular use.
4. Test the Battery (Electric Start & Cordless Models)
- Charge the battery fully before trying to start.
- Check terminals for corrosion and clean if needed. Replace batteries that won’t hold a charge.
- Test your charger by plugging into a different outlet.
- If your mower is corded electric, check the power cord, outlet, and reset any tripped breakers or GFCI outlets.
5. Check the Carburetor
- Spray carburetor cleaner into the carburetor throat with the engine off. If it starts briefly, the carb is likely gummed up.
- Remove the carb bowl and clean jets, float, and needle with carburetor cleaner and compressed air.
- For severe clogging, rebuild or replace the carburetor (kits are affordable for most models).
6. Primer Bulb & Choke Settings
- Press the primer bulb 2–3 times before starting (if equipped). Replace if it’s cracked or never fills with fuel.
- Ensure the choke is ON for cold starts. Move to OFF after the engine starts.
7. Safety Switches and Controls
- Check that all safety features (handle bar, seat switch, blade control, brake pedal) are properly engaged.
- On many mowers, releasing or not fully engaging these switches will prevent starting.
- Wiggle levers and handles to ensure switches make full contact. Replace faulty switches if needed.
8. Flooded Engine? Here’s What to Do
- If you smell gas or the plug is wet, the engine may be flooded from repeated start attempts.
- Remove the spark plug and let it air dry for 10–15 minutes. Pull the starter cord several times to clear excess fuel from the cylinder.
- Reinstall the plug and try again without using the choke or primer.
9. Mechanical Jams & Deck Obstructions
- Disconnect the spark plug, then check under the deck for stuck grass, sticks, or debris.
- Spin the blade by hand (with gloves)—it should turn freely. If not, clear any obstructions.
- For riding mowers, ensure the transmission is in Neutral or Park.
10. Special Note for Battery & Corded Electric Mowers
- Check battery charge, seating, and clean terminals.
- Test the safety key, handle lock, and all interlock switches.
- Inspect the blade and deck for jams, which can trigger motor protection circuits.
- Allow overheated mowers to cool down before restarting.
Preventive Maintenance: Avoid Starting Problems Next Time
- Use only fresh fuel; add stabilizer for storage
- Replace air filter, spark plug, and fuel filter every spring
- Clean or rebuild carburetor annually
- Charge and store batteries indoors
- Inspect all safety switches and controls before every mow
- Keep the mower deck clean and store in a dry location
Frequently Asked Questions (FAQ)
Why does my mower crank but not start?
Most often, this is due to bad fuel, a dirty carburetor, fouled spark plug, clogged air filter, or lack of spark. Follow the checklist above for easy diagnosis.
How do I know if my spark plug is bad?
A bad plug will appear fouled, black, rusty, or have a worn electrode. Replace if in doubt—it’s cheap insurance for easy starts.
Why won’t my electric mower power on?
Check the battery charge, seating, and contacts. For corded models, check your outlet, cord, and reset any breakers or GFCI outlets.
How do I avoid flooding the engine?
Don’t over-prime or over-choke. If the engine won’t start, wait a few minutes, dry the spark plug, and try again without priming.
When should I call a repair shop?
If you’ve checked fuel, spark, air, and safety switches but the mower still won’t start—or if you suspect internal damage—it’s time to call a pro.
Conclusion: Get Back to Mowing Fast
Most lawn mower starting problems are solved with simple checks: fresh fuel, a clean carburetor, a good spark plug, and a working air filter. Stay ahead with routine maintenance and proper storage, and your mower will start up easily all season long. Don’t let a stubborn mower keep you from a beautiful lawn—use these tips, and you’ll be cutting grass again in no time!
Ready for a trouble-free start? Follow these steps, and your mower will be running strong all year long!