Few things are as frustrating as getting your lawn mower to start—only to have it stall or die within seconds. Whether your mower sputters and quits, runs for a minute and stops, or only stays running with the choke on, you’re not alone. This issue is very common across all mower types—walk-behind, self-propelled, riding, gas, and even battery-powered models. The good news? Most causes are simple, and with a little troubleshooting, you can get your mower running strong again.
Quick-Check: Why Does My Lawn Mower Start and Then Die?
- Dirty or clogged carburetor
- Old, stale, or contaminated gasoline
- Blocked or dirty fuel filter
- Clogged air filter
- Bad or fouled spark plug
- Gummed-up fuel line or faulty gas cap (not venting)
- Fuel not reaching the carburetor or engine (fuel starvation)
- Primer bulb or choke issues (not working or set wrong)
- Stuck or dirty main jet in the carburetor
- Faulty ignition coil or safety switches (rare but possible)
- For battery mowers: Low battery or failing electronics
1. Fuel System: The Most Common Culprit
- Old Gas: Gasoline degrades in as little as 30 days. Always start the season with fresh, clean fuel. Drain old gas from the tank and carburetor if your mower sat unused.
- Clogged Fuel Filter or Line: A dirty filter or blocked fuel line prevents enough fuel from reaching the engine. Replace filters every season and check lines for kinks, cracks, or blockages.
- Carburetor Gumming: Old fuel leaves sticky deposits in the carburetor, blocking jets and float valves. Spray carburetor cleaner into the air intake and try starting. If it briefly runs and dies, the carb likely needs a thorough cleaning or rebuild.
- Fuel Cap Not Venting: If the gas cap vent is blocked, a vacuum forms in the tank and fuel flow stops. Loosen the cap and restart—if it keeps running, replace the cap.
2. Air Filter: Don’t Let Your Mower Choke
- A clogged or dirty air filter can cause your mower to run rough and die after starting.
- Remove and inspect the filter. Clean foam filters with soapy water, dry, and oil lightly. Replace paper filters if dirty or discolored.
- Test start without the air filter (for a few seconds only). If it runs better, install a new filter before mowing.
3. Spark Plug: Simple but Critical
- Remove the spark plug and inspect for fouling, black soot, rust, or worn electrode.
- Clean lightly with a wire brush or replace with a new, correctly gapped plug (usually 0.028–0.030 inches for most mowers).
- Ensure the spark plug wire fits snugly on the plug.
- Weak spark can cause the mower to start but not keep running, especially under load.
4. Carburetor Issues: Cleaning and Adjustments
- If your mower starts and dies unless the choke is ON, your carburetor’s main jet or emulsion tube is probably clogged.
- Remove the carburetor bowl and spray cleaner through all jets and passages. Use compressed air for stubborn clogs.
- If cleaning doesn’t work, rebuild or replace the carburetor. Rebuild kits are affordable for most models.
- Check and replace all carburetor gaskets and seals during cleaning or rebuild.
5. Primer Bulb & Choke: Start Settings Matter
- Press the primer bulb 2–3 times before starting if equipped. Replace any bulb that’s cracked, leaking, or doesn’t fill with fuel.
- Set the choke ON for cold starts. If the engine dies as soon as you turn off the choke, suspect carburetor or fuel delivery issues.
6. Fuel Starvation: Check for Blockages
- Disconnect the fuel line at the carburetor. Place the end in a cup and turn the fuel valve ON (if equipped)—fuel should flow freely.
- If flow is weak or absent, check the tank, line, and filter for obstructions or replace them if needed.
- If fuel reaches the carburetor but the engine still dies, focus on cleaning or rebuilding the carb.
7. Safety Switches and Electrical Issues
- Some mowers have safety switches on the handle, blade control, seat (riding), or brake. If any are loose, faulty, or disengaged, the mower may start then shut off.
- Test all switches by wiggling and re-engaging. Replace faulty switches promptly.
- Check the ignition coil (especially if there is no spark after it dies). Replace if weak or intermittent.
8. Battery/Electric Mowers: Charge & Connections
- Low battery charge or failing battery pack can cause your electric or cordless mower to start but die quickly.
- Charge fully before each mow. Replace old or weak batteries and clean all contacts.
- Check for loose or corroded wiring, especially after winter storage.
9. Other Mechanical Issues
- Seized or stuck blade, debris under the deck, or a bent crankshaft can all cause the engine to bog and stall after starting.
- Disconnect the spark plug, tip the mower, and check for blockages or blade damage before starting again.
- Inspect engine oil level (if applicable)—very low oil can trigger safety shutdowns on some models.
Preventive Maintenance: Keep Your Mower Running Smoothly
- Use fresh, stabilized fuel every season
- Replace air filter, spark plug, and fuel filter yearly
- Clean or rebuild the carburetor annually if used heavily
- Clean mower deck and blade after every few mows
- Store mower in a dry, rodent-proof place during the off-season
- Charge and store batteries indoors for electric models
Frequently Asked Questions (FAQ)
Why does my mower start, then die when I turn off the choke?
This almost always means the carburetor’s main jet is clogged—so the engine can’t get enough fuel without the extra enrichment from the choke. Clean or rebuild the carburetor for a reliable fix.
Why does my mower stall after running for a minute?
Likely fuel starvation from a clogged filter, fuel line, or bad gas cap vent. Also check for dirty air filter or carburetor issues.
Can a bad spark plug cause my mower to die after starting?
Yes—a fouled or weak spark plug can cause misfiring, stalling, and hard starts. Replace it if it looks dirty, worn, or old.
What if my battery mower starts, then stops immediately?
Charge or replace the battery, check for overheated motor, and inspect connections for corrosion or loose wires.
When should I call a repair shop?
If you’ve cleaned the carburetor, checked fuel, spark, and air, but the mower still dies—especially if you hear knocking or suspect internal engine problems—consult a professional.
Conclusion: Keep Your Mower Running Strong All Season
A mower that starts and dies is almost always suffering from a fuel, air, or spark issue—most of which are quick and easy to fix at home. Use this troubleshooting guide to find the problem, apply regular maintenance, and your mower will stay running reliably for years to come. Enjoy a lush, healthy lawn and hassle-free mowing all season!
Ready for a smooth-running mower? Fix the stalling—and enjoy your yard work again!