If your lawn mower starts but dies shortly after, you’re not alone—this is one of the most common headaches for mower owners, no matter the brand or type. Whether your mower runs for a few seconds or a minute before quitting, most issues come down to fuel, air, spark, or basic maintenance. Here’s a complete, step-by-step guide to diagnosing and fixing a mower that starts but won’t stay on, so you can get back to mowing and enjoy a beautiful, healthy yard.
Quick Picks: Why Does My Lawn Mower Start Then Die?
- Clogged Carburetor: Old fuel gums up the jets, letting the engine run on the primer shot but stall right after.
- Dirty or Blocked Air Filter: Chokes off airflow, causing the engine to stall out.
- Old, Stale, or Contaminated Gas: Poor-quality fuel can cause sputtering, surging, or quick stalling.
- Fouled or Damaged Spark Plug: A weak or inconsistent spark can’t keep the engine firing.
- Blocked Fuel Filter or Fuel Line: Fuel doesn’t flow steadily to the carburetor, so the engine dies once the bowl empties.
- Choke or Throttle Linkage Problems: Choke stays closed or doesn’t open properly, causing the engine to stall as it warms up.
- Vacuum Leaks or Bad Gaskets: Rare, but air leaks around the carb or intake can upset the fuel/air mix and kill the engine.
Buyer’s Guide: What You’ll Need to Troubleshoot & Repair
- Carburetor cleaner spray: For breaking down old fuel and gunk.
- Replacement air filter: Use the right type for your model.
- Fresh gasoline: Avoid old or watery fuel.
- New spark plug: Check your manual for the right plug and gap.
- Fuel line and fuel filter: For replacing blocked or damaged parts.
- Socket wrench & screwdriver set: For plug, filter, and carburetor access.
- Work gloves & eye protection: Always use safety gear when working on your mower.
Step-by-Step Guide: How to Fix a Lawn Mower That Starts Then Dies
1. Replace Old or Bad Gasoline
- Drain the tank and carburetor bowl completely using a siphon or by tilting the mower safely.
- Refill with fresh, clean gasoline (no more than 30 days old).
- Add a fuel stabilizer to help keep gas fresh longer if you mow infrequently.
2. Clean or Replace the Air Filter
- Remove the air filter cover and inspect the filter.
- If it’s dirty, clogged, or soaked with oil, replace it. Wash and dry foam filters if they’re in decent shape.
- A clean filter improves airflow, which is crucial for engine performance.
3. Clean the Carburetor
- Remove the air filter and spray carburetor cleaner into the intake or carb bowl.
- Let the cleaner sit for 5–10 minutes, then try starting the engine.
- If the mower still dies quickly, the carburetor may need to be removed and deep-cleaned or rebuilt.
- If you’re not comfortable doing this, most repair shops can clean or rebuild a carburetor affordably.
4. Check and Replace the Spark Plug
- Remove the spark plug with a socket and inspect for carbon deposits, oil, or cracks.
- Clean lightly with a wire brush or replace with a new, properly gapped spark plug.
- Make sure the spark plug wire is securely attached when reinstalling.
5. Inspect and Replace the Fuel Filter & Fuel Line
- Check the fuel line and in-line fuel filter for blockages, cracks, or kinks.
- Replace any damaged lines or dirty filters to ensure smooth fuel flow to the carburetor.
6. Adjust Choke and Throttle Linkages
- Ensure the choke closes for cold starts but opens fully as the engine warms up.
- Check throttle and choke cables for smooth movement and adjust or lubricate if needed.
7. Look for Gasket or Vacuum Leaks
- Inspect carburetor and intake gaskets for cracks or gaps that might let in extra air.
- Spray carb cleaner around the carb base while running—if RPM changes, you have a leak that needs sealing or gasket replacement.
Comparison Table: Why Lawn Mowers Start Then Die
| Problem | Solution | Difficulty | Parts Needed |
|---|---|---|---|
| Clogged Carburetor | Clean or rebuild carb | Easy-Medium | Carb cleaner, gaskets |
| Dirty Air Filter | Replace or clean filter | Easy | Air filter |
| Old or Bad Gas | Drain and refill with fresh gas | Easy | Gasoline |
| Bad Spark Plug | Clean or replace spark plug | Easy | Spark plug |
| Blocked Fuel Filter/Line | Replace filter or line | Easy | Fuel filter, fuel line |
| Choke/Throttle Issue | Adjust linkage or lubricate | Easy | Lubricant, tools |
| Vacuum/Gasket Leak | Replace gasket, seal leak | Medium | Gasket, carb cleaner |
Frequently Asked Questions
Why does my lawn mower run for a few seconds and then die?
Usually this means a carburetor blockage, dirty air filter, or old gas. The engine runs on primed fuel but dies as soon as it runs out of usable supply.
How often should I replace my air filter and spark plug?
At least once per mowing season for each, or more often if you mow a lot or in dusty conditions.
Do I need to use fuel stabilizer?
Yes, if you store fuel or your mower for more than 30 days—stabilizer keeps gas fresh and prevents carburetor gumming.
Should I remove and rebuild the carburetor myself?
If you’re handy with basic tools, a rebuild is doable. If not, cleaning with spray may help, or you can have a shop handle a full rebuild affordably.
What if none of these steps work?
If your mower still starts then dies after these fixes, there may be a deeper engine, compression, or electrical issue—time to call a professional.
Conclusion
A mower that starts but won’t stay on is nearly always fixable with some simple cleaning and regular maintenance. Focus on fresh gas, clean air and fuel filters, a healthy spark plug, and a well-kept carburetor for smooth, reliable mowing all season long.