It’s a frustrating scenario: you pull the cord, your lawn mower sputters to life—then dies seconds later. Or maybe it runs for a minute, sputters, and stalls. If your lawn mower starts but won’t stay on, you’re not alone. This common problem has clear, fixable causes—most of which you can handle at home with basic tools and a little time. Below, you’ll find the most common reasons, how to diagnose them, and step-by-step instructions to get your mower running smoothly from start to finish.
Quick Picks: Why Does My Lawn Mower Start and Then Stall?
- Dirty Carburetor: Gummed-up fuel from sitting can block jets, so your mower only runs on the primer shot, then dies.
- Clogged Air Filter: A dirty or soaked filter suffocates the engine, causing it to stall.
- Old or Bad Gas: Gasoline that’s more than a month or two old can cause erratic running and stalling.
- Faulty Spark Plug: A fouled or worn plug can create weak, unreliable spark.
- Blocked Fuel Line or Fuel Filter: Debris in the tank or line restricts fuel flow after starting.
- Faulty Ignition Coil: Rare, but if the coil gets hot and cuts out, the mower stalls.
- Stuck Choke: If the choke stays closed after starting, the engine floods and dies.
Buyer’s Guide: Tools & Supplies You’ll Need
- Socket wrench set: For spark plug removal and carburetor access.
- Carburetor cleaner spray: Dissolves varnish and old fuel deposits.
- Replacement air filter: Foam or paper, matched to your model.
- New spark plug: Always use the recommended type.
- Fuel line/fuel filter: For replacement if blockage is found.
- Fresh gasoline: Never use last season’s gas.
- Basic hand tools: Screwdrivers, pliers, gloves.
Step-by-Step Guide: How to Fix a Lawn Mower That Starts Then Dies
1. Replace Old or Bad Gasoline
- Drain the tank completely (use a siphon or tilt the mower with the air filter up).
- Refill with fresh, clean gasoline—no older than 30 days.
- Add a fuel stabilizer if you mow infrequently or store the mower between uses.
2. Clean or Replace the Air Filter
- Remove the air filter cover and take out the filter.
- If it’s dirty, soaked with oil, or falling apart, replace it with a new one.
- A clogged filter restricts air and causes stalling.
3. Inspect and Clean the Carburetor
- Remove the air filter and spray carburetor cleaner directly into the carb intake.
- Let it sit for 5–10 minutes, then try to start the engine.
- If the mower starts and dies again, deeper cleaning may be needed: remove the carburetor bowl and jets, clean with carb spray, and reassemble.
- If you’re not comfortable disassembling, a repair shop can deep-clean or rebuild the carb.
4. Check and Replace the Spark Plug
- Remove the spark plug with a socket and inspect for carbon buildup, oil, or damage.
- Clean with a wire brush or replace with a new, properly gapped plug.
- A weak spark causes poor combustion and stalling.
5. Inspect the Fuel Line and Fuel Filter
- Look for cracks, blockages, or pinched areas in the fuel line.
- Remove and blow out or replace the fuel filter if equipped.
- Any obstruction can limit fuel flow, causing the engine to die after using up the primer fuel.
6. Verify Choke and Throttle Operation
- Check that the choke opens fully after starting. If stuck closed, free it and lubricate as needed.
- Make sure throttle and choke linkages move smoothly and aren’t binding.
7. (For Riding Mowers) Test the Ignition Coil
- If the mower starts cold, runs for a minute, then stalls and won’t restart until it’s cool, the ignition coil may be failing.
- Test with a spark tester or replace if suspected.
Comparison Table: Lawn Mower Stalls After Starting – Causes & Fixes
| Problem | Solution | Difficulty | Parts Needed |
|---|---|---|---|
| Dirty Carburetor | Clean or rebuild carburetor | Medium | Carb cleaner, gaskets |
| Clogged Air Filter | Replace filter | Easy | New air filter |
| Old/Bad Gas | Drain and refill with fresh gas | Easy | New gasoline |
| Bad Spark Plug | Clean or replace plug | Easy | Spark plug |
| Blocked Fuel Line | Clear or replace line/filter | Easy-Medium | Fuel line, filter |
| Stuck Choke | Free and lubricate choke | Easy | Spray lubricant |
| Faulty Ignition Coil | Replace coil | Medium | Ignition coil |
Frequently Asked Questions
Why does my mower die after running for a few seconds?
This usually means a carburetor blockage, clogged fuel filter, or old gas. The engine burns the fuel primed into the carb, then dies when the flow stops.
Should I use carburetor cleaner even if I’m not removing the carb?
Yes. Spraying carb cleaner into the intake is a good first step, but a full cleaning may be required if stalling continues.
Is it safe to run a mower without an air filter?
No. Running without a filter allows dirt and debris into the engine, causing wear and damage.
How do I keep this from happening again?
- Always use fresh gasoline—never store gas for more than a month.
- Replace the air filter and spark plug every season.
- Use a fuel stabilizer if storing your mower for more than 30 days.
- Run the mower dry or drain fuel before winter storage.
When should I call a professional?
If you’ve tried all these steps and the mower still won’t run, or if you’re not comfortable with carburetor cleaning, a small engine mechanic can help.
Conclusion
If your lawn mower starts but won’t stay running, don’t give up! The most common causes—bad gas, dirty carburetor, clogged filter, or spark issues—are all fixable at home. Follow this guide to get your mower running strong, and make regular maintenance a habit for hassle-free mowing all season long.