There’s nothing more frustrating than pulling the cord (or turning the key) and getting nothing but silence from your lawn mower. Before you call for repairs or give up, follow this straightforward troubleshooting guide. Most “no start” problems have simple solutions you can handle at home with basic tools and a little know-how.
Quick Picks: What to Check First When a Lawn Mower Won’t Start
- Is there fresh gasoline in the tank?
- Is the spark plug clean and connected?
- Is the air filter clean and in place?
- Is the oil at the proper level?
- Are all safety switches and levers engaged?
- Is the battery charged (if electric start)?
- Are the fuel and ignition systems in good shape?
Buyer’s Guide: Tools & Supplies You’ll Need
- Socket set and wrenches: For spark plug and battery access.
- Phillips and flathead screwdrivers: For air filter and panel removal.
- Carburetor cleaner spray: For cleaning fuel passages.
- Replacement spark plug and air filter: For quick tune-ups.
- Battery charger or replacement battery: For electric start mowers.
- Fresh gasoline: Never use old or stale fuel.
- Wire brush: For cleaning spark plugs and battery terminals.
- Owner’s manual: For reference and part locations.
Step-by-Step Troubleshooting: Why Your Lawn Mower Won’t Start
1. Check the Fuel System
- Make sure there’s fresh gasoline in the tank. Gas older than 30 days can prevent starting.
- If old gas is present, drain the tank and carburetor bowl, then refill with fresh fuel.
- Prime the engine as directed in your manual, if applicable.
2. Inspect the Spark Plug
- Remove the spark plug with a socket wrench. Check for carbon buildup, oil, or damage.
- Clean the electrode with a wire brush or replace the plug if it’s worn or blackened.
- Reconnect the plug wire tightly after installation.
3. Examine the Air Filter
- Remove the filter cover and inspect the air filter for dirt, oil, or clogging.
- Clean foam filters with soap and water or replace paper filters if dirty.
- A clean air filter ensures proper airflow and easier starting.
4. Test the Battery (if electric start)
- Check voltage with a multimeter—should read 12.4–12.8V for 12V systems.
- Charge the battery if low, or replace it if it won’t hold a charge.
- Clean battery terminals and connections with a wire brush.
5. Check Oil Level and Quality
- Remove the dipstick and verify oil is at the proper level and clean.
- Low or dirty oil can trigger a no-start shutoff on many newer mowers.
- Add or change oil as needed before trying to restart.
6. Inspect Safety Switches and Controls
- Ensure all safety levers, handles, and seat switches are properly engaged.
- On riding mowers, check the brake pedal and PTO/blade switch positions.
- Replace any switches that seem loose or broken.
7. Clean the Carburetor
- Remove the air filter and spray carburetor cleaner into the intake.
- If possible, remove and clean the carburetor jets or passages if you suspect old fuel residue.
- Reinstall and attempt to start the engine again.
8. Inspect Fuel Lines and Filter
- Check for cracks, blockages, or kinks in the fuel line.
- Replace the in-line fuel filter if it appears dirty or discolored.
- Ensure fuel flows freely from the tank to the carburetor.
9. Look for Engine Flooding
- If you smell gas or see a wet spark plug, let the mower sit for 15–30 minutes before restarting with the choke off and throttle open.
Comparison Table: Lawn Mower Starting Problems & Solutions
| Problem | Solution | Difficulty | Parts Needed |
|---|---|---|---|
| Old/Stale Gas | Drain and refill tank | Easy | Fresh gasoline |
| Dirty Spark Plug | Clean or replace plug | Easy | Spark plug |
| Clogged Air Filter | Replace or clean filter | Easy | Air filter |
| Dead Battery | Charge or replace battery | Easy | Battery, charger |
| Low/Dirty Oil | Add/change oil | Easy | Oil |
| Faulty Safety Switch | Repair or replace switch | Easy | Switch, wiring |
| Carburetor Problems | Clean or rebuild carb | Easy-Medium | Carb cleaner, gaskets |
| Blocked Fuel Line/Filter | Replace filter/clean line | Easy | Fuel filter/line |
| Flooded Engine | Wait, start with choke off | Easy | — |
Frequently Asked Questions
How do I know if my mower is flooded?
If you smell raw gas or see a wet spark plug, your engine may be flooded. Let it sit, then restart with choke off.
What’s the most common cause of starting problems?
Old fuel, dirty carburetor, and fouled spark plugs are the biggest culprits—especially after winter storage.
How often should I change my air filter and spark plug?
At least once per season, or more often if mowing in dusty conditions or heavy use.
When should I call a pro?
If you’ve checked every step here and your mower still won’t start, a small engine mechanic can check for deeper engine or electrical problems.
Conclusion
Most lawn mower starting problems are caused by simple issues—bad gas, a dirty plug, or clogged filter. A quick inspection and tune-up will solve most no-start headaches, so you can get back to enjoying a neat, beautiful lawn!