Why Won't My Lawn Mower Start? 7 Common Causes

Nothing is more frustrating than pulling the cord on your mower and getting nothing. Before you panic, most no-start issues have simple causes. Here are the seven most common reasons your lawn mower won't start.

1. Old or Bad Fuel — This is the number one cause. If fuel has been sitting in the tank for more than 30 days, it may have degraded. Drain the old fuel and refill with fresh gas. If the fuel smells like varnish instead of gasoline, the carburetor likely needs cleaning too.

2. Dirty or Fouled Spark Plug — Pull the spark plug and inspect it. If it's black and sooty, wet with fuel, or the electrode is worn, replace it. While you have it out, check for spark by grounding the plug against the engine and pulling the cord — you should see a blue spark.

3. Clogged Air Filter — A severely clogged air filter can prevent the engine from getting enough air to start. Remove it and try starting without it. If the engine starts, you found the problem. Replace the filter before mowing.

4. Stale Fuel in the Carburetor — Even if you add fresh fuel to the tank, old fuel may still be sitting in the carburetor bowl. The carburetor needs to be cleaned or at minimum, drained. Some carburetors have a drain bolt on the bottom of the bowl.

5. Safety Switch Issues — Most modern mowers have safety switches that prevent starting unless certain conditions are met. Push mowers have a bail lever (the handle you squeeze). Riding mowers have a seat switch, blade engagement switch, and brake/clutch switch. Make sure all safety mechanisms are properly engaged.

6. Low or No Oil — Many newer engines have a low-oil shutoff switch that prevents starting when oil is low. Check the dipstick and add oil if needed.

7. Dead Battery (Riding Mowers) — If your riding mower clicks but won't turn over, the battery is likely dead. Try jump-starting it or charging the battery. If the battery won't hold a charge, it needs replacement.

If you've checked all seven of these and your mower still won't start, it's time to bring it in. We diagnose starting problems every day and can usually pinpoint the issue quickly.