Lawn Mower Won't Start
A lawn mower that won't start is usually a fuel problem. In 80% of cases, draining old gas and adding fresh fuel fixes it. If that doesn't work, check the spark plug and air filter next. Most issues take under 30 minutes to diagnose and fix.
Quick Diagnostic Checklist
- 1. Check fuel freshness — Gas older than 30 days can cause starting problems. Drain and refill with fresh fuel.
- 2. Inspect spark plug — Remove it and look for fouling, corrosion or wet deposits. Replace if worn or damaged.
- 3. Check air filter — A clogged filter restricts airflow. Clean or replace if dirty.
- 4. Verify safety switches — Blade bail, seat switch (riding), kill switch must all be properly engaged.
- 5. Test for spark — Ground the plug against the engine and pull the cord. No spark = ignition problem.
⛽ Fuel-Related Causes
Bad fuel is the #1 reason mowers won't start. Ethanol in modern gas attracts moisture and degrades quickly.
Frequently Asked Questions
Why won't my lawn mower start?
The most common reasons are: stale fuel (80% of cases), dirty air filter, fouled spark plug, or carburetor issues. Start by checking if the fuel is fresh (less than 30 days old) and the spark plug has a good spark.
How do I fix a lawn mower that won't start after sitting?
Drain the old fuel completely, replace with fresh gas, check/clean the carburetor (may need carb cleaner spray), replace the spark plug, and clean or replace the air filter. Most mowers start after addressing fuel issues.
What causes a lawn mower to turn over but not start?
If the engine cranks but won't fire, you likely have a fuel delivery or spark issue. Check: fuel valve is on, fuel is reaching the carburetor, spark plug is firing, and the kill switch isn't engaged.