Why does my lawn mower start and then die shortly after?

**Fuel Quality**: Gasoline degrades over time, particularly if left in the mower for months.

Old fuel can lead to stale gas, which does not ignite properly, causing the mower to start and then die.

**Carburetor Issues**: The carburetor mixes air and fuel for optimal combustion.

If it’s dirty or clogged with residue, it can restrict fuel flow, leading to starting issues.

Cleaning the carburetor can often resolve this problem.

**Spark Plug Condition**: A worn or fouled spark plug can produce weak or no sparks.

This results in intermittent or complete combustion failure, causing the engine to die shortly after starting.

Regular inspection and replacement can prevent this issue.

**Fuel Filter Blockage**: Just like the carburetor, the fuel filter can become clogged over time.

This impedes fuel flow into the engine and can cause it to run inconsistently or stall altogether.

**Air Filter Restrictions**: A dirty air filter reduces airflow to the engine.

Since combustion requires both air and fuel, inadequate air supply can make the engine run poorly or die unexpectedly.

**Oil Level**: Low oil levels can trigger safety switches in many mowers that protect the engine from low lubrication.

If the oil level is low, the mower may start but die quickly as a precaution.

**Choke Position**: The choke controls the air/fuel mixture for cold starts.

If the choke is left in the ‘on’ position when the engine warms up, it can cause it to stall as it receives too rich a mixture.

**Clogged Fuel Line**: Blockages in the fuel line can prevent fuel from reaching the carburetor.

These can be caused by debris in the tank, old fuel, or deposits from fuel oxidation.

**Electrical Connections**: Damaged or corroded electrical connections can interrupt the flow of electricity to critical components like the ignition system.

If the connection fails intermittently, the engine can stall.

**Vapor Lock**: This can occur in hot weather.

Fuel in the lines vaporizes before reaching the carburetor, disrupting the fuel supply and causing the mower to stop running, especially if the engine is under load.

**Throttle Issues**: An improperly adjusted throttle can cause erratic engine speed and lead to stalling.

Throttle cables may stretch or bind, affecting the mower's performance.

**Safety Features**: Many modern mowers are equipped with safety features that kill the engine if certain conditions aren’t met, such as the blade being engaged while the operator is not in place or the mower being in an upright position.

Regular inspection and maintenance can prevent this.

**Fuel Cap Vent**: If the vent on the fuel cap is blocked, it can create a vacuum and restrict fuel flow.

This can cause the mower to start, run a bit, and then stall.

**Dirty Cooling Fins**: Overheating due to obstructed cooling fins can cause the engine temperature to rise excessively.

As a result, the engine may shut down as a safety measure.

**Fuel Injector Problems**: On more advanced mowers, clogged fuel injectors can impede fuel delivery.

Like carburetor issues, this can lead to poor performance and unexpected shutdowns.

**Temperature Sensors**: Some engine systems are equipped with temperature sensors that can shut down the engine if it detects overheating, even if the cause isn’t readily apparent.

**Fuel System Orientation**: For some riding mowers, the orientation of the fuel tank and positioning of fuel lines can impact fuel gravity flow.

If seated incorrectly, it may affect the fuel delivery under load.

**Compression Issues**: If the engine has a compression problem, it may start but not run properly.

This can be due to worn piston rings or cylinder wear that affects the engine's ability to maintain combustion.

**Advanced Engine Management Systems**: Some mowers now integrate sensors and electronic control units that monitor engine parameters.

If they detect anomalies outside normal operating ranges, they can kill the engine to prevent damage.