Why Won't My Lawn Mower Start?


Lawn mowers are an invaluable tools for making your yard look well maintained. However, nearly all of us have felt the frustration when a mower will not start at the beginning of season, or when the grass is knee deep due to procrastination. There are many reasons why a mower engine will not start properly.


Engines need to be filled with gas an oil to run properly. Without gas, the engine will not be able to start, as fuel provides the combustion necessary to get the parts moving. A lack of oil in the engine will cause components to freeze, causing damage, and in extreme cases, cause the engine to stop working completely. Fuel that has sat in the engine for an extended period will go stale, causing blockage in the engine due to settled debris and may contain excess water.

Air Filter

The air filter purifies the air that moves over the engine while running. If the air filter is clogged or dirty, it may cause the engine to lose power and potentially not start at all. Air filters can be removed from the lawn mower and checked for excessive amounts of dirt and debris. If the air filter is made from paper, it should be replaced completely, while foam filters can be cleaned with water and dish washing detergent, then dried.

Spark Plug

Spark plugs provide the spark that ignites the fuel in the engine, making the mower run. If the spark plug is dirty or faulty, it will not be able to provide the spark necessary for the engine to run. Cleaning the spark plug of oil and moisture may solve the problem. The spark plug needs to be set so that the gap at its bottom, the portion that is put into the engine, is set to the correct length. The mower manual will give specifics on how big the gap should be. The gap size can be checked using a spark plug gapping tool, available from most hardware stores.

Safety bar

Many lawn mowers have safety triggers that need to be tripped before the lawn mower will start. On a riding lawn mower, these safety trips are usually under the seat. Unless there is weight on the seat, the mower will not start. On a push mower, there may be a bar towards the handle that needs to be held down before the mower will start. If the safety catches are not engaging properly, the mower will not start. Wires that connect these safety measures to the engine should be checked for damage and that they are connected properly.


If the spark plug is working, the carburetor might be the problem. The carburetor is the part of the engine that mixes fuel and air together to propel the machine. The carburetor will sometimes have a fuel shut off valve that can become closed or clogged by debris, causing the carburetor to not get enough fuel. If the engine runs for a few moments and then quits, the carburetor may need to be serviced by a technician.

Keywords: lawn mower, mower troubleshooting, mower engine issues

About this Author

Cleveland Van Cecil is a freelancer writer specializing in technology. He has been a freelance writer for three years and has published extensively on eHow.com, writing articles on subjects as diverse as boat motors and hydroponic gardening. Van Cecil has a Bachelor of Arts in liberal arts from Baldwin-Wallace College.