Lawn mowers are built around relatively simple engines that get the job done with little fuss. Keeping up with the maintenance schedule of a lawnmower, as well as regular cleaning and TLC, will usually keep a mower running for years. But the engine can have problems, no matter how well you take care of it. Not all problems are major, and knowing how to troubleshoot the small things can prevent major issues later on.
Check to make sure the engine has enough fuel and oil by checking their respective wells in the engine. If the fuel looks low, fill it up. Check the oil level against the dip stick.
Check that the starter cord is working properly. If the cord does not go in or out properly, check that the spring inside the starting unit is not bent or loose.
Check that the safety catches are engaging properly. A safety handle that controls the engine starting may fail. Check the wire that goes from the safety handle to the engine to ensure it is properly attached.
Check the spark plug to see if it is wet or black. Replace it if it shows either sign.
Check the air filter if the engine starts but performs improperly, such as stuttering or cutting out. Clean or replace the air filter if it looks dirty.
Check the battery of the lawn mower, if it has one, to see whether it is attached and that it has a charge.
Look under the mower to see if it is clogged with grass. This may cause the mower to fail when it starts. Clean underneath the lawn mower using a putty knife to remove excess grass. Remove the spark plug before working under the mower to prevent injury.