John Deere has made many different models of walk-behind lawn mowers over the years. There has only been two engines ever used on John Deere walk behinds, Kawasaki and Briggs and Stratton. If your lawn mower fails to start there are numerous steps to take to find the issue. These steps are used for both the Kawasaki and Briggs and Stratton engines.
Place mower on level ground. Check the engine oil. The oil dip stick is located on top of the engine and has a twist top. If the oil level is low as indicated on the markings on the dipstick, add oil until the dipstick reads "FULL."
Pull the starting cord located on top of the engine to ensure the engine is turning over. On top of the right side of the engine is the air filter cover. It has a hand-tighten screw on top of it. Unscrew and remove the air filter. Clean or replace the the air filter.
Leave the air filter out. Looking over the top of the air filter casing, you can see the inside of the carburetor. Spray a small amount of carburetor cleaner into the inside of the carburetor. Pull the starting cord. If it starts, then immediately shuts down, the carburetor is defective and needs replacing. If the lawn mower doesn't start, reinstall the air filter and air filter cover.
Remove the spark plug with either the 5/8-inch or 7/8-inch socket, depending on the model. The spark plug its located on the front of the engine with a wire plugged into it.
Clip the spark plug tester into the spark plug wire. Clip the other end of the tester to a metal piece on the engine block. Pull the starting cord while watching the tester to see if there's spark.
Change the spark plug if the tester is showing spark. If the tester shows no spark, replace the ignition coil.
Replace the flywheel key if the lawn mower still won't start after installing a new spark plug and the spark tester was positive for spark.