How to Troubleshoot the Starting System on a John Deere Lawn Tractor

Ensure there is fuel in your John Deere riding lawn tractor before proceeding. Insufficient gasoline may simply have been the culprit behind the machine's failure to start.

Open the front hood of the John Deere riding lawn tractor. Ensure the black plug wire at the front of the engine assembly is securely plugged into the spark plug. If it is not, immediately reinsert it and attempt to crank the tractor's engine.

Replace the spark plug if the lawn tractor still will not crank. Disconnect the John Deere's plug wire from the current spark plug and reconnect it to a new spark plug.

Find the John Deere riding lawn tractor's air gap if the tractor still will not start. Use the plug wire attached to the spark plug as a guide. Follow the plug wire to the rear of the John Deere's assembly, where it leads to the circular magnetic coil. The engine's flywheel is directly behind the magnetic coil, and the slight space created between the two is the air gap. Measure the gap and ensure it is between the 0.010 and 0.015 of an inch, which is roughly the thickness of a business card.

Free up the magnetic coil by loosening it with a wrench. Incrementally reposition the coil so the air gap between it and the flywheel is between 0.010 and 0.015.

Close the John Deere riding lawn tractor's hood.