How to Check Ignition Systems on Lawn Mowers

The ignition system on a lawn mower contains the spark plug, the HT lead wire and the module--everything necessary for combustion. For the ignition system to work properly, the flywheel needs to spin around the crankshaft fast enough to generate enough magnetic energy to fire the high voltage charge building in the coil. These ignition systems contain a potentially lethal amount of voltage. Always wear safety equipment and follow all safety procedures when working on a lawn mower ignition system.

Socket wrench
Spark plug socket
Test plug
Leather work gloves
Screwdriver

Instructions

- 1
  Slip the rubber boot off the end of the of the spark plug, wiggling it back and forth lightly, if necessary. Check the metal prong inside the boot and the boot's connection to the HT wire to see if it's bent, covered in dirt or broken in any way.
- 2
  Unscrew the spark plug from the cylinder hole. Hook the test plug up to the boot on the end of the HT wire. Attach the test plug to a grounded metal point on the engine block. Turn on the ignition switch, if your lawn mower uses one.
- 3
  Pull on the starter rope and look for a blue spark to jump across the metal points. If the blue spark is present, the ignition system is fine. If the spark is absent or a weak yellow, inspect the HT wire and short-circuit wire as they lead back to the ignition module.
- 4
  Replace any damaged, pinched or frayed electrical wires. Repeat test for a spark. Replace the ignition module if there's still no spark. Use the screwdriver to touch a metal point on the ignition module to ground it before pulling off any wires.

How to Check a Lawn Mower's Starter

Brown Vs. Black Mulch

Garden Tools & Supplies