How to Install an Ignition Coil on a Lawnmower

Pull the black rubber boot off the end of the spark plug. The spark plug is usually located on the front or side of the engine block. Even with a failing coil, there is a chance that you could inadvertently start the engine while you’re working on it – causing serious injury. Disconnecting the spark plug eliminates the possibility of an accidental start.

Remove the screws from the plastic cowling covering the top of the engine with a Phillips-head screwdriver. On some lawnmowers, it may be necessary to drain and disconnect the fuel tank to remove the cowling. For most engines, however, you can simply remove the screws from the cowling, lift it off the engine and turn it to the side, leaving the fuel lines attached.

Remove the bolts from the rewind housing with a socket wrench. The rewind housing is the metal cap that sits over the top of the engine. The starter rope comes out of the top of the housing and there are usually some cables screwed to the side of it. Look around the base of the housing for the bolts that hold it to the engine. Usually there are eight bolts; two bolts are located on each side of the housing. Lift the housing off the engine and turn it to the side to get it out of the way.

Look for the ignition coil next to the flywheel. The flywheel is the round plate with vertical fins sticking out of it that sits atop the engine. Follow the spark plug wire up to the flywheel. The module that the spark plug wire attaches to is the ignition coil. Two magnets are embedded in one side of the flywheel. You can locate them by touching the tip of a screwdriver to the flywheel. When the screwdriver sticks, you’ve found the magnets. Turn the flywheel so the magnets are opposite the ignition coil.

Pull the thin wire off the terminal on the side of the ignition coil. The wire connects to the engine block, providing a ground for the ignition coil. This ground acts as a “kill switch” – directing the electric current away from the spark plug when you turn off the engine. Grip the terminal connector with needle-nose pliers and pull it off the terminal.

Remove the two bolts from the top of the ignition coil with a socket wrench. Pull the ignition coil off the engine.

Place a new coil on top of the engine. Insert the two bolts in the top of the coil. Hold the spacers that came with the coil between the coil and the flywheel. Turn the flywheel until the magnets pull the ignition coil against the spacers. Tighten the bolts securely to hold the ignition coil in place. If your ignition coil didn’t come with spacers, you can place a business or index card between the coil and the flywheel. Remove the spacer or card and turn the flywheel. The flywheel should spin freely, without touching or rubbing the coil.

Connect the thin wire to the terminal on the ignition coil.

Place the rewind housing on the mower and secure it with the bolts. Place the cowling on the engine; insert and tighten the Phillips-head screws to secure it. Slide the spark plug boot over the end of the spark plug and push it firmly into place.