To change the coil in a lawn mower, locate the ignition coil under the vehicle's hood, disconnect the wires of the coil and the spark plug, and detach the coil from the mower's motor. Replace with the new ignition coil, place the bolts loosely, and reconnect the coil's and spark plug's wires. Test for proper coil installation using a business card, and close the vehicle's hood.
To locate the ignition coil of the lawn mower, open the hood of the mower, or take out its engine cover. Locate the mower's spark plug, and disconnect the wire connected to it. This wire should run to the mower's ignition coil positioned beneath the flywheel of the motor.
Use a pair of needle-nosed pliers to disconnect the small wire connected to the coil. With a socket wrench or screwdriver, remove the bolts that secure the coil to the motor, and tug the coil away and off the motor.
Position the new ignition coil, and bolt it loosely. After connecting the respective wires to the new coil and the spark plug, slip in a business card in the space between the two components. Tighten the bolts of the coil, and manually turn the motor's flywheel. The card should spin along with the flywheel.
If the card does not allow the flywheel to spin freely, undo the bolts of the coil, reposition it, and repeat the business card test to check for proper installation. Finally, close the hood of the mower or replace its engine cover.