March 01, 2016

How to replace a lawn mower ignition coil on an OHV engine

This lawn mower repair guide has step-by-step instructions for how to replace the ignition coil on a lawn mower with an overhead valve (OHV) engine. The ignition coil sends current to the spark plug to ignite the fuel in the cylinder. A failed ignition coil is one reason a lawn mower won’t start. You can determine if the ignition coil is the problem by following the troubleshooting steps in Lawn Mower Won't Start Troubleshooting Video: Spark and Ignition Problems.

If the ignition coil doesn't send electric current to the spark plug when you pull the starter rope, replace the coil with the manufacturer-approved lawn mower part.

This repair guide and video shows how the replace the ignition coil on common Briggs & Stratton OHV engines that power Craftsman, Husqvarna, Poulan, Troybilt, MTD, Toro, Cub Cadet and Ariens walk-behind lawn mowers.

If your lawn mower is an older model with a flathead engine, see How to Replace a Lawn Mower Ignition Coil on a Flathead Engine.

Quick links

Video

Instructions

Tools required

Nut driver set

Feeler gauge set

Work gloves

Repair difficulty

Time required

30 minutes or less

Replacing an ignition coil on a lawn mower OHV engine

This video explains how to replace the ignition coil on a walk-behind lawn mower with an OHV engine.

Instructions

01.
Disconnect the spark plug wire
Disconnect the spark plug wire from the spark plug.
PHOTO: Disconnect the spark plug.
02.
Remove the blower housing
Release the starter rope from the mower handle.
Remove the screws from the blower housing.
Pull the blower housing off the engine.
PHOTO: Remove the blower housing.
03.
Remove the ignition coil
Rotate the flywheel to position the flywheel magnets away from the ignition coil.
Disconnect the stop wire.
Remove the ignition coil mounting screws.
Pull the ignition coil off the engine.
PHOTO: Remove the ignition coil screws.
04.
Install the new ignition coil
Position the new ignition coil on the mounting posts and line up the mounting screw holes.
Loosely reinstall the ignition coil mounting screws.
Pull the ignition coil as far away from the flywheel as possible then tighten the mounting screws.
Insert the 0.010-inch feeler gauge leaf between the coil arms and the flywheel.
Rotate the flywheel to position the flywheel magnets in front of the ignition coil.
Loosen the ignition coil mounting screws and allow the magnets to pull the ignition coil against the feeler gauge leaf.
Tighten the mounting screws and work the feeler gauge leaf out of the ignition coil air gap.
Connect the stop wire to the new ignition coil.
Tip: Use a business card instead of a feeler gauge leaf to set the ignition coil air gap—it’s about the same width.
PHOTO: Set the ignition coil air gap.
05.
Reinstall the blower housing
Position the blower housing on the top of the engine and line up the mounting holes.
Reinstall the mounting screws.
Reconnect the starter rope to the mower handle.
06.
Reconnect the spark plug wire
Connect the spark plug wire to the spark plug.

Warning: Undertaking repairs to appliances can be hazardous. Use the proper tools and safety equipment noted in the guide and follow all instructions. Do not proceed until you are confident that you understand all of the steps and are capable of completing the repair. Some repairs should only be performed by a qualified technician.