March 1, 2016

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

By Lyle Weischwill
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 replacement 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
Tools required
Nut driver set
Feeler gauge set
Work gloves
Repair difficulty
Time required
30 minutes or less
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.

Disconnect the spark plug.

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.

Remove the blower housing.

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.

Remove the ignition coil screws.

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.
Set the ignition coil air gap.

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.
Symptoms for gas walk-behind mowers

Choose a symptom to see related walk-behind mower repairs.

Main causes: drive control cable failure, worn or broken drive belt, bad transmission, broken drive wheel
Main causes: damaged cutting blade, loose cutting blade, damaged flywheel key, engine needs tune up
Main causes: dirty carburetor, bad spark plug, clogged air filter, engine choke problems, clogged gas cap vent
Main causes: stale gas, engine needs tune up, bad spark plug, dead battery, bad recoil starter, faulty safety switch, bad ignition coil
Main causes: engine needs tune up, dirty or clogged carburetor, damaged flywheel key
Main causes: uneven wheel height settings, damaged wheel, dull or damaged cutting blade
Repair guides for gas walk-behind mowers

These step-by-step repair guides will help you safely fix what’s broken on your walk-behind lawn mower.

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

Replace the ignition coil if it isn't sending electric current to the spark plug when you pull the recoil starter rope.

Repair difficulty
Time required
 30 minutes or less
How to replace a lawn mower flywheel key on an OHV engine

The flywheel key couples the flywheel to the engine crankshaft. Replace the flywheel key if it's broken.

Repair difficulty
Time required
 60 minutes or less
March 1, 2016
By Lyle Weischwill
How to replace a lawn mower drive cable

The drive cable engages the transmission to spin the drive wheels and move the mower across the grass. Replace the drive cable if it's broken or frozen up inside the sheath.

Repair difficulty
Time required
 60 minutes or less
Articles and videos for gas walk-behind mowers

Use the advice and tips in these articles and videos to get the most out of your walk-behind lawn mower.

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