Riding Mower and Tractor: Won't start

There are numerous explanations for why a riding lawn mower won’t start, including everything from bad gas or a bad battery to a failed starter motor or bad ignition coil.

If you find yourself constantly having to charge the battery before starting the engine, a bad battery or failed alternator could be causing the problem. Connect the battery to a charger and if the battery won’t charge fully within 8 hours, then you’ll likely need to replace the battery. If the battery is okay, then a problem in the engine’s charging system is causing the constantly drained battery. The engine uses an alternator to generate current, which constantly charges the battery and powers the mower’s electrical system while the engine runs. When the alternator fails, the battery attempts to power the mower on its own and quickly drains without recharging.

If the engine spins but won’t start when you turn the ignition key, the engine is missing one of its key ingredients for starting—fuel, compression or spark. Check your basics first, then watch this video for troubleshooting tips to get the engine started: Riding Lawn Mower Engine Spins But Won't Start.

You may hear a click when you turn the ignition key but nothing else. A dead battery, bad starter solenoid, failed starter motor or a seized engine could be the cause. Our video, Riding Lawn Mower Engine Clicks But Doesn't Turn Over, will help you figure out what to fix.

When the mower seems completely dead, you’ll need to check the battery, ignition switch, interlock switches, starter solenoid and wiring to find out what’s wrong. This video will help you systematically check those parts: Riding Lawn Mower Engine Won’t Turn Over or Click.

Once you determine a cause, use one of the repair guides below to fix your riding mower.

These repairs may help solve your Riding Mower and Tractor problem:

Replace the riding mower ignition switch

Ignition switch

The ignition switch in a lawn tractor or riding mower supplies power to the electrical components of the engine. If the lawn tractor doesn't turn over when you turn the key to the On position or doesn't shut off when you turn the key to the Off position, you might need to replace the ignition switch.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the riding mower ignition coil

Ignition coil

The ignition coil in a riding mower or lawn tractor produces the energy to cause the spark at the spark plug. The ignition coil is the likely the cause when the engine won't spark if, after you remove the kill wire, there's no spark from a known good spark plug.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the riding mower carburetor assembly

Carburetor

If the engine on your riding mower or lawn tractor is running roughly or only runs when the choke is partly on, you might need to replace the carburetor. The carburetor mixes gas with air before the fuel goes into the cylinder. If the gas/air mix isn't balanced, the engine won't have peak performance.

For manuals, repair guides, and specific part recommendations, enter your model number.

Rebuild the riding mower engine carburetor

Carburetor rebuild kit

The carburetor mixes fuel with air to create a combustible mixture that enters the engine cylinder and ignites to drive the piston. Impurities in gasoline can clog the carburetor. Seals and gaskets in the carburetor eventually wear out. Use a carburetor rebuild kit to refurbish a clogged or leaking carburetor.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the riding mower battery

Battery

If the riding mower or lawn tractor engine doesn't make any noise when you try to start the mower, it might be time to replace the lawn tractor battery. A good indicator that the lawn tractor needs a new battery is if you charge the battery, and it loses the charge quickly.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the alternator

Alternator

The alternator attaches to the engine under the flywheel and generates power for the tractor while the engine is running. The alternator also recharges the battery while the engine runs. If the battery drains while running the tractor, the alternator could be at fault. Check DC voltage at the battery with the engine running. You should measure between 13 and 14 volts. If not, then you may need to replace the alternator.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the starter solenoid

Starter Solenoid

The starter solenoid is a coil-activated switch that activates the starter motor. When you turn the ignition switch to the start position, the ignition switch triggers the coil inside the solenoid body to raise a high-voltage contact plate that bridges the terminal posts on top of the solenoid body. High current flows from the positive battery cable connected to one post, through the contact plate, to the starter cable connected to the other post, causing the starter motor to spin. The starter solenoid clicks when the activated coil raises the contact plate. Replace the starter solenoid if it doesn't click when you turn the key.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the air filter

Air filter

The air filter traps debris from carburetor inlet air. A dirty air filter could be the problem if the engine stalls after starting or the engine runs rough or sputters. The carburetor won't get enough air to mix with the fuel for combustion if the air filter is dirty. Inspect the air filter regularly and replace it when dirty.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the starter motor

Starter Motor

The starter motor spins the flywheel to start the engine when you turn the ignition key to the start position. If the starter motor runs but doesn't spin the flywheel, check the starter motor's drive gear for damage. A defective drive gear won't mesh with the flywheel teeth to spin the engine. Replace the starter motor if you find damage to the drive gear. The starter motor may be defective if it doesn't run when activated. Other failures such as a locked up engine or poor current flow to the motor can prevent the starter from spinning, so check those issues first. Replace the starter motor if it won’t run and you've eliminated other possible failures that could prevent the starter motor from running.

For manuals, repair guides, and specific part recommendations, enter your model number.

Replace the brake interlock switch

Brake Interlock Switch

The brake interlock switch detects whether you have the brake pedal fully pushed down. The parking brake holds the brake pedal in the fully depressed position so the brake interlock switch also recognizes whether you have the parking brake set. The brake interlock switch prevents you from starting the tractor without the brake pushed in or the parking brake set. Replace the brake interlock switch if the engine won't start because the brake interlock switch doesn't detect the brake pedal fully depressed or the parking brake set.

For manuals, repair guides, and specific part recommendations, enter your model number.