There are many reasons a riding lawn mower won’t start—everything from stale gas to ignition switch problems.
We offer this comprehensive troubleshooting guide that covers 3 different scenarios when your riding mower won’t start:
- Nothing happens when you turn the key.
- The starter solenoid clicks when you turn the key but nothing else happens.
- The engine cranks (turns over) but won’t start.
Follow the expert troubleshooting advice for the symptom that you’re encountering and you can likely start the engine and quickly get back to mowing.
Nothing Happens When You Turn the Key
A dead battery or electric system failure can cause this symptom. This DIY riding mower troubleshooting video provides expert advice to help you get your mower started.
Need to have your riding mower serviced by a Sears Technician?Schedule a repair appointment now.
Check Brake and Blade Controls
Before you do anything, make sure the parking brake is set and the blades are disengaged. The riding mower won’t start otherwise. Your riding mower won’t do anything when you turn the key with the brake off or the blades turned on.
Check the Battery
A dead battery won’t power up the starting system and will prevent the solenoid coil from clicking.
To see if the battery is dead, measure voltage across the battery terminals using a multimeter. If it measures less than 12 volts, the battery is weak or dead and you’ve likely found the problem.
Try recharging the battery using a charger. Or, you can use jumper cables to jump-start a riding lawn mower that uses a 12-volt battery. Charge or replace the battery after jump-starting the engine to see if the mower will start.
Test the Alternator
If you constantly have to charge the battery or jump start your mower, a bad battery or failed charging system could be causing the problem. If the battery won’t charge fully within 8 hours when connected to a charger, you probably need to replace the battery. If the battery is okay, blame shifts to the charging system.
On lawn tractors with a Briggs & Stratton engine, you can check to see if the alternator is working by performing this quick and easy DIY test:
- Start the engine (jump start it if you need to).
- Turn the headlights on.
- Shut off the engine and see if the headlights dim.
If the headlights dim after shutting down the engine, then the alternator is okay. It’s supplying charging current to the battery and causing the headlights to be brighter when the engine is running.
If the headlights don’t dim, then a bad alternator, wiring failure or failed diode could be preventing the battery from getting current to recharge when the engine runs. Some riding mowers also have a fuse in the charging system that will prevent the battery from getting recharge current from the alternator.
Have a Sears Technician diagnose and repair the riding mower if the alternator isn’t working.
Check for Power to the Starter Solenoid
If you hear no solenoid click and the engine won’t crank with a charged battery, then check to see if current is making it through the red battery cable to the solenoid post. Touch the red multimeter probe to the red post on the starter solenoid as shown in the video and touch the black meter probe to the negative terminal on the battery. You should measure more than 12 volts.
Warning: Don’t let the meter lead touch both the solenoid posts at the same time or you’ll see a severe spark. Shorting across the solenoid posts sends the current to the starter motor. Some of you may be tempted to short across the solenoid posts intentionally using an insulated screwdriver to start the engine. But we strongly discourage this approach, because this dangerous practice overrides safety switches.
If the meter measures less than 12 volts, check the battery terminals and cable leads for corrosion. Clean corrosion off the battery terminals and battery cable leads with a wire brush—corrosion can prevent the red solenoid post from getting power. Recheck the voltage. If it still doesn’t measure more than 12 volts at the red post, replace the red battery cable.
Check for power to the starter solenoid coil
If the red terminal is getting power, the next step is to find out whether the solenoid coil gets power when you turn the key.
Test power going to the starter solenoid coil when you turn the key as shown in the video.
If you measure voltage at the coil but the internal contact doesn’t click, the starter solenoid is to blame. Replace the starter solenoid if it’s bad.
If your meter measures 0 volts at the solenoid coil, there’s a break in the circuit to the solenoid coil. The starter solenoid is likely okay, it’s just not getting power. Next, you’ll need to test the coil circuit.
How to Test the Starter Solenoid Coil Circuit
Check the ground side of the circuit first. The black wire attaches to the solenoid coil and connects to the metal frame of the riding mower as a ground. A break in that wire keeps the coil from getting power.
To test the ground wire, check for resistance between the female spade on the black wire and the metal frame of the mower.
- A reading near 0 ohms of resistance means the black wire is properly grounded.
- A reading of infinite resistance means you must to find and repair the break in the black ground wiring. Once you restore a good path to ground on the black wire, you should be able to start the engine.
Check the fuse
If the ground side of the circuit is okay, you’ll need to check the hot side of the circuit that begins with the small red wire on the starter solenoid terminal and ends at the white wire that connects to the coil spade.
The circuit includes a fuse, the ignition switch, brake switch and blade switch.
First, check for a blown fuse because you can usually see a blown fuse just by looking at it.
The fuse on most riding mowers is connected to the small red wire that connects to the starter solenoid post. Check the fuse and replace it if it’s blown. If you replace the fuse and it continues to blow, you’ll need to find the short in the wiring or component that’s causing the fuse to blow. Our Troubleshooting a Blown Fuse video will walk you through the steps to find the cause of a blown fuse in a riding mower.
If the fuse is okay, reinstall it in the holder.
Test the ignition switch
Check continuity through the red wire from the starter solenoid post to the ignition switch. You should measure near 0 ohms of resistance through this section of wiring. If you measure infinite resistance, find and repair the break in the red wire.
If the wire going to the ignition switch is okay, check continuity through the internal ignition switch contacts as shown in the video. Replace the ignition switch if it’s bad.
Check the interlock switches
If you haven’t found the cause of the starting problem by now, you’ll need to check the brake and blade interlock switches as shown in the video. Finding and replacing a bad interlock switch may help you get your riding mower started.
Troubleshooting starting problems on a riding mower can be a tedious and complicated task for a novice DIY’er. Whenever you get to a point where you need to have a Sears Technician diagnose and repair your riding mower, you can schedule service on our Sears Home Services repair page.
Riding Mower Clicks but Doesn’t Crank
When you hear a click as you turn the key, a weak battery, bad starter solenoid, faulty wiring, failed starter motor or a seized engine could be the cause. This DIY troubleshooting will help you figure out what to fix.
The video shows how to:
- Check for a weak battery.
- Check the battery cables.
- Test the starter solenoid.
- Test the starter cable.
- Check for a seized engine.
Performing these tests should reveal the cause of the engine starting failure so you can fix the riding mower.
Engine Spins but Won’t Start
When the engine spins but won’t start as you turn the key, the engine is missing one of its key requirements for starting—fuel, compression or spark. Watch this DIY troubleshooting video for tips to get the engine started.
Check to see if the engine has compression and spark by spraying a short burst of starter fluid into the engine’s cylinder as shown in the video. Turn the key to start the engine. The highly combustible starter fluid will start the engine briefly if the cylinder gets spark and the right amount of compression.
If the engine starts briefly and then dies, you know the spark and compression are okay, leaving you with a fuel supply problem. You may need to rebuild or replace the carburetor to restore a good fuel supply to the engine. Once you fix the fuel supply problem, the mower should start and run properly.
If the mower doesn’t start with the help of starter fluid, continue to troubleshoot the problem using the tips in the video.
Avoid starting problems altogether by scheduling professional Riding Mower Maintenance every spring. Our Sears Technician will visit your home to inspect, lubricate and test parts on your riding mower so that it’s ready for the mowing season. The technician can identify and fix any problems before they lead to a breakdown.
Trust Sears to help you keep your lawn and garden equipment in top shape.