If you are experiencing trouble with your Simplicity zero-turn mower, you can find some tips in this article to diagnose the problem.

Often, the issue can be as simple as a bad switch or solenoid, or it could be something more complex like a dirt-filled air filter.
In either case, the first step is to check the oil level, which should be at least half full.
To further troubleshoot the problem, you can also check the hoses and connections.
If possible, clean the pump cooling fins with a rag or compressed air.
Troubleshooting a Simplicity Zero-turn Lawnmower
There are many ways to troubleshoot a Simplicity zero-turn lawn mower, including checking the battery.
Ensure that the battery is fully charged and make sure the battery terminals are tight. If the mower still doesn’t start, check the starter solenoid.
This small component can suffer from problems and should be checked by a small engine mechanic. To ensure the safety of your mower, never attempt to start it on your own.
Check the fuel filter
Next, check the fuel filter. This filter strains the fuel that enters the engine. When it becomes plugged, it may no longer be able to regulate the fuel. Make sure you check the fuel filter’s housing and replace it if needed.
You can also look for an arrow on the filter housing, pointing in the direction of the fuel flow. If you don’t see this, then the fuel filter is blocked.
If you can’t start the engine, you can try to bypass the safety switch. This will help you find out if the ignition coil is the problem.
The ignition coil is responsible for providing voltage to the spark plug. If you find that the coil is broken, you’ll need to replace it. You can also check the oil level. Make sure that hoses and connections are secure.
Check the hydrostatic transmission
The next step is to check the hydrostatic transmission. Hydrostatic transmissions in zero-turn mowers can suffer from cavitation, or air in the system.
Air in the system can cause the motor to run slow or not at all. If this is the case, try to purge the transmission. In addition, make sure to park the mower on a level ground and the mower is on jackstands.
Checking for a bad switch
Most modern mowers have an ignition switch. This is a small circuit with relays and resistors that send a start/stop command to the engine.
The switch will only engage if all sensors are engaged. If it doesn’t, you should contact a service technician. They will help you identify the problem.
If you’re having problems starting your Simplicity zero-turn mower, the problem might be with the engine’s starter.
You can test this yourself by redistributing your weight on the seat. The emergency brake switch is another common culprit.
It prevents the mower from starting when the operator is out of the seat. If this switch does not work, it’s time to contact a small engine mechanic for diagnosis.
A bad ignition switch can be easily replaced by unscrewing the front cover of the mower. To do this, disconnect the negative cable from the mower’s battery and locate the seat switch.
The seat switch will be attached to a metal bracket and contain a solenoid. If the wires are crossed, they’re likely to stop the mower from starting. In some cases, the switch may be shorted to the seat or plug.
PTO Switch problems
If the engine starts and stops suddenly, it’s likely the PTO switch has a problem. If this is the case, check the starter solenoid.
This is responsible for connecting the battery to the starter motor. If the solenoid clicks, the circuit is functioning properly.
A broken or loose connection in this part of the machine might also be the cause of the problem. Once this is fixed, replace the PTO pulley and start your Simplicity zero-turn mower.
Checking for a bad solenoid
First, look under the mower hood to make sure the starter solenoid is working properly. The small wire from the solenoid to the mower’s metal frame is its negative terminal.
Plug a test lite or meter into the small wire and measure the 12 volts. If there is no voltage, check the battery. If the battery is working correctly, you should see four amps. Otherwise, the starter solenoid is the culprit.
Next, check to see if the solenoid has a clicking sound. If you do not hear a click, you need to replace the solenoid.
Turn the key to the ignition and listen carefully to the solenoid’s voltage. If it is reading very little voltage, it’s time to replace it. The solenoid is the most likely cause of the clicking sound when you start the engine, so it’s vital to check it if it’s a problem.
If you’ve already checked all of the electrical wiring on the mower, you’ll find a faulty solenoid. The solenoid triggers the engine’s starter motor and is located on the engine’s front side.
The solenoid contains three or four threaded electrical lugs. A bad solenoid will cause the engine to stop and turn on and off.
If you notice that your engine isn’t starting at all, a bad PTO solenoid could be to blame. It has to supply so much power to the PTO clutch, which may have seized up. Other symptoms may be a bad clutch, a stuck blade, or a seized PTO pulley. If none of these symptoms apply, you’re looking for something more serious.
Checking for a dirty air filter
If you notice that your Simplicity zero turn mower is sputtering, oily, or emits black smoke, the first thing you should do is check the air filter. If it’s dirty, you need to replace it immediately.
Dirty filters can reduce fuel efficiency and result in additional gas consumption. You can also start to notice a decrease in performance.
To clean your air filter, start by examining the paper pleats. If you see moderate dirt, you can simply wipe them clean. If the paper pleats are caked in dirt or discolored, it’s time to replace them.
Similarly, if you’re using an all-foam filter, you should wash it with warm soapy water. Then, wipe it dry thoroughly.
You can also check the ignition switch. The switch is a basic electrical component and performs the function of starting and stopping the engine. To test the switch, you can use a digital voltmeter.
The number of pins in the rear of the switch will vary by model. Look for visual damage. If you see signs of corrosion, call a mechanic. If you’re still unsure, try switching off your mower and repeat the test.
The air filter on your mower should be cleaned about every 25 hours. Most models feature easy access to the filter, but the metal plug cap can easily become loose. The metal plug cap connects to the air filter via a push-on fitting.
When it comes time to replace the filter, make sure to use a spark plug wrench to remove any debris or dirt. If you still notice problems, it’s likely that you have a dirty air filter.
Checking for a faulty switch
When your Simplicity zero-turn mower won’t start, one of the first steps you should take is to check the ignition switch.
A bad ignition switch can prevent the engine from starting or make the mower hard to start. During this check, you can use an ohm meter to determine if the switch is bad or faulty. If it’s damaged, replace it.
A faulty switch on a Simplicity zero turn lawn mower may result in an inability to start. If the engine doesn’t start, the charge may be too low or the battery may not be able to hold a charge.
Check the battery level and replace the battery if necessary.
Depending on your Simplicity zero zero-turn mower model, there may be three different safety switches.
The first safety switch controls the blades and is designed to prevent them from turning when the machine starts. The second safety switch ensures that the mower is in neutral before the operator gets on the seat.
If you suspect that the ignition switch is the problem, you can replace it with a new one. To do this, remove the engine covers.
You can then measure the air gap between the flywheel and the new coil. If the air gap between these two pieces of metal is too large, you can use a business card to measure it.
The replacement coils are available from Amazon.
Summary
Another way to diagnose a faulty ignition switch on a Simplicity zero turn mower is to disconnect the battery and disconnect the negative cable.
If the battery is disconnected, the mower won’t start, and it won’t have a power source.
Check the ignition switch to make sure it’s working properly. If it isn’t, contact Simplicity customer service.