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Simplicity Riding Mower or Zero Turn Starts Then Dies (12 Reasons)

Having your lawn mower die in the middle of the lawn is something I’ve experienced a few times and you may have encountered this too. Below you will find many common reasons for a mower quitting while you’ve been mowing with it.

A Simplicity riding mower or zero turn starts and then dies due to a plugged air filter, dirty carburetor, faulty fuel pump, plugged fuel filter, dirty spark plug, bad ignition coil, incorrect engine oil level, plugged cooling fins, or plugged mower deck.

Keep reading for additional items that can cause your starting problem.

Follow the safety precautions found in the Simplicity operator’s manual. This includes removing the ignition key and spark plug wires. Wait for the engine to cool and for all parts to stop moving.

Plugged air filter causes Simplicity to die

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

12 Reasons Your Simplicity Mower Starts Then Dies

1. Old or Wrong Fuel

Gas doesn’t last long before it begins to break down. This can happen as soon as 30 days after purchase. Because of this, it’s best to consume fuel within 30 days.

Most gas includes ethanol. This is an alternative fuel to make gas more environmentally friendly. While ethanol is better for the environment, it is not good for your Simplicity small engine.

Ethanol naturally attracts moisture from the air and to the fuel system. The ethanol and water mixture will leave behind varnish over time that restricts fuel flow or causes component failure.

Always use a gas with a minimum 87-octane rating and maximum 10% ethanol content. Stay away from fuels with a higher ethanol content like those sold as E15 and E85.

Add a fuel additive like Sea Foam Motor Treatment to keep gas stable a little longer. This is a product that must be added to fresh gas. It cannot reverse the effects of old gas.

You can read more about the advantages of Sea Foam in Use Sea Foam Fuel Additive in a Lawn Mower to Stabilize Fuel.

SOLUTION: If you are running your Simplicity with old fuel, drain the fuel from the tank. Fill with fresh fuel and a fuel stabilizer developed to help clean the fuel system and reduce moisture.

2. Plugged Fuel Filter

An inline fuel filter is placed between the fuel lines to strain fuel as it comes out of the fuel tank to keep dirt and other contaminants out of the fuel system.

This is a maintenance part that should be replaced annually to keep it in good condition. When it isn’t, the filter can become plugged keeping a good flow of fuel from being able to pass through it.

A lack of fuel will cause your Simplicity to run sluggishly and possibly die.

SOLUTIONReplace a clogged fuel filter. When installing the new filter, pay attention to the arrow found on the plastic housing of the filter. The filter must be installed with the arrow pointed in the direction of the fuel flow.

3. Blocked Fuel Lines

Just like your carburetor can become clogged from running bad fuel, your fuel lines can also become plugged. Ethanol attracts moisture in the fuel system.

When that moisture evaporates, it leaves behind a gummy substance that can stick to the fuel line. This can cause a narrowing or complete blockage that will keep sufficient fuel from getting to the carburetor.

Identify a clogged fuel line by using the fuel shut-off valve to start and stop fuel flow while checking for a good flow of fuel coming out of the fuel line.

SOLUTION: Once you identify a section of the fuel line that is clogged, shut off the fuel supply and remove the line from the mower.

Spray carburetor cleaner into the line. This is used to loosen the blockage. Follow this by blowing compressed air into the fuel line to remove the clog.

Repeat if necessary. If you are unable to remove the clog or find the fuel line is developing cracks, replace the line with a new section of fuel line of the same diameter and length.

4. Faulty Fuel Pump

A fuel pump is required when the carburetor sits higher than the fuel tank. This is because fuel can’t run uphill without the assistance of a pump.

A bad fuel pump is another item that may have caused your Simplicity to quit running. A vacuum fuel pump uses the vacuum off the engine to move fuel from the fuel tank to the carburetor.

When the pump is broken or cracked, it will fail and needs to be replaced.

SOLUTION: Identify you have a faulty fuel pump by using your fuel shut-off valve or clamps to start and stop fuel flow as you test your fuel lines for fuel flow.

Once you have identified you are getting fuel to the pump, you will need to test the pump to see if fuel is being pumped out to your carburetor.

Do this by removing the fuel line from the carburetor and placing the line in a container. Start your lawn mower and watch the fuel line in a container to check for fuel coming out of it.

You will want to see a steady or pulsating flow of fuel to know your fuel pump is operating as designed. Replace a fuel pump that has cracks in it or is no longer able to pump fuel to the carburetor.

5. Dirty Carburetor

The carburetor is used to mix the right amount of gas with air needed for combustion. When it fails to function correctly, the mower may die.

The varnish left behind from old fuel can clog fuel passageways and cause internal components to stick or corrode. This is a common problem when using fuels that contain ethanol.

SOLUTION: When the engine isn’t getting gas because of a dirty carburetor, the carburetor must be removed and cleaned to remove buildup and replace damaged parts.

To narrow down the problem to the carburetor, first, make sure you are getting fuel to the carburetor. If you are not, check for fuel restrictions in the fuel filter, fuel lines, or fuel pump.

Next, remove the air filter and spray carburetor cleaner into the air intake.

If the mower starts and runs fine while burning the carburetor cleaner and then dies, the cause of your dying problem is most likely the carburetor.

If you are mechanically inclined you can try to clean the Simplicity carburetor. A lawn mower repair shop will be able to help you clean or replace the carburetor if you don’t want to tackle the job.

6. Bad Gas Cap

The fuel tank vents through the gas cap on a Simplicity mower. When the cap is broken or the vent is plugged and no longer allows air to pass through the cap, the fuel tank will form a vacuum.

This vacuum will keep fuel from flowing out of the fuel tank and moving to the carburetor. If you’re mower runs for a while, eventually dies, and you can’t find any other cause, you need to check the fuel cap.

A good way to identify a fuel cap problem is to loosen the fuel cap to allow air to flow into the tank. Then start the mower and allow it to run.

If the engine starts and runs fine, try to replicate the problem by tightening the fuel cap and continuing to run the mower. If the mower sputters and dies again and won’t restart until you allow air to get to the fuel tank, you most likely have a bad fuel cap.

SOLUTION: Replace a bad cap with a new Simplicity fuel cap.

7. Plugged Air Filter

Something as simple as a plugged air filter can cause your Simplicity to shut off. Your engine requires clean air to operate efficiently.

When the air filter is plugged with grass, dirt, and other debris, it can cause your engine to overheat because it is no longer able to get the air it requires.

Using a dirty air filter won’t only cause your mower to stop when running, but it can also cause extensive engine damage. Spending a little money to keep a clean air filter in your engine can save you a large engine repair or replacement bill down the road.

SOLUTION: Remove the air filter from the air filter housing making sure not to knock any loose dirt into the air intake. If your air filter is a paper filter, knock the dirt out of the filter by tapping the filter against a solid surface.

Hold the air filter up to a light and make sure you see light through the filter. If you see light, that means air is still able to pass through the filter.

You will need to replace the air filter if you are unable to see light through the paper filter or the filter is damaged or very dark in color.  

Wash a foam pre-filter with a mild detergent and water mixture. Allow to air dry and install the pre-filter around the primary paper filter.

Your Simplicity lawn mower may use a different style of air filter. For cleaning procedures for other types of filters, read this article on air filter differences

8. Dirty or Damaged Cooling Fins

Cooling fins can get packed with dirt, grass, and oil. When the fins break or become packed with debris, the fins are not able to effectively circulate air around the engine block and cylinder head to keep your engine cool. 

SOLUTION: Remove the engine cover and clean the cooling fins. Replace any damaged fins. Ensure the heat shield is attached correctly.

9. Dirty Spark Plug

A fouled spark plug can cause intermittent spark causing the mower to die. Remove the plug and inspect its condition.

SOLUTION: Replace a spark plug that is very dark in color or is worn or damaged. If it is in good condition and only a little dirty, you can clean it with a small wire brush and reuse it.

When I’m having problems with a mower, I replace the spark plug to rule it out as the problem. A spark plug is an inexpensive part that affects the mower’s performance.

Ensure the spark plug is gapped correctly and the spark plug wire is securely attached. Either of these items can also cause the mower to quit running.

10. Bad Ignition Coil Causes

When the ignition coil gets hot, it can stop working causing your lawn mower to quit running. The windings on the coil can separate and short out.

A bad ignition coil will not be able to provide sufficient voltage to the spark plug.

SOLUTION: Make sure you are using a good spark plug. Use an ohmmeter to test your ignition coil to confirm there isn’t a break in the continuity. Replace the coil when you find your ignition coil is bad.

11. Too Much Engine Oil or Too Little Engine Oil 

Too much oil in your Simplicity lawn mower can cause your engine to smoke and die while mowing. The smoke can clog your air filter causing your engine to look elsewhere for air. 

Too much oil in your lawn mower can cause significant damage including internal engine damage and the possibility of having to replace your engine.  

Too little oil in your Simplicity mower will cause additional friction in the engine that can cause your engine to overheat and die

SOLUTIONPerform your engine oil change according to Simplicity’s recommendations. Always fill oil to the correct oil fill levels.  

12. Plugged Mower Deck & Dull Blades

A Simplicity mower deck that is packed with grass and dirt or a deck that is running dull blades can cause your engine to have to work harder.

Your blades may need to turn through debris causing the engine to have to work harder. This can make it overheat and shut down. Adding dull blades to a plugged mower deck further magnifies the problem.

SOLUTION: Inspect your mower deck for any damage. Scrape the deck to remove debris and sharpen the blades. Always run your mower at full throttle when cutting grass. Avoid cutting wet grass.