Your Exmark Lawn Mower Starts then Dies While Running (Solved!)

It is so frustrating when you’re out mowing the lawn and your zero turn just stops running. You might be able to find a way to limp it along or push it back to your garage or you might be stuck troubleshooting your mower problem in the middle of your yard.

An Exmark may start and then die while mowing when the mower is no longer able to get fuel or air to the engine due to plugged filters, clogged fuel lines, a bad fuel pump, or a dirty carburetor.

An insufficient engine oil level, clogged cooling fins, and a plugged mower deck can also cause your Exmark to stop running.

I hope this list of causes helps you determine the reason why your mower stopped running. Follow safety precautions and remove the spark plug wire before performing repairs.

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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.

14 Reasons Your Exmark Mower Dies While Mowing

Fuel Tank is Empty

Not having fuel in your tank is worth mentioning because a mower will not run without fuel. Check your fuel gauge. This may be a visual gauge or your fuel gauge may show on your display.

Repair: Fill your fuel tank with the appropriate fuel for your mower.

Bad Gas

If you’re running a gas-powered mower, it’s helpful to know gas can go bad relatively quickly. Gas has about a 30-day shelf life before it begins to break down and become less effective.

The ethanol content in your fuel can have negative effects on your fuel system including attracting moisture. When this moisture evaporates, it can cause gumming which clogs your fuel system and causes your zero turn to die while mowing.

In addition to clogging, the ethanol and water mixture will eventually separate from the gas and sink to the bottom of the tank. This can cause significant engine damage when run through your engine.

Here are tips to ensure you get the best fuel results:

• Buy and use your gas within 30 days
• Buy gas from busy gas stations
• Don’t leave your fuel outdoors where it can attract moisture
• Store your fuel in a dry place
• If you are unable to use your fuel within 30 days, add a fuel additive to stabilize your fuel. I use a product called Sea Foam Motor Treatment. It’s a petroleum-based product that won’t harm your engine. It stabilizes your fuel, removes moisture, and cleans your fuel system. To read more about using Sea Foam in your lawn mower, visit “Why Use Sea Foam Fuel Additive in a Lawn Mower”. 

Repair: Remove the old gas in your mower by draining your fuel tank. Refill with fresh gas that includes a fuel additive to clean your fuel system and stabilize your fuel.

Dispose of your old gas at an appropriate recycling facility. Do not dump fuel onto the ground.

Wrong Fuel

Many gas stations are offering more types of fuels today than they did 10 years ago. You can find unleaded gasoline with ethanol contents of 10%, 15%, and 85% known as E10, E15, and E85 respectively.

Most gas stations will carry diesel fuel while some stations now carry recreational fuel known as REC-90. REC-90 is a non-ethanol fuel.

To avoid purchasing the wrong type of fuel, read the decals placed on the fuel pump to check the octane rating and ethanol content in the fuel.

Your gas-powered Exmark mower requires unleaded gasoline with a minimum octane rating of 87 and a maximum ethanol content of 10%.

The less ethanol content, the better. Never purchase gas with a greater level of ethanol as it can compromise the life of your mower’s engine.

For a more in-depth look at the best types of fuel to use, check out my article “This is the Gas to Use in Your Mower“.

Repair: Drain the fuel tank. Flush the fuel tank and fill it with fresh fuel treated with Sea Foam Motor Treatment or another fuel additive that will clean your fuel system. 

Dirty Carburetor

Your carburetor can become dirty causing your mower to die while running. The carburetor’s main function is to regulate the amount of gas and air allowed into the engine cylinder to form combustion.

When the carburetor gets clogged with gummy and white crusty deposits from running old fuel and fuels with ethanol, the components in your carburetor can fail to regulate the fuel and air mixture.

Repair: If you are mechanically inclined and don’t mind working with small parts, you can disassemble your carburetor and clean it with carburetor cleaner to remove as much of the deposits as you can to free up the parts and unclog the jet.

You may find your carburetor is too dirty or internal parts are broken. In this case, you have the option to rebuild or replace the carburetor. Read my steps on how to clean the Briggs, Kawasaki, Kohler, or Exmark engine carburetor here.

Bad Fuel Pump

You will have a fuel pump on your mower because the carburetor is located higher than the fuel tank. The fuel pump pushes fuel flow to the carburetor.

A vacuum-pressured fuel pump can stop working causing failure to build the pressure it needs to keep your fuel flowing. Look for external signs that your pump may be bad. This could be small cracks or fuel leaking from the pump.

When you don’t notice any external reasons for a bad pump, troubleshoot your fuel pump to confirm you have fuel flow to the pump and then check for a steady or pulsating flow of fuel out of the pump.

Do this using your fuel shut-off valve or fuel hose clamps to stop and start the fuel flow.

Repair: Replace your fuel pump if you are not seeing a steady or pulsating flow of fuel from the outlet port on the fuel pump.

Plugged Fuel Filter 

Your fuel filter can become plugged with dirt and build up from old fuel. Not every fuel filter is created the same and there are filters designed specifically for your engine.

Confirm you are running the correct fuel filter and that it is installed correctly. Many fuel filters have a small arrow located on the plastic that shows the direction the fuel is to flow through the filter.

Make sure fuel is flowing through your filter and it’s not being restricted due to being dirty or clogged. When your engine is starved of fuel, it can cause your mower to die while you are in the middle of your lawn-cutting job.

Repair: Replace the fuel filter if you find your filter is plugged. A fuel filter is not that expensive compared to other routine service maintenance parts.

I change mine out every year so I have the peace of mind that a filter isn’t going to cause an issue with my Exmark.

Clogged Fuel Lines 

While you were checking for a failed fuel pump or bad fuel filter, you may have found a fuel restriction problem in one of your fuel lines.

Repair: To clear the line, remove the fuel line and spray some carburetor cleaner in the hose to help loosen the clog. Next, blow air through the line using a can of compressed air until the clog is removed.

Reinstall the line. If you can’t get the clog removed or you find your fuel lines are dry and cracked, you can easily replace it with a new fuel line purchased online or your local hardware store.  

Bad Gas Cap 

Your gas cap is designed to vent allowing air to pass through the cap. When this vent is plugged, gas will not flow out of your fuel tank because a vacuum is formed restricting fuel flow. Again, when your mower doesn’t get fuel, it won’t run.

You can confirm you have a fuel cap problem by running your mower with and without your cap. If your mower runs fine without the fuel cap but eventually shuts down when you have your cap installed, you may have a clogged cap.

Caution: Do not allow dirt and debris to enter the fuel system when you don’t have your cap installed.

Repair: If you are unable to unclog the vent by cleaning, you need to replace your gas cap.

Plugged Lawn Mower Air Filter  

Another filter that can get clogged on your lawn mower is the air filter. This is an important filter as it keeps contaminants from entering your air intake and getting into your engine.

Dirt and other materials in your engine can cause significant damage.

Your engine requires clean air. When the air filter becomes so plugged with grass clippings and dirt that it no longer allows air to pass through the filter, the engine cannot get the air it needs. Your mower will die and shut down because of the lack of air.

An excessively dirty air filter not only will cause your zero turn to not run, but it can also cause extensive internal damage.

When your mower is unable to pull air through the air filter, it may result in finding the only available air in the crankcase. This can pull air and oil into the cylinder causing your mower to smoke and overheat.

For the longevity of your Exmark’s engine, it is necessary to check your air filters regularly. You must clean it or replace your air filter if needed.

Because I know the damage that can occur from something as simple as a dirty air filter, I check mine about once a month. It only takes a couple of minutes.

Remember, air filters become dirty sooner when you are mowing in dusty conditions.

Repair: Remove your paper air filter. Knock as much dirt as you can remove from your filter by tapping it against a solid surface. Hold your air filter up to the light to check for light shining through the paper element.

Reuse your air filter if you can see light. You must replace your air filter with a new filter if you can’t see light. Before replacing your filter, wipe out any dirt or debris in the air filter housing. Be careful not to allow any dirt to fall into the air intake.

Dirty Spark Plug

A fouled spark plug can cause your zero-turn to die. Check your mower for a spark plug that is dirty or isn’t correctly gapped. Loose spark plug wires can also cause your mower runs sluggish or dies.

SOLUTION: Remove your spark plug and clean the spark plug if it is dirty. If it happens to be very dark in color or damaged, install a new spark plug.

Make sure it is correctly gapped according to your engine manufacturer’s specification and the spark plug wires are securely attached.

Bad Ignition Coil

The winding on the ignition coil can separate and short out when your mower is hot. When this happens, the spark plugs are unable to get the voltage they need to create a spark.

This can cause your mower to die after it’s been running for a while.

SOLUTION: Identify a bad ignition coil using an ohmmeter to check for a break in continuity. Replace the ignition coil if you find there is a break.

Dirty or Damaged Cooling Fins

Your Exmark uses a fan on the top of the engine to push air down your engine block and cylinder head.

The cooling fins help dissipate heat. The engine can overheat when the cooling fins become dirty.

Repair: Remove the engine cover and clean the cooling fins. Replace any damaged fins on your Exmark mower.

Too Much Oil or Too Little Oil

The full oil line on your engine oil dipstick isn’t just a suggestion. You must keep your engine oil at the full level.

An oil level that is higher or lower than this can cause your engine to smoke and die while running. The smoke can clog your filter restricting airflow to the engine.

Too high of an engine oil level can cause internal engine damage. You need to remove excess oil by using one of these methods:

• Use an evacuator to vacuum out the oil
• Unscrew your filter and remove oil from the filter
• Remove your oil drain plug and quickly replace it to only allow a small amount of oil to be drained
• Use a turkey baster (yes, like the one from your kitchen) to suction out a little fuel from the oil-fill area

To read more about the damage too much oil can do to your zero turn, read my article here.

Too little oil in the crankcase will not give your engine parts the lubrication they need to move freely.

When there isn’t enough lubrication, friction among the moving parts increases which causes heat to build up within the engine. This heat can get so hot your parts begin to melt and your oil becomes very hot and thick.

Repair: Perform your engine oil change according to the engine manufacturer’s recommendations. Always fill oil to the correct oil fill levels. 

If you continue to have problems once you have brought your crankcase to the correct oil level, bring your mower to your authorized Exmark dealership or a good small engine mechanic to identify your internal engine problems.

Plugged Mower Deck & Dull Blades 

When assessing why your mower dies after starting, you tend to first think about fuel, air, and oil affecting your engine.

You may overlook the fact that your mower deck can put an extra draw on your engine when it is not operating as it should.

An Exmark deck is known for its cutting performance. Not only will a packed mower deck and dull blades affect your cut, but it causes your engine to work harder.

Mower blades that need to work through a deck that is full of mud and dirt can cause your engine to overheat and shut down.

Repair: Inspect your 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 or very tall grass.