No one likes it when their riding lawn mower starts and then quits mowing in the middle of their lawn. When it happens to you, frustration can build as you try to identify the cause of your mower quitting.
There are so many different things that can cause your mower to die. I’ve put together a list of items to check when looking for your problem. I hope this will take away a little bit of your frustration and help you get back to mowing again.
A riding lawn mower will start then die due to old gas, dirty carburetor, clogged fuel line, plugged fuel filter, plugged air filter, dirty spark plug, faulty ignition coil, insufficient engine oil level, or plugged cooling system.
Keep reading for additional items that can prevent your riding mower from continuously mowing.
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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.
Reasons Your Riding Lawn Mower Starts Then Dies: Troubleshoot & Fix
1. Bad, Old, or Wrong Fuel
Running good fresh fuel through your riding mower is best. Gasoline can begin to break down and become less effective as soon as 30 days after purchase.
Ethanol in your gasoline along with the moisture it attracts can gum up the fuel system causing clogs. When this happens, your lawn mower starts then dies.
Another reason your mower may die is when the wrong fuel is run through your riding mower. Your riding lawn mower requires unleaded gasoline with a minimum octane rating of 87 and a maximum ethanol content of 10 percent.
Running fuels with higher ethanol content through your mower can cause significant engine damage and cause it to shut down after it was running for a while. The lower the ethanol content the better.
Ethanol is an environmentally friendly fuel option added to gasoline. It is okay to run through vehicles, but not a good option for the small engines in riding lawn mowers. Read more about the right fuel for your riding mower and the effects of ethanol here.
Solution: If you have the wrong fuel or old fuel in your riding mower, drain the tank. A fuel siphon works great for this. Just have an approved gas container available for a place to drain old fuel.
2. Dirty Carburetor
The carburetor is required on your riding mower to regulate the correct air-to-fuel mixture allowed in your engine to form combustion.
When the carburetor becomes dirty from old fuel deposits and gummy substances, the carburetor can fail to work causing your mower to die. It can’t get the air or fuel needed to continue to run.
A dirty carburetor must be cleaned to get it to work properly. To confirm you have a dirty carburetor so you don’t take it apart when you don’t need to, follow these quick steps:
- Remove the air filter from your filter housing.
- Spray carburetor cleaner into the air intake.
- Attempt to start your riding mower.
- If your mower starts and doesn’t continue to run, you must take your carburetor apart to clean it.
Solution: Cleaning your riding mower carburetor isn’t a very complicated procedure. If you are a little mechanical and don’t mind working with small parts, you should be able to handle cleaning your carburetor following the steps in this article.
If you don’t want to tackle the job, bring your mower to a small engine repair shop to be cleaned or rebuilt.
3. Clogged Fuel Lines or Fuel Filter
The substance left behind by old fuel can get stuck in your fuel lines and prevent fuel from moving through the lines and to your engine.
Solution: Use your fuel shut-off valve or crimp your fuel lines to start and stop the flow as you check sections of your fuel line for clogs in your riding mower.
Once you find a section that is clogged, remove the line and spray carburetor cleaner in the line to loosen the clog. Blow out the line with compressed air.
If you are unable to remove the fuel clog, you must replace your fuel line.
4. Blocked or Broken Cooling Fins
Engine cooling fins are necessary to circulate air around your engine block and cylinder head to keep it cool.
The cooling fins can become plugged with dirt and grass clippings preventing them from having good surface areas to dissipate heat. This can cause your engine to overheat and shut down after it has been running for a while.
Solution: Clean around your fins and replace any broken fins. Remove debris around your engine. Be careful when working around a hot engine.
5. Too Much Oil in the Crankcase
Overfilling the engine crankcase with oil will cause pressure to build in the crankcase. The crankshaft and the rod must push through extra oil. This increased pressure can cause your riding mower to overheat and die.
Too much oil can also cause your riding mower to push oil through the valve train and into the cylinder. This oil will begin to burn off creating smoke. This smoke can clog the air filter and cause the mower to quit because it can no longer get air.
When too much oil is added to your riding mower, several problems can develop if the oil level isn’t corrected. Find out more about the negative results of too much engine oil here.
Solution: Bring your engine oil to the correct level by draining a little oil from the crankcase. There are several different ways to drain a bit of oil from your riding mower:
- Use an engine oil evacuator to vacuum a little bit of oil from the oil fill.
- Drain a little oil by removing the drain plug. Have an oil pan ready. Remove and quickly replace your drain plug so you don’t allow too much oil to drain.
- Allow some oil to drain out of the engine oil filter. Remove the filter and remove a little oil. Replace the oil filter.
- Use a turkey baster to suction oil out of the oil fill. Yes, a turkey baster, like one found in your kitchen. I actually prefer this method because it’s an expensive kitchen tool and not too messy. Don’t reuse the baster for cooking purposes. Buy a replacement for your kitchen.
Check and replace your air filter if it has been plugged with smoke. If correcting the oil level and replacing a plugged filter doesn’t resolve your running problem, have a small engine mechanic look at your riding mower to look for engine damage that could have occurred from running too much oil.
6. Clogged Air Filter
A plugged air filter that cannot allow air to pass through will cause your riding mower to die and no longer run. Your engine requires clean air to run. Because dirt and grass clipping are stirred up when mowing, your air filter element has a lot of dirt and debris to filter.
It’s important to routinely check your air filter to ensure it is clean. A plugged filter cannot only cause your mower to run sluggishly and shut down, but it can also cause costly internal engine damage.
Solution: Clean Your Mower Paper Air Filter Element
To clean your air filter, remove the filter from the filter housing. Don’t allow any dirt to fall into the air intake and wipe out any dirt remaining in the housing. Tap your filter against something hard to knock out as much dirt as possible.
Hold your filter up to the light. If you see light shining through the paper, go ahead and reuse your filter. If not, replace it with a new air filter.
7. Bad or Dirty Spark Plug
When your spark plugs become dirty with carbon buildup, they may foul out and cause intermittent riding mower running problems. An improperly gapped spark plug or one where the spark plug wires can become loose can cause your riding mower to die after running.
Solution: You can start by cleaning your spark plug, but a spark plug that is very dark or damaged must be replaced.
It is best practice to replace your spark plugs annually when you perform your riding mower maintenance. Make sure your plugs are gapped according to the engine manufacturer.
8. Bad Ignition Coil
A bad ignition coil can cause your riding mower to die once it gets hot. The windings on the coil separate and short out. When this happens, the spark plugs are unable to get the voltage needed to work properly.
Solution: Identify a bad ignition coil using an ohm meter to check for a break in continuity. If you find a break, replace the coil.
9. Choke is in the Wrong Position
Make sure your choke is in the correct position. The choke is used to allow more fuel into the combustion chamber before the engine heats up by restricting airflow. The choke exists to help a mower start when cold.
If you leave your choke on after your engine starts and heats up, your engine will shut down when it continues to receive more fuel and less air.
10. Bad Gas Cap
Your gas cap can become plugged and no longer work correctly. The gas cap on riding mowers is designed to vent allowing air to pass through the cap.
When the cap is unable to vent allowing the fuel tank to maintain the correct pressure, your riding mower can die after it has been running.
Solution: Loosen or remove your fuel cap and start your mower. If it starts and continues to run, replace the cap. Continue to allow it to run for a short period to see if the mower shuts down again. If it does shut down, there is a good chance the problem is in your fuel cap.
While you can try to clear the clog, you may end up needing to purchase a new gas cap for your riding mower.
11. Clogged Mower Deck
A mower deck plugged with grass can cause your engine to overwork and overheat making your riding mower shut down while you are mowing.
Your engine must work harder when it must turn blades through debris with every revolution. A plugged deck doesn’t allow the blades to turn freely. Adding dull blades to a plugged deck only makes the problem worse.
Solution: Regularly scrape your mower deck and sharpen your blades. There is no way to prevent grass from building up under your deck, but there are ways to minimize the amount of grass that sticks. First, don’t mow in wet conditions.
Wet grass clumps together and sticks to your deck. You can use silicone or Teflon spray to coat the underside of your deck. While this won’t prevent all grass from sticking, it should minimize the amount of grass that sticks.
In Summary
A riding lawn mower may start and then die because of items that can be prevented by performing routine annual maintenance on your mower.
Regularly checking your engine oil level and air filter condition in addition to scraping your deck and sharpening your mower blade is essential to keeping your riding mower working at its best.
Still Having Problems With Your Riding Mower?
As a lawn mower owner, when you own it long enough, you are going to run into different types of problems. This may include problems where your mower is smoking, cutting unevenly, losing power, not starting, leaking fuel, and more.
Check out this handy guide including charts for common mower problems and solutions:
Common Riding Lawn Mower Problems & Solutions.
If you are unable to fix your mower or don’t want to attempt a more complicated repair, have your local lawn mower dealership or repair shop for assistance.