Why does your mower run and then die? And how can you tell what the issue is?
If a lawnmower runs and then dies, it may be because the carburetor is dirty, the gasoline is bad, there is an issue with the spark plugs, too much or too little oil, a clogged air filter, dull blades, or a build-up of grass and debris. Take apart and examine each part to troubleshoot.
Now that you know what issues can cause a lawnmower to stop working, you may be wondering how you can troubleshoot and diagnose each problem, as well as how to fix it. Don’t worry, we’ll go into each potential issue and how to fix it yourself.
What Is Causing My Lawn Mower to Die After Starting?
Dirty, Clogged, or Loose Carburetor
If you think that the carburetor is causing your lawnmower to stop after it has started, you will need to look at the actual carburetor. If the carburetor seems to be loosely attached to the lawnmower, then it is probably the cause of your lawnmower not working. Read how to fix this issue in the “How To Fix A Lawn Mower” section.
If you look at the carburetor and it is not loose, but it is very dirty, then the carburetor is likely the cause of your lawnmower suddenly stopping. Read how to fix this issue in the “How To Fix A Lawn Mower” section.
Not Enough Gasoline or Dirty Gasoline
If you have not used your mower in a long time and have not replaced the gasoline that is in the gas tank, the gasoline is most likely the issue that is causing it to stop working. I can’t tell you how bad old gas is on an engine!
If you have left your mower in a moist place for a long time, then there may be moisture in the gas tank that is causing the problem. Think about when you last used your lawnmower, and when you refilled the gas tank.
Read how to fix these issues in the “How To Fix A Lawn Mower” section.
Too Much Oil or Dirty Oil
If you have not changed the oil in a long time or your mower has been sitting unused for a long time, then the old oil probably is the issue. If you have filled the oil recently but the engine has suddenly stopped working, then your mower’s oil container may be overfilled.
Make sure that you regularly change your mower’s oil if you use it regularly. A lawnmower should have its oil changed roughly every season of use. Old oil can be really bad for an engine and can cause it to break down sooner than it should.
Read how to fix this issue in the “How To Fix A Lawn Mower” section.
Dirty or Broken Spark Plugs
If the spark plugs are dirty or broken then your mower may stop working suddenly. To diagnose this issue, turn off and let’s have a look at the spark plugs. Take the plug out and see what it looks like. If it is really dirty or seems to be broken, then that is likely causing your mower to stop working.
The spark plugs could also be loose, so check to see if they are loose. If the spark plugs are loose, then insert them tighter to remove any wobble.
Read how to fix this problem in the “How To Fix A Lawn Mower” section.
Dull or Bent Lawn Mower Blades
It is very easy to diagnose whether or not your mower’s blades are causing it to suddenly stop working. If you think that the blades are dull, broken, or bent, make sure the machine is completely turned off. Then tilt it and put it on the ground so you can see the blades. If the blades seem to be dull or bent, then the blades are likely causing it to stop working.
If they don’t seem to be dull, broken, or bent, but it seems like the blades and deck is clogged, then this is likely causing it to suddenly stop working. If the blades can’t move, or your mower can’t take in any more grass because it is clogged, then it will stop.
Read how to fix these issues in the “How To Fix A Lawn Mower” section.
Dirty or Clogged Air Filter
If you think that the air filter is causing your lawnmower to suddenly stop working, make sure that it is completely turned off and have a look at the air filter. If it is dirty or looks like it is clogged, this is likely the cause, and it is a relatively easy fix.
If your air filter is not clogged or dirty, look at the gas cap. In the middle of the gas cap, there should be a vent or plug of some sort. If that seems to be clogged or dirty, then the gas cap is most likely causing your mower to suddenly stop working. Luckily, this is very easy to fix.
Read how to fix these issues in the next section.
How to Fix a Lawn Mower
If the carburetor is loose, then remove the parts holding the carburetor to the lawn mower until you find the loose part. When you find the loose part, tighten or replace the part. After the loose part has been tightened or replaced, put all of the parts back where they belong on the mower and fully tighten all of the screws and bolts.
If the carburetor is dirty or clogged, remove the carburetor and clean it. You can use soap and water, but it is best to clean the carburetor with a carburetor cleaner (link to Amazon). After the carburetor is completely clean, reattach the carburetor and fully tighten the screws and bolts holding the carburetor to the lawn mower.
Pro tip: Another sign that the carbs may be dirty or clogged is if the mower will only run on choke.
If you have not used your mower in a long time and it has stopped working, make sure that it is completely off and remove the gas tank. Your lawn mower’s Owner’s manual will have instructions on how to access and remove the gas tank. After you have removed the gas tank, drain it into a bucket and properly dispose of it at a later time. After the gas tank has been drained, re-attach it to your lawn mower and fill it with gasoline.
If you suspect that there is moisture in the gas tank, the gasoline in the lawn mower will need to be drained and the gas tank completely dried out. After the gas tank is completely dry, re-attach it and refill it with new gas.
If you suspect the oil is causing your mower to suddenly stop working, and you have not used your it for a long time, then change the oil. Your Owner’s Manual will have specific instructions on how to change the oil.
If you have changed the oil recently, then you may have filled up the oil container too much. Check the oil container level and make sure that it isn’t overfilled. If you have filled the oil container too much, drain some of the oil into a container and properly dispose of it at a later time.
If your mower’s spark plugs seem to be causing it to suddenly stop working, make sure that your mower is completely turned off. Then, remove the spark plug and look it over. if it seems to be dirty, clean it with a gentle cleaner.
If the spark plug appears to be damaged, replace it. Your Owner’s Manual will list the specific type of spark plug that is required for your mower. If the spark plugs need to be replaced, you can find them at any local hardware store. They range in price from $4 to $5.
Pro Tip: Symptoms of a bad spark plug can also show up with a mower only starting with starter fluid.
Lawn Mower Blades
If the blades seem to be dull, sharpen them. You can find a blade sharpener at any local hardware store, and they range in price from $5 to $8, so they are relatively cheap.
If the blades are broken, replace them. Your Owner’s Manual will have instructions on how to replace the blades. source
If the blades and deck look clogged up with grass, then we need to clean it. While it’s turned off, remove all of the grass and debris that is clogging it up. You may want to wear gloves to protect your hands from the blades, any sharp or pointy debris, and grass stains. After removing all of the grass and debris, make sure to spray down the bottom of the mower with water to clean off all of the residual clippings.
Sometimes, a small piece of debris such as a rock or stick can stop the blades from rotating, which will seize the engine and not let it start. These small pieces of debris are often really hard to spot and may take some thorough investigation on your end to find them. Try checking to see if something wedged itself between the blade the and top of the blade section.
If your mower deck is very clogged, the Owner’s Manual will have instructions on how to deep clean and remove clogs.
If the air filter is dirty or clogged, simply replace it. Your Owner’s Manual will have instructions on how to do that, as the specific instructions will vary depending on your machine’s model. The Owner’s Manual will also list the type of air filter that you need to purchase. You will find the needed air filter at any local hardware store.
You may want to wear rubber gloves and a mask while you are doing this so you don’t get dust on your hands or breathe any dust in, as dirty air filters can contain a large amount of dust and other particulates.
If the gas tank air valve seems to be clogged or dirty, clean it with soap and water until it is completely clean. When it is fully dry, put it back on.
If you have replaced and cleaned everything outlined above and it is still stopping after it has started, take it to a mechanic. They will be able to diagnose the issue and tell you what it is, and whether or not it can be fixed. Although it may be expensive to pay a mechanic to fix your mower, sometimes it is cheaper than purchasing a new one.
Lawnmowers are generally quite reliable and pretty easy to fix. The majority of the time you will be able to fix the issues you might have with your mower. Once you do fix the problem, it should be a while before you have another issue.
Sometimes investing in a more premium, reliable mower brand will save you a lot of time and headache later on down the road. To understand this better, see my article on Are John Deere Mowers Worth The Money?