My neighbor Charlie is one of those guys that gets kind of cranky when things go wrong, and he was therefore not in the best of moods when last Saturday his lawnmower started to act up. I kind of like Charlie so I decided to do some research on what might be causing his lawnmower to stop whenever it got hot. I told him I was going to try and find the possible reason for the problem, to which he just shrugged and went on kicking the lawnmower. Anyway, it gave me an excuse to go inside and stop listening to his complaining.
Typically, the reason a lawnmower stops running when it gets hot is because the air intake is bad, due to a build-up of fragments the mower has picked up. That may well be the answer, but it could also be because of some damage to the air filter, carburetor problems, or contaminated fuel.
That was the first result of my research into why a lawnmower may be running hot, but when I get stuck into something like this, I like to take my research a little bit deeper. I just like learning new stuff.
Reason #1 – Bad Air Intake
The main reason why a lawnmower tends to run hot is because it’s dirty. While in use, all sorts of dirt and debris are flying around, and it is all too easy for some of it to get into the vents and block or severely reduce the air intake. So, with no cool air circulating, the lawnmower heats up and cuts out. Now I am not the most technical person, but that makes perfect sense to me, so I put that first in my list of possible causes.
It was also an easy, non-technical fix. All that was required was to take off the casing of the mower and give it a good clean, removing all the gunk that had collected.
Later, I was talking about this to Jack, our local go-to man for mechanical problems, and he said setting up a schedule for cleaning is important. He told me that the air filter gets dirty quickly and should be cleaned after using the lawnmower for about 8 hours. The muffler should also be cleaned every 60 hours of working. This should ease up some of the reasons why the lawnmower is running hot.
Reason #2 – Vapor Locks
As I continued my research, the next thing I came across was that the vapor lock could cause lawnmower engines to stall, especially on hot days. Typically, in these cases, the lawnmower just cuts out, but if you leave it for an hour, it will start fine.
It seems that a vapor lock happens when hot gasses get stuck inside the fuel tank. These gases cause the engine to stall. So once again this problem is down to a dirty lawnmower. If the fuel cap gets dirty, then the small holes get blocked and the gases cannot escape the fuel tank.
Now, this looks like another easy fix, so that’s why I made it my number 2 suggestion.
Reason #3 – Leaving Gas in the Tank
Now this potential cause I find particularly interesting. It seems obvious that you should empty the tank on your lawnmower before you put it away.
If fuel just sits in the tank, it produces a sticky material that will clog the carburetor and fuel lines.
Most people fail to empty the tank before they put the mower away for the winter, so this could be another reason. Leaving gas in the tank over winter could also mean that you have to clean the fuel lines as well.
I was feeling impressed with myself, as I had already found three likely reasons why Charlie’s lawnmower was behaving so badly. But still, I was not satisfied and wanted to make sure I covered all the bases.
Reason #4 – Faulty Spark Plugs
The spark plugs are another potential reason why the lawnmower may be running hot. Potential problems with spark plugs are:
- Dirty electrodes
- Corroded electrodes
- Breaks in the porcelain housing
- Carbon deposits on the firing end
If you think it may be the spark plugs, you have two options. First, you can inspect and clean the existing ones. If they just seem to be dirty but otherwise intact, you can clean them using a little sandpaper. Second, you may opt to replace them with new ones (they are not expensive).
Reason #5 – Loose Bolts
Now for the final possible problem. This one is less likely to occur than the others, but I will include it just in case. Apparently, after you have had a mower for some time, the vibration can cause bolts to loosen up a little. This may allow air to get in where it should not be and disrupt the optimum air to fuel ratio, which can cause stalls.
Feeling incredibly pleased with myself, I typed up this list of possible reasons and decided to share them in this article. I am fairly certain that among the possible causes I have listed, that one of them is going to be the reason why your lawnmower is running hot.
So, maybe if you have a similar problem, trying one of these easy solutions may work for you.
Thinking that I was finished, I had a final scan through the Internet to make sure I had not missed anything. I came up with a few questions that I thought were relevant, so I added them to this FAQ.
How do you recognize a bad ignition coil?
A symptom of a bad mower ignition coil is when the engine gets hot and cuts out while mowing the lawn. If the mower is allowed to cool down, it starts normally, and then the problem repeats once it gets hot again.
How can you quickly fix a mower that runs for a while then cuts out?
If your mower runs for a short while (say about 10 minutes) then cuts out, quickly remove the gas tank cap and allow air back into the tank. Then replace the cap and the mower should start right away.
Why does my lawnmower start fine, but refuse to keep running?
There may be several reasons for this happening. First of all, check if there is fuel in the tank. If there is, then check to see that the filter and carburetor are not clogged. Then check that the fuel mixture is correct, and finally check the spark plugs.
Why does the mower stall on hills?
This could be another symptom of bad spark plugs or ignition coils. Alternatively, it could also point to a clogged carburetor.
Why does the lawnmower splutter or chug?
The most common reason that lawnmowers splutter is that there is dirt in the carburetor and/or the fuel filter, which causes an interruption of the supply of fuel.
What are the symptoms of a dirty carburetor?
There may be several symptoms that point to a dirty carburetor. These include:
- Trouble starting the mower.
- The engine stalls when you are mowing.
- The engine sounds like it is running rough.
- Black smoke seeps from the muffler.
- A clear increase in fuel consumption when mowing,
Can I use WD40 to clean my carburetor?
WD40 cleaning spray is excellent for blasting deposits and dirt from the carburetor, and it leaves no residue.
Why does the lawnmower engine cut out when the blades engage?
You should check the belt and make sure it is routed correctly. You should also check the pulleys to make sure they are not sticking or have sustained damage. Do not do this while the engine is running.
Why does my mower die when I put it in gear?
You should check the grass box safety switch. If it is not completely pushed in, it will apply the brakes when in gear.