Reviewed for compliance by small engine technician
Your lawn mower may surge a little bit sometimes when you start it, then the surge goes away. There’s nothing to worry about that.
However, if it keeps surging while you’re using it like going up and down or even dies, then you have every reason to be concerned. Although it may mow your lawn competently, the whole time you’ll probably be thinking, “why does my lawn mower sound like it is surging?” It won’t be such an enjoyable mowing session, will it?
Lack of enough supply of fuel to the engine is the usual reason behind surging. But there are also other possibilities so let’s look at the possible causes of the fuel starvation along with how you can fix them yourself.
Note: This guide would generally apply to all gas lawn mower brands such as Honda, Greenworks, Craftsman, PowerSmart, Yard Machines, Briggs & Stratton, Toro, Lawn-Boy, Columbia, Jonsered, Poulan Pro, Kawasaki, Troy Bilt and many others.
Clogged Air Filter
The air filter is the first thing you’ll want to check when looking to fix your surging mower. If it’s dirty, it starves the mower engine of the oxygen required for combustion.
Solution: Depending on the type of filter, you can clean or replace it.
- First, disconnect the spark plug wire. Always take this safety precaution before performing any repair or maintenance on your mower. This prevents it from starting and causing injuries.
- Remove the air filter and its housing.
- Use soapy water to clean a foam filter. Once it dries completely, smear a light engine oil coating over its surface to help capture dirt and prevent it from ending up in the carburetor.
- On the contrary, if you have a paper filter and it’s too dirty for you to even see light through it, replace it with a new filter that’s designed for your lawn mower model.
- Wipe dirt out of the filter housing before installing the filter.
Is the engine still surging after fitting the new or cleaned air filter? Read on to get more troubleshooting tips.
Dirty Carburetor
This the most common cause of surging issues. Grime and dirt can gum up the internal components of your carburetor, making it fail to receive the correct flow of fuel.
Solution: You can take your mower to a small engine repair shop to have the carburetor removed and cleaned. However, if you’re comfortable with your repair skills, then here are the steps you should take:
- Disassemble the carburetor. For you to reach the carburetor, you’re likely to have to disconnect the air filter, fuel tank, governor control link, breather pipe, and manifold seal and keeper ring.
- Clean the carburetor with a carburetor cleaner that’s appropriate for your mower engine, paying special attention to the needle valves, orifices, and ports. You’ll need to replace the carburetor if its body is in poor condition or damaged.
- Once you’ve given the carburetor a good cleaning, reassemble the mower components in reverse order.
Fuel System Problems
The fuel tank cap has a small hole, which allows air to flow into the tank and create back-pressure to help deliver fuel to the carburetor. Dust or dirt can plug up this hole. As a result, the carburetor won’t get enough fuel, leading to surging.
Surging can also occur due to water contaminating your fuel. Water can enter gasoline through condensation on a scorching summer day or heavy rain.
Solution: These steps can help you fix fuel system issues quickly:
- Inspect the vent on your gas tank’s cap and clean it if it’s dirty.
- Drain the gas tank, clean the gas bowl, and add a fresh batch of fuel. Or you can inject fuel cleaner to clean the fuel line.
- After changing the fuel or injecting fuel cleaner run the lawn mower as usual.
Caution: Make sure the fuel is below the maximum gauge level.
Vacuum Leaks
If your carburetor is loose, it will suck air in through the crevices between it and the engine block. The excess air will unbalance the gas to air ratio.
The imbalance will compromise the vacuum required to move fuel and air properly through the carburetor at the recommended rate, resulting in irregular engine performance.
Solution: Check the bolts on the carburetor or air intake manifold and tighten them for a proper fit.
If you still have problems with your mower after performing these fixes, it may have serious engine problems that need professional repair.
Remember, performing mower maintenance at the beginning of each mowing season will significantly help protect it from problems.
