Skip to Content

This site is an affiliate for companies including Amazon Associates and earns a commission on qualifying purchases.

Weed Wacker Engine Seized

Nothing is worse than getting up early on the weekend to go outside and get some fresh air by starting the morning with some yard work only to find your weed wacker is seizing. A seizing weed wacker is a common issue, and there are plenty of quick fixes to get it up and whacking again!

Your weed wacker engine may have seized if it does not have enough oil or gas to maintain operation. Other times, weed wacker engines seize because of a lack of airflow through the engine. Both of these issues have simple solutions.

Understanding how weed wackers work and why their engines may seize can be beneficial when doing yard work. Read on to learn more about how weed wacker engines work, why they seize, and how you can fix a seized engine.

How a Weed Wacker Works

Most weed wackers use two critical mechanisms to start the machine and keep it going. These are the pull cord and the engine itself. 

Most weed wackers use a small combustion engine to power the cutting mechanism at the bottom of the device (either blades or string). 

Combustion engines use a series of small explosions within particular chambers in the machine to cause movement, generating the energy needed for the blade to move (source).

To make this series of small explosions work, however, weed wackers need the three components of fire: heat, fuel, and oxygen (source).

To get the fuel, weed wackers pump a mixture of oil and gasoline into the chambers of the engine. Then, the fuel takes on a gaseous form. This gaseous mixture then combines with oxygen in the chamber. Then, all that needs to happen is the combustion– or heat. 

This heat comes from the spark plug. Once the chamber is full of gas and air, the spark plug releases a spark into the engine. This spark, combined with the gas and air, makes a miniature explosion that moves the chamber up and down. 

This process is done repeatedly through the chambers that make up most small engines, thus powering your weed wacker. 

Why a Weed Wacker May Seize

It is important to note that if any of the components that cause combustion is missing, the engine will not produce these explosions and start. 

If your weed wacker engine seizes as you are using it, you are likely missing one of these three components. Read on to learn more about exactly why your weed wacker’s engine may seize.

Your Weed Wacker Ran Out of Gas

In many cases, people start their weed wackers without considering the last time they used it or how much gas they left in it. 

Similar to driving a car, most of the time, you don’t realize you are low on gas unless your car begins to experience issues or you get a warning light that comes on. Weed wackers don’t have this warning light, so many people often forget to put gas in the engine, causing it to seize.

The same is true if the engine doesn’t have oil. Weed wackers, like many other small engine devices, rely on mixed gas to power the machine. If your weed wacker lacks oil, it may seize.

There Might Not Be Enough Airflow

Since combustion relies upon the presence of oxygen to ignite the fuel, if your weed wacker doesn’t have enough oxygen, the engine will seize while in use. 

Weed wackers, when burning the gas and oil, produce exhaust, a combination of carbon dioxide, carbon monoxide, nitrogen oxide, and other chemicals. This exhaust is essentially “dirty.” If it cannot escape your engine quickly enough, it prevents clean air from coming in to start the combustion process.

This exhaust also makes the parts of your engine that encourage airflow dirty. Like plaque in a human’s veins, if this builds up over time, the oxygen will not move through it, jamming up the whole system.

Your Spark Plug Might Be Too Dirty Or Worn Out

Spark plugs send a spark at a rate of nearly 400 times per minute. This high degree of sparking can cause your spark plug to wear out before other parts of your engine (source).

The spark plug also comes in direct contact with the gas before it burns and after the exhaust gets spit out. So, your spark plug can get dirty quickly from all of the fuel and smoke that touches it. 

When the spark plug becomes dirty, it gets covered in a layer of oil and gas. This residue makes the plug greasy, which prevents it from making a spark. So, a dirty spark plug can’t burn fuel, which will prevent the entire engine from starting up. 

How To Prevent Your Weed Wacker Engine From Seizing

While having a weed wacker engine seize mid-use is not uncommon, it is ordinarily easy to fix the issues that cause seizing. 

Most of the time, a seized-up engine means that you don’t have enough fuel or the correct type of fuel. So, if you encounter issues, make sure that your weed wacker has enough gas and that the gas is mixed in an appropriate way to let the engine start.

If you have enough gas and your engine is still seizing, try replacing your air filter. You should also ensure that nothing is obstructing the exhaust. 

If this doesn’t fix the issue, try cleaning off or replacing your spark plug. You can find air filters and spark plugs at most small engine repair shops or online. Likely, after adding gas and cleaning or replacing these parts, your engine will work as well as new!

Final Thoughts

Though engines may seem like incredibly complex devices, they are not so tricky when you break them down piece by piece. While your weed wacker shouldn’t seize regularly, sometimes it does happen. Rather than going out and getting a new weed wacker, try these simple steps to stop your weed wacker from seizing!