What exactly does it mean to prime a lawn mower, and why is it important? Well, priming a lawn mower is one of the operations you perform before starting your mower. Priming is important because it injects fuel into the carburetor when it is empty of fuel. This is an automatic process for some lawnmowers, but others have manual primers. Let’s go over how to prime a lawn mower the right way.
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Is it Important to Prime a Lawn Mower?
Most lawn mowers have a manual or built-in automatic inertia primer. Priming the mower means adding fuel to an empty carburetor. This is important because your engine won’t be able to ignite if the carburetor lacks fuel, and can make it difficult to cold-start your mower. Because carburetors aren’t sealed, the fuel eventually evaporates, especially if it’s sat unused for a while. So, if you don’t prime the carburetor before pulling the starter cord, you won’t be able to start your lawn mower.
When the engine is running, fuel is fed to the carburetor by the fuel pump. But the fuel pump can only operate when the lawn mower creates pressure. When the mower is off, there is no pressure, and no fuel gets pumped into the carburetor. Any remaining fuel will slowly evaporate. The primer’s job is to create momentary pressure to pull gasoline through the fuel system and into the carburetor when the engine is off. So, the only way to start an engine with a dry carburetor is to prime it first.
How to Prime Your Lawn Mower
If your mower has a built-in automatic primer, then it does the priming job for you. However, if your mower has a manual primer bulb, you must follow a 3-step starting process to get your engine started. Let’s check it out.
Find the Primer Bulb
Primers don’t all look the same, but they are always near the carburetor. Primer buttons are normally made of clear plastic. You’ll either find it on the carburetor or on a fuel line connected to the carburetor.
Press the Primer Bulb
After finding the primer bulb, press it firmly three times. This should be enough to get enough fuel into the carburetor to start your engine.
Start the Lawn Mower
Now that you’ve primed the carburetor, you can go ahead and start your lawn mower. Your lawn mower should start after a couple of pulls.
Priming Mistakes to Avoid
I know that priming your lawn mower sounds very straightforward, but there are two ways that you can get it wrong.
Not Priming Enough
Your engine needs enough fuel to start. So, if you don’t prime it enough, then it won’t pull enough fuel. You’ll know you haven’t primed your engine enough if it doesn’t start with a couple of pulls of the starter cord. Press the primer bulb one more time and try starting your lawn mower.
Priming too Much
It’s possible to flood your engine by adding too much oil to the carburetor. Priming too much will cause the excess fuel to soak the spark plug. A wet spark plug won’t ignite. Leave the lawn mower alone for around 10-20 minutes, and wait for the fuel to evaporate and for the spark plug to dry. Then, try to start your lawn mower without priming it. If your mower doesn’t turn on, then prime it again, making sure to only press the primer button a couple of times.
