Priming a lawn mower can be a bit intimidating for first-time lawn mower owners, especially when they haven’t encountered this before.

Guide to Priming Your Lawn Mower

In this complete guide, we’ll discuss how to prime your lawn mower, its importance, and other related details.

How To Manually Prime Your Lawn Mower?

To manually prime your lawn mower, simply add fuel to the carburetor of the mower when there is no fuel. Some lawn mowers do this process automatically while others do not. A manual mower primer requires more attention due to the dedicated primer found on the carburetor.

Just by the term alone, priming the lawnmower should be the first thing to do when cutting grass. Here are the steps in priming your lawn mower:

– Find the Primer Bulb

Manual primers can vary in design, but they all have one factor in common: they are found on and near the carburetor. Manual primer bulbs are usually identified as clear rubber buttons that are attached directly to the carburetor. Sometimes, manual primers are also attached to a short fuel line that connects to the carburetor.

How to Prime Your Lawn Mower

Priming small engines is always important, especially the ones found in most lawnmowers. The carburetors found in the engines are not sealed, which allows fuel to evaporate after some time and leaves the part dry.

Left in this condition, the carburetor will not function optimally. Even when the starter is pulled forcibly and repeatedly, the lawnmower’s engine won’t start. The carburetor needs fuel to ignite, and without it being primed, there is no pressure for it to pull fuel.

To resolve this, lawnmower manufacturers usually place a primer bulb as a manual solution to add fuel to the carburetor. Other models have an automatic internal inertia primer that works to power the engine by keeping some fuel inside.

When the manual primer bulb is pressed, fuel is driven to the carburetor. This process works by sucking the fuel through the gasoline system. Generally, lawnmowers use fuel pumps that rely on the pressure created by the engine of the lawnmower. When the engine doesn’t start, then there will be no pressure.

– Prime Manually

After locating your lawn mower primer, give it a firm but gentle push. Some people recommend two pushes while others suggest four. However, the most optimal number of pushes is three. Most homeowners would agree that three pushes to the primer bulb will give it enough starter fluid to feed the carburetor.

– Power the Engine

Once you have primed the carburetor by pushing the lawnmower primer bulb three times, you can start your lawn mower.

Get Your Lawn Mower Ready in No Time

Pull on the starter once or twice, and your mower should begin to start up.

How To Avoid Mistakes?

To avoid mistakes when priming your lawnmower, make sure to add enough fuel to the carburetor and don’t push the primer bulb too many times. Even if the priming process is so simple, it can still be quite easy to make mistakes and get the whole method wrong. 

Priming a lawn mower does not require much thought or effort, but it does require knowledge. Let’s look at two possible mistakes that can be easily avoided.

– Under-Priming Your Lawnmower

There is a possibility that the carburetor will not be primed optimally. This means that not enough fuel has been injected into the carburetor. Most likely, you have pushed the primer bulb once or twice only.

Achieving Flawless Lawn Care

When this happens, the lawnmower will have problems starting up, similar to when left unprimed. You can easily diagnose this problem when the engine does not start despite pulling on the starter cord several times. If it is very hard to pull the lawn mower’s cord the causes might be different but there are some easy solutions.

To remedy this, simply push the primer bulb one more time. Once you do this, try starting the engine again. If enough fuel has been injected into the carburetor by the last push of the primer bulb, your engine should start without issues.

– Over-Priming Your Lawnmower

Over-priming can happen when the primer bulb is pushed too many times. This can result in the engines of your lawnmower becoming flooded by fuel. The fuel can spread into the combustion chamber, where it can gather and pool. Under this condition, the spark plug can get too wet and will not ignite. You can either wait for it to dry or you can locate the spark plug and dry it manually.

If you find that you have pushed the primer bulb more than necessary, don’t worry. Even if the engine fails to start, you can still solve this issue. Simply leave the lawnmower alone for about 10 to 20 minutes. The excess fuel will evaporate during this time, allowing the parts of your mower engine to dry out slightly.

Once the time has passed, start your lawnmower once again. This time, do not prime it. If your engine does not start, it might have evaporated the fuel too much. To correct this, start the priming process all over again but this time with just three pushes to the primer bulb.

How To Diagnose Why Lawnmower Primers Stop Working?

To diagnose why lawnmower primers stop working, you will have to figure out if it is because of a cracked primer bulb, a clogged fuel filter, or a cold primer. There are many reasons that can cause this condition, but these three are the most common.

Sometimes, the primer bulb of the lawnmower’s engine can stop working. The top three causes are found below.

– Cracked Primer Bulb

The rubber button can become damaged due different such factors as age, environmental exposure, or just wear and tear. As a result, the primer bulb can end up cracked, broken, or torn.

The damaged bulb will be unable to inject fuel into the carburetor’s combustion chamber. Consequently, the mower will have issues starting up. To resolve this, replace your primer bulb that has shown clear signs of damage.

– Clogged Fuel Filter

The primer bulb takes gasoline from the fuel filter into the carburetor. However, when the fuel filter is blocked or clogged, it can be difficult for the primer bulb to access the fuel. You might as well check and clean the air filter while doing this check.

Essential Guide to Priming Your Mower

This can result in the engine not starting due to the lack of fuel or starter fluid in the combustion chamber of the carburetor. To remedy this situation, either clean or replace the clogged fuel filter. Once this is done, try starting the engine of your riding lawn mower to see if it worked.

– Cold Primer

This usually affects automatic primers that have been idle for extended periods of time. The lack of activity can cause fuel to evaporate fully. The clearest sign of this situation is the inability of the engine to start because the combustion chamber does not have any fuel in it.

You can try cleaning the air filter and the fuel filter to keep everything in tip-top shape. Additionally, spraying the carburetor cleaner onto the part directly can help prime the automatic primer once more.


It is essential that homeowners learn to prime their lawnmowers in order to keep them in their prime condition.

For you to do the same, let’s recap what we’ve explored so far:

  • To prime the lawn mower manually, simply push the primer bulb three times.
  • If you have accidentally under-primed or over-primed, the lawnmower will not start and will still need to get primed again.
  • It is important to check the mower primer button or bulb for damages, which can interrupt the fuel injection to the carburetor.
  • Always check the air filter and the fuel filter for blockages and replace them when necessary.
  • For lawnmowers with automatic primers, ensure that the carburetor paths are clear and suitably primed.

Knowing how to prime your lawnmower is an essential skill, especially during the warm spring and summer months. Share your success stories with us by leaving us a comment or two!

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