How to Prime a Lawn Mower without Primer?

This post contains affiliate links. If you click and buy we may make a commission, at no additional charge to you. Please see our disclosure policy for more details.

Is your lawnmower having problems to start? Then you probably need to prime it. 

When you prime lawn mower, you’re ensuring that gas goes into the carburetor and thus to the engine to produce a spark and turn on. Without the priming, there’s no spark and no engine power – so the mower won’t start.

The primer bulb or automatic primer on some mowers tends to stop working overtime, so it is always useful to learn how to turn the machine off without it.

Here, we’re going to teach you exactly that. Whether the primer is broken, inexistent, or clogged, you’ll learn how to turn on the mower without it. Care to learn more? Then take a look below!

What is a Lawn Mower Primer?

Most lawn mowers have a pretty small carburetor when compared to the one in larger vehicles.

Because of that, the carburetor tends to dry up faster. So when the user wants to turn on the mower, the carburetor won’t have a single drop of gas, preventing the machine from even starting, 

The purpose of a primer is to push fresh gas into the carburetor when it is dry to help in the combustion process. That way, the mower can start more effectively.

When the primer doesn’t work, obviously, the mower won’t start. So this part needs to do its job if you want the mower to turn on. 

How do Primers Work?

It’s important to know that there are two types of primers: push bulbs and automatic primers. 

One of the primers works from the outside (bulb), and the other works from the inside (automatic). While they have the same purpose, they work a little differently. 

A bulb primer, for example, is a little piece of rubber on the outside that pushes gas inside. It draws fuel from the tank as it is pushed, sending the fuel directly into the carburetor and the combustion chamber. 

The other type of primer is automatic. This one works more like a vacuum, drawing the fuel as it goes through the carburetor when the machine is on. When the mower turns off, the primer keeps the fuel, so next time the user starts the engine, it can release this fuel into the combustion chamber.

Either way, the whole focus is to push fuel through the carburetor into the combustion chamber. If no fuel flows when trying to start the machine, then the primer is probably defective. 

Why Does a Primer Stop Working?

A primer may fail due to many different reasons. But there are three that stand out and explain most of the problems that may be causing a primer problem:

Cracked Bulb

If it is a bulb primer, then there’s a chance this small piece of rubber is torn, broken, or just cracked. This will prevent it from spraying the fuel into the carburetor, thus keeping the mowing from even starting. 

Clogged Filter

The fuel filter is where the primers take the fuel from. When it is clogged or blocked, there’s no chance for fuel to reach the carburetor. Thus the primer can’t do its job. 

Cold Primer

And lastly, when an automatic primer has been idle for a long time, there’s a high chance it doesn’t have any fuel anymore. In that case, no matter how many times you try to start the mower – it just won’t because there’s no fuel to reach the carburetor. 

It doesn’t matter what problem you’re facing with the primer, there’s no need to buy or rent a new mower. Instead, you can start the mower without the primer. Here, we are going to teach you how. 

Step-by-Step Guide: How to Prime a Lawn Mower without Primer?

Priming the mower without the use of the built-in primer may seem like a crazy idea that won’t work. But it actually does. In fact, expert mechanics do this to test different parts of the mower when it doesn’t work.

What’s the process like? It’s straightforward. Either you try to prime the mower manually or instead spray some starter fluid into the carburetor. Below you’ll learn how it’s done. 

Things to Consider:

Even though this is a relatively easy endeavor, you should still prepare for it. Here are some things to think about:

  • Priming the lawnmower will take anywhere from 5 to 20 minutes, depending on your skill level. If you’re experienced with mowers, then you may not have to spend more than 5 minutes.
  • For this process, you will have to look for starting fluid. It is a combination of fuel-related chemicals that replace fuel when the machine doesn’t prime.
  • This fluid can be somewhat thick, which could cause clogging and airflow restriction. So use it carefully without spraying too much when the time comes.

Items You’ll Need

  • Flat-head / Phillips Screwdriver (Optional)
  • Starter fluid

As you see, there’s not much you need to test the mower primer. So you can get on with priming it up right away. Follow these steps:

1.Prepare the Mower

prime lawn mower

 

First off, you need to prepare the mower for the job. This is mostly about ensuring it has enough fluid, and everything is connected:

  • Start by checking the fuel tank to see if there’s any fuel. Take the cap off and see inside. Refill if necessary. 
  • Proceed by removing the top case/cover of the mower. You should discover the engine carburetor (as the primer bulb is close).
  • Then check that everything, including the fuel line, carburetor, and filters are all connected. A single disconnection may cause the mower not to start.

Once you’ve checked everything and it all seems correct, then you’re ready to prime the machine. 

2. Locate the Primer Bulb

prime a lawn mower

Now you have to locate the primer bulb (if you have this type of mower), close to the carburetor.

  • You will have to look around the engine. The primer is usually located under the carburetor, and it typically has a red or black color.
  • Check that it is not broken or cracked. If it is, then that’s the reason for it not to work. You won’t be able to prime your mower without it. 
  • If it isn’t damaged, then you need to press it three times. This should spray some fuel into the carburetor to aid the combustion process.

 You can now try turning on the mower and see if it works.

3. Pull the Cord (Optional)

prime lawn mower

If the primer wasn’t broken and you pushed it three times, then you should be able to turn the machine on.

  • Pull the throttle lever to the maximum position. Then grab the starter rope and pull it. 
  • The engine may not start at first, but you should start feeling some resistance and how the engine tries to turn on.
  • Now push the throttle to the lowest level and try turning the mower on again by pulling the cord. It should turn on.

If the mower doesn’t turn on, then you may need to prime it manually. 

4. Find the Air Cleaner

After trying the previous steps without getting any response from the mower, then you should proceed to prime it directly with the starter fluid. But first, look for the air cleaner.

  • The air cleaner is usually located on the side of the engine. You should remove the cover off the air cleaner as needed (bolt-on, screws, or retaining clip).
  • Be sure not to be too harsh as to damage the air cleaner or the mower’s engine. 

This will give you the green light to remove it from the engine.

5. Remove the Air Cleaner

prime lawn mower without primer

Most air cleaners block the place where you need to spray the starting fluid. So you should remove the air cleaner to allow the starting fluid to do its job.

  • The air cleaner is usually placed inside a housing. You should take it off the housing as necessary. You may need to use the screwdriver.
  • While taking it off, be sure to memorize precisely where it goes, as you will need to put it back later.

You should have direct access to the air hole where the carburetor bore is located. 

6. Spray Starter Fluid

It’s time to spray the starter fluid into the machine. This is pretty straightforward:

  • Grab the bottle of starter fluid. Then point into the hole where the air cleaner was and spray. That is the air intake. 
  • You should spray a single squirt. Nothing more to prevent any build-up or eventually clog with excess fluid.
  • The starter fluid should go directly into the carburetor bore and into the bowl. 

The mower is now almost ready to make combustion.

7. Reinstall the Air Cleaner

Sure enough, you’ll have to put the air cleaner back for the combustion to happen. 

  • If the air cleaner seems too dirty or old, then you may want to replace it. Otherwise, just clean it. 
  • Proceed by carefully placing it back into the housing. Secure it as necessary. 
  • Be quick to place the cover back on the air cleaner and close everything. This will prevent the fluid from evaporating. 

If you did it swiftly enough, then the mower is ready to turn on.

8. Start the Mower

It is now time to test whether the fluid does the job. You should try turning it on.

  • Start the mower as you would typically do. Grab the pull cord and pull it. Otherwise, use the electric starter.
  • The mower may not start at once. But after 3 to 5 tries, it should start right away. 
  • If the mower doesn’t start even after several tries, repeat spraying one last squirt of fluid into the carburetor bore. Then repeat starting the mower once again.

Once the mower starts after spraying the starter fluid, then you’ve successfully primed it without the primer. 

Prime your Lawn Mower without a Primer Now!

To prime lawn mower without a primer may seem like a confusing endeavor at first. But with enough care and attention, you can start your mower even if the primer is broken or just defective.

Remember to follow this guide to the letter and consider every piece of advice. That will prevent you from damaging the mower, but most importantly, it will help you start your mower even without the primer.

So don’t hesitate and try our tips if your mower doesn’t want to prime. 

 

Leave a Comment