August 15, 2021
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  • My Lawn Mower Starts Then Dies: How Do I Fix It?

Lawn mower repair can be a simple fix or a complex undertaking, depending on the type of engine. A gas engine has both ignition and carburetor that need to work in order for it to run. If your lawn mower starts then dies, you're going to want to check these 3 things first! 

If your Lawn Mower Starts Then Dies

My Lawn Mower Starts Then Dies: How Do I Fix It?

If your lawn mower is sputtering, or your lawn mower won’t start after sitting out, you may have another issue, but if your lawnmower starts then dies, you may have one of three types of problems:  dirty air filter, clogged air filter, or bad fuel.

The most likely reason for your lawn mower to start and then die is bad fuel, which occurs when gasoline gets old (it goes bad over time), or if you put in the wrong type of fuel.

Check that you are putting in fresh fuel that isn't more than 30 days old. The second likely cause of starting and then dying is if you have a clogged air filter because, without a good supply of oxygen being delivered to the spark plugs, your lawnmower will literally run out of "gas" before it can turn over.

Finally, the third and least likely reason for your lawn mower to start and then die is that you have a dirty air filter.

If your lawnmower was running fine before it died, you probably just need to replace the fuel filter (if it's clogged), or clean or replace the air filter.

Let's look at the bad fuel option first, two first, then we'll cover the other options down below!

Bad Fuel

Sputtering Lawn Mower

First, check the fuel level within the tank: you'll need to make sure that it's not empty before moving on.

If there is still no response from your lawnmower after checking the fuel supply, try priming it a couple of times by turning over the engine while simultaneously pumping the primer bulb located on top of the gas tank.

This will force more gasoline into the carburetor so it can mix with air and ignite more easily. Give it a few seconds before trying to start again; if nothing happens, repeat this step until you get positive results.

On some engines, you might have to remove the gas cap and crank for several seconds with fumes escaping in order to activate this feature (this applies mainly to small-engine grass trimmers).

If your engine still won't start, check the choke feature on the carburetor (you might be tempted to try and turn it, but don't do that!) as this is a common way to fix a "stale" fuel problem.

If you're using an old-fashioned pull starter instead of a rope, then I suggest you look into replacing yours with a modern electric starter or battery option. They'll save your arm from being worn out by constant cranking! And if the lawnmower doesn't have enough power to go faster than about 10mph, then make sure you've properly lubricated all moving parts within the engine.

Dirty Air Filter or Blocked Fuel Line

Dirty Lawn Mower Air Filter

Step 1 – Remove the Air Filter Cover:

The first step is often overlooked yet it's important because dirt might build up on the throttle control lever; this could prevent proper operation.

These engines operate by sucking air through a set of filters (also called an "air cleaner") either directly into the cylinders ("direct" air filter) or into a separate intake manifold ("indirect" air filter). The air cleaner removes dirt and debris that could clog the carburetor.

The next step is to remove the air filter cover (or in some cases, the whole air filter housing) so you can easily access the inside of the engine.

Step 2 – Remove Air Filter:

If you have an aftermarket filter, simply unscrew it from your lawn mower's engine by turning counter-clockwise.

A paper or foam element will be secured in place with a metal cage or frame; this is usually tightened using wing nuts mounted to each end of the frame.

Lift off one end, then slide out the element. For most foam filters, you'll need to blow them clean before reinstalling.

Step 3 – Clean Air Filter:

Look inside the filter compartment and you should see a foam element or paper filter. Either one will work, but paper filters are more popular — in fact, they're required if your engine is certified as meeting California emissions standards.

Paper filters can be cleaned using a garden hose or a pressure washer; scrub off any stubborn dirt with soapy water and then rinse thoroughly before installing back into your lawnmower.

Foam elements can be rinsed under cool running water, although some people prefer to simply replace those every few months rather than wash them weekly (however, this might not apply if you have animals like dogs that could track mud onto your lawn).

Step 4 – Re-Install Air Filter:

Once your air filter is clean, reinstall it into the compartment in the reverse order you took it out. A foam element should be secured using either wing nuts or metal clips; a paper filter will only need to be slid back inside the container.

Note: If you have a Briggs and Stratton engine, then your first step is to remove the carburetor cover rather than an air filter housing. For Briggs engines (but not for Honda or Tecumseh), there's also an additional shield on top of the carburetor that you need to lift off before removing anything else. You can find instructions for replacing fuel filters here.  If you're dealing with a Honda engine, then your air filter should be easy to remove.  To get it out, you have to unscrew the two wing-nuts holding the element in place and pull it out of its housing (you don't need to turn it upside down).

Step 5 – Replace Fuel Filter:

For most gas engines, a clogged fuel line or filter will result in an engine that won't start at all.  The first step is to determine if there's adequate fuel supply; check the fuel level within the tank and make sure the float arm isn't stuck or blocked by debris. If there's still no response when you try starting it, look for any signs of kinked or broken hoses. A common problem with string trimmers or leaf blowers is a blocked gas filter — if your fuel line becomes blocked, then it's possible for dirt to enter the engine, which can prevent an engine from starting properly.

It might take a little time to figure out exactly what's wrong with your mower – don't get frustrated! There are lots of things that can go wrong with gas-powered engines (not just lawnmowers), so it'll help to familiarize yourself with the basic diagnostic process. And of course, you should check how frequently you're supposed to change your air or fuel filters.

Dirty Spark Plugs

Dirty Spark Plugs

If you don't have a gas-powered lawnmower, but rather an electric model or that old-fashioned pull starter, then your problem could be with the spark plug.

And if you're using an electric cord... wait, those are supposed to give you power for free! Okay, I'll stop and just say that ensure your extension cord is properly grounded and in good condition. If it's frayed or damaged, replace it immediately (or take the time to repair it!). Otherwise, check the following:

  • Check the spark plug housing for cracks or signs of wear; if there are any such defects they will need to be replaced.
  • Or on some models, you might simply need to clean off bits of gunk.
  • Be sure to use only a small amount of gasoline and never use any kind of flammable cleaning solvent on the plug itself.

If you can see that the spark is showing but there's still no response from the engine, then look at your extension cord (if your electric mower isn't battery-powered) or check to make sure it hasn't frayed and is in good condition.

And if all else fails, it's time to consider replacing the spark plug; once again, be careful not to touch it with anything other than the equipment designed specifically for that purpose!

In Closing

Correct mower maintenance will help the engine run smoothly and last longer, so keep those tips in mind for future reference!

And if your lawnmower engine won't start at all, then you'll need to go through this entire process before trying again - taking care of all of the problems identified above - so try to figure out what's wrong with it first, okay?

Good luck; I hope this article has been helpful!

If anything is unclear let me know- I'll try to clear things up as soon as possible.

Daniel Simmons

About the author brings my 25 years experience as a professional gardener and landscaper to you!

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