Skip to Content

Lawnmower Won’t Stay Running: You Will Find a Solution Here

So, your lawnmower keeps dying on you. Well, just like anything with a motor, sometimes your mower will have issues that cause it to stall and cut off. If you are having that issue with your mower, then you are in the right place. In this article, we will look at the reasons why your mower won’t stay running and also give you the solutions for them. Keep reading to see all the possible reasons why your lawnmower is stalling.

LawnMower Won't Stay Running

Ahhh…the smell of fresh-cut grass. There’s really nothing like it. However, it’s pretty frustrating to be all ready to tackle those tall green blades only to have your mower fire up and then sputter out.

If your lawn mower starts then dies, you want a quick answer about what’s to blame, and what to do to fix it. I’ll share the 4 most common causes to this mower problem and what you need to do to address each.

When your mower starts then dies it can feel like you’re alone, but this problem is more common than you might think, and the fix can be an easy one.

Let’s take a look at the four most common reasons behind that false start and how to fix them. We have highlighted some major Causes for Lawn Mower Starting then Dying

If your lawnmower starts, runs briefly, then dies these are the four most common reasons that’s happening:

1. Dirty Carburetor in Lawn Mower

When your lawnmower starts then dies, your carburetor is most likely involved somehow. Think about it. If you live in a northern region, your mower sits all winter … waiting months without any action.

LawnMower Won't Stay Running

And, if you live in a more temperate zone, your mower works hard year-round. In both cases, your carburetor is going to need a little TLC.

What’s so Important about the Carburetor?

Your engine needs a steady flow of gasoline to run correctly. The carburetor is responsible for mixing gas with just the right amount of oxygen to create combustion.

This combustion supplies a continuous rotation of the crankshaft that is necessary to run the mower’s engine.

If your carburetor is dirty or the carburetor bowl is clogged, the process above is compromised, and your engine may start up, but it will not run properly and may die shortly after you pull the cord.

How Do I Fix it?

Your dirty carburetor needs a good blowout with an aerosol can of carburetor cleaner. This will cost you less than $10 and will last for a season or two.

I use the WD-40 Specialist Fast-Acting Carb/Throttle Body Parts Cleaner (Amazon link). This cleaner uses a solvent formula to breakdown carbon contaminants, leaving your carburetor clean and gum-free.

I give my mower a shot of that every time a mow, right before pulling the cord, and recommend that you do the same.

LawnMower Won't Stay Running

The only drawback to this particular cleaner is it does not have a straw for targeted spraying. If you need a more precise application, Gumout makes a cleaner (Amazon link) that will do the trick with its jet spray applicator.

Now for the Process

Unscrew the carburetor bowl and give it a once over with the cleaner. Be sure to clean the screw and hole with the carburetor cleaner as well. This is where the directional spraying straw is particularly handy. When reattaching the bowl, don’t over-tighten the screw. This could strip the threads enough to distort the seal.

2. Old Gasoline in Your Lawn Mower

You know your mower can’t run without gasoline, but the quality of the gas is equally important. If the gas in your mower has been sitting inactive for a while, evaporation has most likely created a damaging residue.

This residue leaves particles that clog your mower’s internal parts.The end result is restricted gas flow, which means your mower can start and die shortly thereafter. Sometimes, your mower won’t start at all.

How do I fix it?

If your mower tank is less than half full of old gas, you might try adding new gas to dilute the impurities. If the old gas is more than half of a tank, it would be best to siphon it out and fill the tank with fresh gasoline.

In both cases, adding a stabilizer such as Sta-bil Fuel System Stabilizer (Amazon link) is a smart idea.

 Stabilizers prevent clogging residue for up to two years, and at around $10 a bottle, they are an inexpensive additive that can keep your mower running like a champ. Always read the directions to know the proper fuel-to-stabilizer ratio for your mower.

You can buy it online, or locally at Home Depot or some local hardware stores.

3. Dirty or Defective Spark Plugs

Spark plugs supply the “spark” that ignites the air/fuel mixture in your engine. This small explosion makes your engine produce power.

The spark plugs are an essential component of your mower’s ignition system. If they are dirty or faulty, they will not spark, and your mower will not start, or may start and then quickly die.

How Do I fix it?

Your mower’s spark plug(s) are easy to find. In most walk-behind mowers they’re covered with a black cable and right in the front of your mower.

You’ll need a socket wrench of the right size to remove your plug (check your manual to find the correct size for your mower/spark plug).

If your spark plugs are not too heavily coated with build-up, you can try cleaning them. You should never clean a spark plug with a shot-blasting cleaner. A wire brush and appropriate cleaner will do the trick if the plug is just dirty.

However, if your mower’s spark plug looks filthy or appears to have a dark carbon residue, you might be better off replacing.

This is an easy job and it’s inexpensive – a new spark plug with be $8-9 and your size is probably available locally.

4. Too Much Oil in the Lawn Mower’s Reservoir

If your carburetor is clean and the spark plugs are firing, the problem might be too much oil.

I believe it’s human nature to want to over-fill a lawn mower’s oil reservoir, especially if you’re not particularly handy. You feel so accomplished that we’re doing the job yourself that you go overboard and over-fill the tank.

It happens, and it’s not the end of the world (or your mower). White smoke coming out of the engine is a tell-tale sign that excessive oil is the culprit.

If a lot of smoke is coming out, your mower might be running, but not for long. In this case, the excess oil will eventually drown out the engine and cause it to die.

How Do I Fix it?

This is actually an easy fix. If you have too much oil, you just need to drain some. You can use a siphon, or (if you have a walk-behind mower) you can tip your mower and drain the oil from the hole where you add it.

Not enough oil is another (and more serious) problem, and you would not want to inadvertently trade one issue for another.

After draining some oil and checking to see if you have an adequate amount, start the mower again. If the mower fires and stays running without the billowing puffs of white smoke, you have corrected your problem.

Lawn Mower Starts Then Dies: When it’s Time to Call a Professional

LawnMower Won't Stay Running

If you have tested all of the methods I’ve shared for fixing your lawn mower that starts and then dies, hopefully your problem is solved.

But if not, it might be time to throw in the shop towel and call a professional. The following are other issues that could be keeping your mower from running properly.


More Reasons Your Lawnmower Starts then Dies

  1. Worn-out carburetor:  If your carburetor is more than dirty, it might be time to replace it.
  2. Faulty chokeUnless you are extremely handy, identifying this problem and restoring the delicate balance necessary to get your engine purring like a kitten is another issue for the experts.
  3. Gas tank or gas line blockage: Anytime your gasoline is not getting to the engine, your mower will not run properly. A blockage of any kind that prevents the constant flow of gas is a problem that might take a trained eye to identify and fix.
LawnMower Won't Stay Running

The average weekend warrior with limited knowledge on the matter will probably feel more comfortable hiring someone with the experience and the tools to get the job done right.

I recommend that you start by checking your mower’s warranty. If it’s covered, a repair may not cost you anything. Some companies will send someone right to your home, or come to pick up your mower to save you time.

To summarize those here, however:

  • Clean your air filter regularly (replace it annually).
  • Change your spark plugs every 1-2 years.
  • Keep stored oil and gasoline clean. Use a stabilizer in your gas to keep it fresh for up to two years, or pay extra for 4-cycle TruFuel.
  • Keep your engine clean with an engine degreaser.
  • Use the dipstick and don’t overfill your oil reservoir.
  • Keep your carburetor clean with a carburetor cleaner spray.

Performing regular maintenance on your mower is the best way to keep it running smoothly, and investing a few bucks per year in this is worth it.

You’ll avoid headaches, repair costs, and your mower will last a long time, starting right up when you need it. If you do encounter a problem with your lawnmower, decide if you are comfortable with trying to fix it yourself.

If the issue seems to be something beyond the basics, don’t hesitate to call a professional. There’s no shame in this, and sometimes do-it-yourself repairs are just not worth the time, energy, or frustration.

But if you are up for the challenge of fixing the problem yourself, the above guidelines provide a good starting place, and online videos may also be useful. I think YouTube is a great resource.

LawnMower Won't Stay Running

The main thing is that you get your mower fixed so you can get out there and make your lawn the envy of the neighborhood.

Frequently Asked Questions

Are lawn mowers dangerous?

Ans: Any device that is not utilized properly in the way that it is intended can be potentially dangerous. Generally, though, lawnmowers pose the risk of as much danger as a kitchen knife would.

When using lawnmowers, however, several safety measures have to be observed when using a lawnmower, especially an electric lawnmower.

What safety measures should I observe when using lawn mowers?

Ans: Chief among the safety measures to be put in place when using a lawnmower is the fact that the lawnmower should only be used for the sole purpose for which it is intended.

Electric lawn mowers, especially corded ones, should never, under any circumstances be used in the rain. Mowing should also be done in the opposite direction of the cord, to avoid accidentally mowing the electric cord with the grass.

Why does my lawn mower not start?

Ans: Depending on the type of lawnmower you use; a lot of factors may be responsible for your lawn mower not starting. A gas-powered lawn mower may be out of gas, have a weak battery or be short on oil. A corded electric lawn mower may have a bad connection to the electric socket, or the extension cord may be out of order.

 A self-propelled lawn mower may have a faulty recoil cord; and cordless electric lawn mower may have a bad battery or a poor connection between the motor and the lawn mower. If the issues are such that you cannot fix them by yourself, employ the services of a professional.