When A Lawn Mower Starts Up - Then Dies; What Should You Do?

Written By James
Updated July 24, 2021 by James

When A Lawn Mower Starts Up - Then Dies; What Should You Do?

How To Fix a Lawnmower Which Runs Then Dies

Starting up your lawnmower only to hear the engine die shortly after can be worrying, and leave you wondering what the issue is with your mower and the solution to fixing it.

If your lawnmower is starting up then going dead, this is likely due to either the fuel, carburettor, a bad spark plug or too much oil in your mower. Any of these issues can be reasons for your mower to struggle starting but luckily can be easily remedied too.

So to make things easier for you, we have put together a troubleshooting guide with solutions so as you can determine what the issue is with your mower and how to solve it.

Let's get that mower running again!

Common Reasons As To Why Your Lawnmower Is Starting Then Dies

One of the most common reasons as to why a lawnmower is starting then dying can be due to a blocked or dirty carburettor, however, there are also a couple of other possible reasons that should be explored too if your carburettor is not to blame.

Have we listed them out along with the solutions below.

The Carburettor Has Issues

Before we get on to the other start-up issues that can occur with your mower, let's tackle the most common one first.

A carburettor on your mower is one of the most important components as it is responsible for mixing air and gas within your mower, allowing it to run properly. A clogged or dirty carburettor can stop this process from taking place, causing your mower to die, this often happens when the mowers has not been used and left to sit in storage for a while.

Symptoms of a blocked carb could be your mower starting then dying, black smoke, or using too much fuel, the blockage happens from old fuel.

Your carburettor may also be too loose.


To fix a loose carburettor, you simply need to tighten it. If you suspect that your carb bowl is blocked, then you will need to clean it with a carburettor cleaner to fix the issue, always ensure not to overtighten the bowl when you put it back in place.

The Fuel Has Gone Bad

Next up on our list is the fuel in your mower. Fuel can start to go bad in your mower quickly, and when left for a long time will start to partially evaporate which can cause residue to build-up and block the lawnmower from getting enough fuel during use, causing it to die unexpectedly or even not start at all in some cases.


The good news is, in most cases, this issue is pretty easy to fix and will require you to drain this old fuel out and put new petrol in. We also recommend adding a fuel stabiliser to prevent residue from building up in the future when left in your mower.

There's Too Much Oil

We can all get a little carried away with our mower maintenance sometimes and end up over-filling the oil reservoir of our mower. Some symptoms of this problem are white smoke or start-up issues.


To fix this issue, drain the excess oil and see if it solves your problem, to stop it from happening again you should pour your oil slowly and use a dipstick to measure it out.

You Have a Damaged Spark Plug

A spark plug is essential to starting-up your mower as it makes the spark between the fuel and gas to power the lawnmower on, when this plug becomes damaged or dirty, it can give start-up problems with your lawnmower.

Check the spark plug for any signs of damage or carbon build-up.


Remove the spark plug from your mower and give it a good clean, if it is still not working when you reattach it to your lawnmower then you might have a damaged plug.

In this case, just replace the whole spark plug, doing so should not cost you a lot and save you the hassle of trying to fix it. Spark plugs should be replaced every year anyway.

A Blocked Fuel Cap

One of the less common issues that can stop your mower from running properly is a blocked fuel cap.

You will find a hole within this cap that let's airflow to the fuel tank and move the fuel from the tank to the carburettor.

When this gets stuck, you may find that the fuel in your mower can not reach the engine of the lawnmower, causing it to die or not start.


Remove the fuel cap and clean the air hole with a small wire brush so as the air can pass through freely again. Also never overfill your mower with fuel as this can make the fuel enter through this airhole when it expands from the heat.

The Choke Is Not Working

Flooding can be a common issue caused by a choke, whether it is left on for a few seconds or stuck in the on position, this choke can mean that fuel will flood the combustion chamber of your lawnmower and stop it from producing a spark.


To try and fix the choke problem with your mower, you will have to open it up and let the engine restart itself, you can try pulling your mower to start on a half choke and let some air enter the chamber of your lawnmower.

If none of this is working and you suspect the choke is the cause to blame, take it to a professional who can fix the issue.

How To Maintain Your Lawnmower & Avoid These Issues

We hate to say it, but, most of the issues above tend to be caused by someone not doing regular maintenance on their mower. Tasks such as draining the fuel tank for storage and changing the spark plug are part of caring for your mower and can stop larger problems from occurring.

To help you out, we have listed out some essential maintenance tips to keep your petrol mower in the best shape possible below.

  • Always drain your fuel after using - After a mowing season, it's a good idea to drain any leftover fuel, as your mower will be stored away till next season, and in this timeframe, it's likely the fuel will turn bad. You could also use a fuel stabiliser to prolong the lifespan and avoid having to drain.
  • Clean the mower deck - Now and then, you should clean under your mower's deck with a wire brush and hose to prevent grass clippings and debris building up which could cause rust.
  • Disconnect the spark plug beforehand - When tipping your mower over to clean it and check it, you should always disconnect the spark plug first to avoid any accidental start-ups, make sure you tip the mower with the carburettor and air filter facing upwards.
  • Clean the air filter - We recommend replacing your mowers air filter every year and cleaning it regularly to stop dirt from getting into your lawnmower's engine.
  • Keep your oil levels topped up - It's a good idea to drain old oil now and then and replace it with some fresh oil instead. Always avoid overfilling your mower with oil and use a dipstick to measure the required amount.
  • Check the spark plug - When performing maintenance on your lawnmower you should check the spark plug for any dirt or damage. Never overtighten the spark plug and replace it at least once a year to keep things running smoothly.
  • Sharpen the blades - Sharpening your blades should be done regularly so as it can provide the best cut to your lawn and avoid tearing the grass. Most people recommend you sharpen your lawnmower's blades after 25 hours of use, and you should replace them after 100-200 hours of total use.

Frequently Asked Questions About Why My Lawnmower Is Starting Then Dies

What is the carburettor on my mower?

The carburettor is a component in your mower which mixes the fuel and oxygen and allows it to flow up into your mower's engine.

How quickly does fuel go bad in your lawnmower?

Fuel will start to go 'off' in your lawnmower in as little as just 30 days, meaning you should never store your mower away without draining the tank first or adding some stabiliser.

If my mower is blowing white smoke from excess oil, should I worry?

No, this is the natural response of your mower to the increased amount of oil, you can let the smoke burn out after you have drained some of the excess oil. If the white smoke continues after doing this then you might need to start troubleshooting other reasons.

Final Words

Overall, start-up issues from your mower can be concerning, but are luckily nothing to worry about as long as you can determine what the problem is and fix it with our guide above. If you are ever unsure about fixing certain parts of your mower it's best to take it to a professional, as trying to fix it yourself can do more harm than good!

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My father, and his father before him, and his father; for the past 3 generations, my family have always been into gardening. The green fingers is a gift passed down to me and I thoroughly enjoy it! I also have worked in the manufacturing department for Bosch and DeWalt so I like to think I know a thing or two about tools and such!
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