Lawn Mower Starts Then Dies

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Experiencing a situation where your lawn mower starts then dies before you can even get that lawn looking tidy and healthy? I have too and I can say it’s a very frustrating ordeal.

This led to research about what exactly was wrong with my lawnmower, why it was happening and what I could do to make it all better. Read along to learn how to fix yours yourself.

Caring for your lawnmower is just as important as caring for your lawn since they both affect each other. Without a good lawn mower, maintaining your yard might become difficult and impossible to do properly.

In this post, you will learn why your lawn mower could be starting and dying and what you need to do to avoid unnecessary stress or panic.

What Causes A Lawn Mower To Start Then Die?

There could be a variety of things wrong with your lawn mower causing it to start and die.

Finding out which of them is the problem is where the bulk of work is.

Here’s a list of some of them so you can check and figure out what is wrong:

Dirty Carburetor 

This is usually the first thing to consider when you notice that your lawnmower starts and immediately dies.

Whether you live somewhere where your mower is never used during the winter or you live in a temperate zone where the weather is warm all year round and the mower is used throughout the year, your carburettor still needs to be cleaned regularly.

Why is a Clean Carburetor Important?

A steady flow of gasoline is needed by the engine of your mower to run properly. 

The carburettor works to mix the gasoline with just the right amount of oxygen needed to create combustion. 

The combustion now makes the crankshaft rotate continuously which is the principle that makes the lawnmower work effectively. 

A dirty carburettor compromises the process above making it impossible to get the right effect and causing the engine to start up and die almost immediately. 

How To Fix A Dirty Carburetor

To get your carburettor cleaned out effectively, you may need to get a can of aerosol carburettor cleaner.

This should cost about $10 or less and will last for a season or two if properly maximized.

To clean your carburettor, unscrew the carburettor bowl and spray around it once with the aerosol cleaner.

Ensure to clean the crew and hole with the cleaner as well and this is where a key spray applicator comes in handy as a precise application is needed. 

Ensure that when you are reattaching the bowl, you do not over-tighten the screw as this could strip the threads enough to distort the seal.

Maintenance Tips For A Healthy Carburetor

  • Before you start up your mower, lightly spray the aerosol cleaner near the air intake hole of your mower’s engine.

    The air intake hole is usually located just behind the air filter. Remove the filter, spray the hole then reattach the filter. 

    After doing this, you can then start the mower.
  • Spray your mower’s carburettor every time you mow and this should be done right before you pull the plug. 

    I do this and I recommend you do the same to prevent the accumulation of dirt.

Stale/Dirty Gas

A gas lawnmower cannot run without gas but the quality of gas you use is also an important factor that determines how smoothly the mower runs.

If your mower has been inactive for a while with gas in it, then it has likely evaporated and left behind residue that is damaging to your mower engine.

This residue clogs the internal parts of your mower leaving particles behind and resulting in restricted gas flow that causes the mower to start and die soon after or not start at all.

How To Fix This Issue

If there’s old gas in your mower that isn’t up to the halfway mark, you can top it up with new gas. This could help to dilute the impurities in the old gas, reducing its effect on your engine.

However, if the old gas in the tank is about half the tank or more than half, your best option is to siphon it out and fill the tank with fresh gasoline.

To make everything better, you can also add a stabilizer that works to dilute any clogging residues. It is cost-efficient and saves you from any future trouble.

Faulty Choke

The job of the choke in the lawnmower is to help cold start the engine. When the choke is being held on to, it increases the fuel supply to the engine in those moments which in turn helps to start the cold engine. 

After the engine has warmed up a bit, you can then turn off the choke to allow the engine to run on a regular operating fuel mixture. 

A faulty choke makes it difficult to start the engine and also hinders the engine’s proper fuel mixture supply. 

How To Fix A Loose Choke 

If you find out the choke of your lawnmower is loose or the spring is not pulling back to its closed position, all the loose screws need to be tightened properly or the spring needs to be replaced.

Dirty Spark Plugs

The job of the spark plug is to ignite the air and fuel mixture in your engine. The spark/small explosion created by the spark plug makes your engine produce power.

The spark plug is an important component of your mower’s ignition system. If the plugs are dirty or faulty then they will not spark which means your mower will not start at all or it will start then die immediately.

How To Fix Dirty Spark Plug

Your spark plug can be found covered with a black cable in front of your mower.

You’ll need a socket wrench of the right size to remove the plug.

If the spark plug isn’t too dirty, you could try cleaning with a wire brush but if the plug looks too dirty or has a car in residue, you may consider changing the spark plug entirely.

A new spark plug would cost between $8-$10 and you can find the right size for your mower around.

Spark Plug Maintenance 

You should make sure to replace your spark plug every one or two years, preferably every year.

This helps to ensure that your lawnmower runs efficiently. Regular cleaning also helps to prevent buildup.

How To Replace Your Spark Plug

To remove your spark plug, all you need to do is simply unhook the spark plug wire and remove the old plug with a spark plug socket.

Replacing your spark plug is easy but can be a bit challenging on the first try.

First, you need to use a spark plug gauge to measure the gap between the two electrodes at the top of your spark plug. 

Then, you need to check for the specifications for your lawn mower model to know the right size of the gap.  

The next step is to install the new plug and attach the spark plug lead. Also, make sure that you do not overtighten when installing. 

Dirty or Clogged Air Filter 

When your air filter is either clogged or dirty, then the airflow needed to mix with fuel is obstructed. 

Poor airflow makes the engine of the lawnmower die within a few minutes after you start it. Due to the kind of work the mower does, it usually catches dirt and debris from the yard and causes the filter to get clogged quickly.

How To Fix A Clogged or Dirty Air Filter

A sturdy porous material is used to make air filters which makes it easy to clean using compressed air. 

If it is extremely dirty, you can use lukewarm water and soap to wash it carefully then dry it off with air by leaving it outdoors for a while. 

Maintenance Of Air Filter

Most lawn mower manufacturers recommended a once-in-a-year cleaning once a year. 

You should also purchase a new one if you notice a tear in the current one or if it has completely worn out. 

Also, you should never turn on your lawn mower without an air filter. It protects the dirt and debris you would be working with from entering directly into the machine. 

When dirt enters the engine, it may cause damage to the valves, piston, and cylinder walls. It could also completely damage the lawnmower and you will have to invest in another one.

Too Much Oil In The Mower’s Reservoir 

If you have checked your carburettor and it is completely clean and the spark plugs are firing properly, the problem may be too much oil.

While overfilling the mower’s reservoir with oil may seem like a great idea, it isn’t.

How To Know Excess Oil Is The Problem

When your mower is emitting white smoke, then this is a telltale sign that there is excessive oil in the mower. 

While the mower may still keep working, it won’t last long and the excess oil will eventually drown out the engine thereby causing it to die.

How To Fix The Issue Of Excess Oil In The Reservoir 

This is an easy issue to fix since all you need to do is drain out the excess oil.

You can use a siphon to do this or you can tip your mower forward from behind if it’s a walk-behind mower. After draining the oil you should start the mower again to check the smoke. If it no longer emits smoke, then you are good to go.

How To Prevent Excess Oil In The Reservoir 

I believe everyone including me is guilty of sometimes overflowing the oil tank. 

So far, I have learnt to go as slow as I possibly can when filling the tank with oil and this has helped me reduce the risk of overflowing the tank.

If you have overfilled your tank, you can use a dipstick to measure the quantity of oil before draining and also do the same after to ensure that it is on the right level.

Not enough oil is also another problem and may even be more serious than excess oil which is why a dipstick is needed. 

Other issues that could cause your lawn mower to start and die are listed below:

  • Gas tank Blockage
  • Worn Out Carburetor 
  • Moisture in the Fuel line and Gas tank
  • Blocked Muffler

When To Hire A Professional 

If you have tried all that you can to fix the issue but it persists then you should call a professional. 

Some of the issues are a bit complex and if you’re not the do-it-yourself type, then you may require a professional to do the work. 

This ensures you’re not doing the wrong thing that could even worsen the state of your lawnmower

However, if your mower is still covered by warranty, you’re in luck! You should contact the manufacturer to help you locate the designated services centre in your area. 

But if you are no longer covered by warranty, then you should contact a local repair shop to help with the issue.