How To Change A Spark Plug On A Lawn Mower

How To Change A Spark Plug On A Lawn Mower

What To Do When Changing Your Spark Plug

Disconnect the lawn mower’s spark plug cap

How to a change spark plug on a lawn mower Clean the surrounding area where the spark plug is seated to remove dirt that may fall when you unscrew the spark plug.

Use a ratchet with a deep socket in unscrewing the plug.

Only use the right socket size to avoid breaking the porcelain part of the spark plug.

If the spark plug cannot be unscrewed

Don’t force it. Spray its base with a penetrating lubricant and let the liquid settle inside the spark plug chamber for about 10 minutes.

Whenever you take out the spark plug, check its electrode for any liquid, corrosion, carbon deposits or gasoline.

Clean the spark plug thoroughly. If the spark plug is old and faulty, change it altogether.

With the spark plug chamber and the spark plug is cleaned out, check the electrode  gap and screw it back when everything is checked.

Recap the ground cap and test the machine by starting it. If the machine doesn’t start, the problem could be due to other factors.

How To Change A Spark Plug On A Lawn Mower
How To Change A Spark Plug On A Lawn Mower

Why Do I Need To Change My Lawn Mowers Spark Plug

 You now know how to change a spark plug on a lawn mower and save money on servicing.

Let’s explain what your spark plug does  

All internal combustion engines need electricity to ignite air and gas mixture in order to create combustion.

On lawn mowers, the function of the spark plug is to produce a spark at the right time to ignite a combustible mixture of air and gas in the combustion chamber.

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This combustion forces the pistons to rapidly work in pumping action and enables the crankshaft to rotate and this is how significant the role of the spark plugs in every lawn mower.

But do you know how to change a spark on a lawn mower when you need to?

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If you look at the spark plug, you can see that this is just a small  device that looks quite simple.

But did you know that in spite of its size it is composed of elements that can do wonders in converting gas into power to cut your grass?

Let’s look first on what a spark plug is made of before we discuss the simple rules on how to recognize a faulty spark plug and how to replace it.

Knowing all its parts, this will let you understand why you need to know

How to change a spark plug on a lawn mower and have regular cleaning or replacing your mower’s spark plug in order to keep your lawn mower running well.

From the outside, the spark plug has a metal rod and steel shell while most of its base is protected by porcelain.

This porcelain or ceramics protects the internal parts of the spark plug as the engine gets very hot.

It can also prevent high voltage from escaping when electricity flows from the electrodes.

There are two important electrodes in a spark plug and these are the central electrode and the ground electrode.

Both are made of nickel alloy which enables them to withstand high temperature.

How To Change A Spark Plug On A Lawn Mower
How To Change A Spark Plug On A Lawn Mower

The central electrode which is at the base part of the spark plug is responsible for carrying high tension current

While the ground electrode serves as the ground and is attached to the cylinder head of the engine.

Between these two electrodes is the gapwhere the spark happens.

How To Change A Spark Plug On A Lawn Mower

When a high voltage current flows to the central electrode, the mixture of gas and air that is present between the electrode gaps explodes and produces a spark.

This spark produces combustion inside the combustion chamber and this is the beginning of firing up the engine.

However, spark plugs can also develop problems on their own as we discuss them below.

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Problems That Occur with lawn mower Spark Plugs

Cracking of porcelain protector.

When there is a constant bombardment of high thermal stress that occurs between the electrodes, in the long run, this may eventually crack the porcelain protecting the electrodes.

This usually happens if you have a low-quality type of spark plug.

If you know how to change a spark plug on a lawnmower, replace the spark plug for a new one but make sure you buy only the reliable brand to avoid future cracking problems.

Carbon deposits.

Due to constant ignition between the electrodes, a carbon build-up will be most likely to form.

Clean the spark plug by spraying carburetor cleaner or replace the spark plug if the carbon has already formed corrosion.


How To Change A Spark Plug On A Lawn Mower

Sludge between the gaps.

Because the central electrode and the ground electrode are both made of nickel alloy, they can also corrode over time which can alter the creation of sparks that is needed for combustion.

You can use fine grade sandpaper to brush the corrosion out and try to restart the engine after cleaning. If the engine won’t start, replace the spark plug with a new one.



How To Change A Spark Plug On A Lawn Mower
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Improper gaps between electrodes.

There should always be the ideal gap between the point of the central electrode and the ground electrode.

If the gap gets wider or thinner, no electricity can be produced.

Use a feeler gauge to measure the gap in between the two electrodes and follow your User’s Manual about the ideal gap.

If the ground electrode has badly bent, better replace your spark plug .

How To Change A Spark Plug On A Lawn Mower

Old and faulty spark plug.

Most of the time, the problems occur inside the spark plug itself as it becomes old and defective.

It’s obvious that you need to change your spark plug with a brand new one if it is  faulty due to prolonged use.

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Symptoms lawn mower Spark Plug Problems

Hard starting:

Spark plug not able to produce enough sparks.

Probable cause:

Gas flooding, excess oil that seeps right into the spark plug chamber.


Unflood the carburetor by resting it for about 15 minutes and removing the air filter, drain out excess oil, unplug the spark plug and clean or replace it.

Engine poor performance:

Engine starts, runs and then dies.
Probable cause:

Flooding, bad air filter, the spark plug is misfiring caused by the improper gap between electrodes.


 Unflood the carburetor, clean or replace air filter, use a gauge feeler to correct the gap on the spark plug or replace it with a new one.

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How to change a spark plug on a lawn mower is basically one of the easiest things you can do when maintaining or fixing a lawn mower.

However, you have to be observant when taking out the plug and you need to see what’s going on even inside the spark plug’s chamber.

To avoid delay in your mowing work, always have a reliable spark plug in your garage and of course, be ready with your spark plug wrench.

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