How to remove a stuck spark plug from a lawnmower engine

Tuesday, January 24, 2023

I was at my mom's over Christmas and her lawns needed mowing. 

So I pulled out the 'ancient beast' to mow the lawns, and dang it, the mower simply would not start into life, try as I might.

On investigation of the spark plug, I noted it was heavily rusted so I deduced that was the problem. I grabbed a spanner and got to work - the plug would not budge, it was bloody stuck. I know I was using the wrong tool, but needs mus so I eventually managed to free the plug with some old pliers. 

Nether-the-less, I persisted and removed the plug but the moment got me thinking, what if it was really stuck, how would I remove it? 

I did some digging, talked to the neighbour and came up with a guide to finding ways to remove a stubborn and stuck spark plug in a lawn mower - I reckon the same tips would probably apply to a chainsaw or petrol/gas powered weed whacker too!

remove stuck spark plug
You will need a spark plug wrench to remove the stuck plug. These can come in various shapes and forms - they can often be found in socket sets. 

It's always best to do lawn mower maintenance on a flat, level surface.

A simple one for a Briggs and Stratton mower looks like this for example:

spark plug wrench

Use penetrating oil: 

Spray penetrating oil, such as WD-40 or CRC lubricant, onto the spark plug and the surrounding area. Allow the oil to sit for a few minutes to loosen any rust or corrosion. Then, use a spark plug wrench to loosen the spark plug. Be gentle, don't force the tool too hard or you could cause damage to the plug compounding your issue.

Tap the spark plug: 

You can use a rubber mallet or a small piece of wood to tap the top of the spark plug gently. This may help to help to loosen any rust or corrosion that may be holding the spark plug in place. Like the above, don't hit it too hard. 

Those are the two simple methods, the next requires the use of a unique tool, a broken spark plug remover.

A broken spark plug remover is a specialized tool that can be used to remove a stuck spark plug. 

You can insert the tool into the spark plug, then turn it to grip the spark plug and remove it.

Use heat to expand the metal:

We think this next tip may be a bit of a loose strategy but it kinda makes sense. 

Apply heat to the spark plug by using a propane torch or heat gun. Be careful not to overheat the spark plug, as this can cause damage to the engine. The heat will expand the metal, making it easier to remove. After heating the spark plug, wait for a moment to cool down, then use a spark plug wrench to remove it.

If none of these methods works, it may be best to seek the help of a professional mechanic or a lawnmower repair shop as they will have specialized tools and expertise to remove a stuck spark plug without causing damage to the engine.
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