Lawn Mower Spark Plug

Like all equipments and devices, lawn mowers to undergo a lot of wear and tear and hence require regular maintenance.


If you carry out regular maintenance of the filters, oil, fuel and other standard tuning up procedures you can have your mower running smoothly for a very long time.

However, there are times when despite regular tuning, the mower falters. One of the first places to would be the lawn mower spark plug.

The spark plug is the component that can spark and start the engine in the mower. With the ignition the mower will not function.

The role of the spark plug is so fundamental that it is no surprise it is one of the first things that people check if their mower does not start – besides the fuel, of course.

While it is important, it is also one of the most dangerous parts if the mower too. Since it produces spark, if it is not stowed away safely during the maintenance, the sparks could light up the fuel and lead to dangerous circumstances.

There are some simple tips on maintaining the lawn mower spark plug.

Cleaning the lawn mower spark plug maintenance

The most common care that you need to take with your spark plug is to clean the same. If you have too much soot on the spark plug there is a good chance that your mower will stall regularly and will not start properly too.

  • The first step in cleaning the spark plug is to remove it from the mower.
  • Locate the spark plug wire on your mower. This should not be that difficult to locate, you can also use the manual as aid in this case.
  • Once you have the spark plug wire, trace it till you reach the spark plug.
  • Now you need to first wriggle it out of the position.
  • Once you have disconnected the spark plug wire, you can now proceed with removing the spark plug itself.
  • Once removed, you can check for dirt and soot and clean it with a wire brush.

How to change a spark plug on a lawn mower

lawn mower spark plug lawn mower spark plug

For a uniform and easy starting, spark plugs are recommended to be changed every season or on the interval of every 100 hours.

Below are the steps on replacing the spark plug of your lawn mower.


  • In removing the existing spark plug, disconnect the lead of the spark plug. Clean around the area of the spark plug to eliminate catching the debris on the combustion chamber when removing the spark plug.

  • With the aid of the spark plug socket, remove the spark plug.

  • Clean with a brush those light deposits that have been accumulated on the spark plug and spray on it a plug cleaner. Use a tough knife to remove those hard deposits. Never use abrasives or shot blaster when cleaning the spark plugs.

  • Carefully examine the spark plug for any deposits like cracked porcelains and electrodes that have been burned.

  • In putting the new spark plug, measure the gap of the two electrodes with the tip of the spark plug using a spark plug gauge. Most of the small engines demand a 0.030 inch gap. Check the specifications of your lawn mower model.

  • If there are necessary adjustments to be made with the gap, use the spark plug gauge to adjust it. If the gap is right, the gauge will slightly drag while pulling through the gap.

  • Install the plug again, make sure not to over tighten it with the maximum strength of only 15 ft. lbs. Afterwards, attaché the lead of the spark plug.

Safety Tips while working with spark plug

Deal with spark

Lawn mower spark plug is designed to ignite the engine by creating a spark.

However, due to its nature, there are times when it could spark unnecessarily.

The chance of this happening is typically while carrying out other maintenance work on the mower like replacing the blades.

Disconnect the spark plug

Hence, you will find in almost all the lawn mower maintenance instructions that before you do any repair work on your mower, you must disconnect the spark plug and store it away safely.

In conclusion, knowing to replace the spark plug is a very good skill to know.

As you can see, it is not just while replacing the plug itself that you need to remove it; you need to take it out for almost every other maintenance work too.

If you learn this trick with your mower soon, you can save a lot of time and money by not having to go to the service center for simple maintenance work.

Service Your Spark Plug

Spark plugs should be changed every 100 hours or every season, whichever comes first.

Remember that replacing your spark plug regularly will ensure a consistent, easy spark and it will also improve fuel economy.

If your spark plug is worn or dirty more voltage will be required to produce a satisfactory spark.

You can easily and successfully service your spark plug if you follow these simple instructions.

It will just take 15 minutes of your time. All you need is a spark tester, a spark plug socket, a socket wrench, a wire brush, a plug cleaner and a spark plug gauge.

This is what you need to do:

  • Disconnect the spark plug lead and clean the area around it.
  • Use a spark plug socket to remove the spark plug.
  • Use a wire brush and a spray-on plug cleaner to clean light deposits from the plug. If there are some tough deposits you may try scraping them off by means of a sturdy knife. Remember NEVER to use abrasives to clean your spark plug, since they may severely damage it.
  • Should you find burnt electrodes or cracked porcelain, you spark plug will need to be replaced.
  • Measure the gap between the straight and curved electrodes at the tip of your spark plug by means of a spark plug gauge.
  • Once you have done all this, reinstall your spark plug and re connect the spark plug lead.

How to test ignition with a Spark Tester

Spark testers are highly effective in that they can help you identify ignition problems in a cheap and easy way.

If you happen to notice something is wrong with your spark plug, remove it and inspect it following these steps:

  • Connect the spark plug lead to the long terminal of the spark tester.
  • Use the tester’s alligator clip to ground the tester to the engine.
  • Crack the engine by means of the rewind or electric starter.
  • Check out for a spark in the tester’s window: the presence of a spark indicates that the ignition is functioning, whereas if you cannot see a spark it means there is certainly a problem in the ignition system.

How to check for Spark Miss with a Spark Tester

If you notice that your engine stumbles or emits black smoke, it may mean that it the spark plug is failing to spark.

This problem is known as a spark miss, and this here’s how you can check for it:

  • Screw the spark plug into the cylinder head.
  • Attach the spark plug lead to the long terminal of the tester.
  • Attach the alligator clip to the spark plug.
  • Start the engine. If there is a spark miss, the sparks in the tester will fire erratically.

Related Articles:

Lawn mower tune up instructions for all kind of engine.





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