How to Tell If Lawn Mower Spark Plug is Bad

If your lawn mower isn’t starting, one possible reason is a bad spark plug. Here’s how you can tell if your spark plug is bad and what you can do about it. A spark plug is an essential part of a lawn mower engine, providing the spark that ignites the fuel.

If the spark plug is fouled or damaged, it won’t be able to provide a good spark and the engine won’t start. There are a few signs that can indicate a bad spark plug: -The engine won’t start or is very difficult to start

-The engine runs rough or misfires If you suspect your spark plug may be bad, the first thing to do is check the gap. The gap should be between .030 and .040 inches.

If it’s too wide or too narrow, the plugs need to be replaced.

  • Check the lawn mower’s spark plug to see if it is damaged or covered in debris
  • If the spark plug looks damaged, clean it off with a wire brush and reinstall it
  • If the spark plug still does not work, replace it with a new one
  • To test if the new spark plug is working, pull the cord to start the lawn mower and look for a spark at the end of the plug

How to Check If Lawn Mower Spark Plug is Firing

It’s easy to take your lawn mower for granted. You just fill it with gas, pull the cord, and away you go. But when it stops working, it can be a real pain.

One of the most common reasons a lawn mower won’t start is because the spark plug isn’t firing. Here’s how to check if your lawn mower spark plug is firing: 1. Remove the spark plug from the lawn mower engine.

2. Inspect the spark plug for damage or corrosion. If there is any damage, replace the spark plug with a new one. 3. Reattach the spark plug to the engine and hand-tighten it until snug.

Do not over-tighten! 4. Pull on the starter cord while holding the end of the spark plug close to ground (a metal surface will do). You should see a strong blue sparks coming from the gap between electrodes at the end of the plug if it is firing correctly.


Will a Lawn Mower Start If the Spark Plug is Bad?

No, a lawn mower will not start if the spark plug is bad. The spark plug ignites the fuel in the engine, so without it, the engine cannot run. You can test your spark plug to see if it is working properly by removing it and testing it with a multimeter.

How Long Do Spark Plugs Last in a Lawn Mower?

Spark plugs are a vital part of any lawn mower, and they need to be replaced regularly to keep the mower running smoothly. How often you need to replace them depends on how often you use the mower and what kind of spark plugs you have. Generally speaking, spark plugs should be replaced every 25 hours of use or so.

If you’re using your lawn mower for heavy-duty work, like commercial landscaping, you may need to replace the spark plugs more often. It’s a good idea to check the condition of your spark plugs every few months and replace them if necessary.

What Does a Bad Spark Plug Do to a Mower?

A bad spark plug can cause a number of problems for your lawn mower. The most common problem is that it will prevent the engine from starting. If the spark plug is old or worn out, it may not create enough of a spark to ignite the fuel in the engine.

This can make it difficult or even impossible to start your mower. Another problem that a bad spark plug can cause is that it can make the engine run rough. This is because the spark plugs are responsible for igniting the fuel in the cylinders.

If they aren’t working properly, the fuel won’t be burned as efficiently and this can lead to a loss of power and performance. The engine may also stall more often if the spark plugs are faulty. In some cases, a bad spark plug can also cause damage to other parts of the mower’s engine.

For example, if there isn’t enough of a spark to ignite all of the fuel in the cylinder, this can cause “knocking” which puts stress on other components like pistons and connecting rods. Over time, this extra wear and tear can lead to serious engine damage. So, as you can see, having bad spark plugs in your lawn mower can have some pretty serious consequences!

If you’re having trouble starting your mower or if it’s running rough, it’s definitely worth checking your plugs to see if they might be at fault.

How Can You Tell If Your Spark Plugs Bad?

If your spark plugs are bad, it’s likely that your car will experience some engine performance issues. The most common symptom of bad spark plugs is a loss of power while driving, as well as decreased fuel economy. Your car may also run rougher than usual and may misfire from time to time.

If you suspect that your spark plugs may be bad, the best way to confirm this is to have them checked by a mechanic.

Mower Spark plug….Don't Get Fooled!! (Like I almost did)


If your lawn mower isn’t starting, one possible reason is a bad spark plug. There are a few ways you can tell if your spark plug is bad. One way is to look at the end of the plug.

If it’s black or covered in soot, that’s an indication that the plug is fouled and needs to be replaced. Another way to tell if the spark plug is bad is by looking at the gap between the electrode and the metal tip. The gap should be about 1/16 of an inch.

If it’s wider than that, the spark plug needs to be replaced. Finally, you can try cleaning the spark plug with a wire brush and then re-gap it. If it still doesn’t work, chances are you need a new one.