How to Test Your Spark Plugs

Shop Spark Plugs

Spark plugs play a crucial role in your vehicle's engine, ensuring the combustion process runs smoothly. Over time, these plugs can wear out or malfunction. But how can you determine if your spark plug is still in working order? Let's dive into the simple process of testing your spark plugs.

---
 

Understanding the Spark Plug Components

A spark plug might seem like a small component, but it's essential for your engine's performance. Here's a breakdown of its parts:

• End Connector: This is where the spark plug wire clamps onto.
• Porcelain Insulator: Surrounding the central metal pin.
• Nut: Extends out to the end that screws into your engine.
• Side Electrode: A piece of metal that arches over the top.
• Central Electrode: A tiny pin in the middle, connected to the end connector. The dark area surrounding this pin is also made of porcelain.

When testing a spark plug, you're essentially checking the resistance (in ohms) passing through from the tip to the end of the metal electrode.
 

Testing Your Spark Plug with a Multimeter

To begin, grab your multimeter and set it to the 20K ohms setting. Next, position the two probes of your multimeter ensuring that one touches the terminal end of the spark plug, and the other touches the top of the central electrode.
 

When reading the results, the multimeter should show no reading if you're touching any of the metal portions (i.e. the nut) of the spark plug. However, when both probes are correctly positioned with one on each end of the spark plug (the central electrode and terminal), a reading between 5 and 15 on the multimeter will indicate a functional spark plug.

A multimeter reading between 5 and 15 when touching the terminal end and the top of the central electrode indicates that your spark plug is in good shape. If there's no reading, the metal running insulated between these two points might be broken. Additionally, a reading occuring when one probe is touching the terminal and the other is touching any other metal portion of the spark plug (i.e the nut) is an indicator of a malfunctioning spark plug.

---
 

In conclusion, testing your spark plugs is a straightforward process that can save you from potential engine troubles down the road. By using a multimeter and understanding the basic components of a spark plug, you can ensure your vehicle's engine runs efficiently. If in doubt, always consult with a professional mechanic.

If you have questions about any of the information above or are just more of a visual learner, head over to our YouTube channel and watch our video (also attached below)! Leave a comment or question and receive a personal reply from Brent, our resident John Deere expert. Be sure to subscribe and thanks for reading!