How to Gap Spark Plugs

Whether you're replacing the spark plugs in your car engine or lawnmower, you'll need to set the gap before reseating the spark plug. The gap is the distance electricity arcs between the ground electrode and center electrode. The gap must be set correctly to ensure maximum performance. Here's how to set the gap of a spark plug.

Difficulty: Easy

Instructions

1. Remove the spark plug wires. Use a socket wrench to remove the spark plugs from their chambers.

2. Clean the spark plug if you are not replacing it with a new one. Remove all dirt and debris from the spark plug.

3. Check the owner's manual for your car (or any appliance with spark plugs) to find out the recommended gap setting.

4. Use a gap tool to check the gap of the spark plug. Slip the tool between the ground electrode and center electrode. The gap tool should fit snugly at the recommended gap width indicated on the tool.

5. Push the tool between the electrodes a few times to ensure proper gap. If the gap is too wide, push the ground electrode firmly against a flat surface to narrow the gap and then check again with the gap tool.

6. Repeat Step 5 as necessary until you reach the correct gap. Reseat the spark plug and reattach the spark plug wires.

Tips & Warnings

• A narrow gap is recommended over a wider gap. The gap tool should fit tightly between the electrodes.
• Setting the spark plug gap too wide can cause engine misfirings or hard starting when the engine is cold.