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How to Gap Spark Plugs

how to gap spark plugs
If you’ve ever wanted to know what spark plug gap is and how to gap spark plugs, Blain’s Farm & Fleet has the answers you need.

Many DIY auto repair mechanics aren’t aware that there is any such thing as gapping a spark plug. Some know about it, but don’t know how to gap spark plugs. Some think it doesn’t matter. At any rate, most people just assume that you buy the plug, put it in, and you’re good. In some cases, this will work. The engine will fire and run just fine. However, your engine is designed to work most efficiently when the spark plugs are gapped to the width specified in your owner’s manual.

How to Gap Spark Plugs

Step 1. Check your owner’s manual to find out what gap you need.

Step 2. Measure the gap of your new spark plugs.

On the threaded end of the spark plug, you’ll see a point with a curved metal strip over it. The gap is the space between the point and the strip. The strip is called the ground electrode and the tip is called the center electrode. To measure the gap, you’ll need a spark plug gapping tool or a feeler gauge and some pliers. You can use the gapping tool to both measure and adjust the gap on a plug. The feeler gauge can measure more accurately, but you’ll have to use the pliers to adjust the gap. Check out our blog to learn more about spark plug gapping tools vs. feeler gauges. If your measurement matches what your owner’s manual recommends, you’re done. If it doesn’t, move on to step 2.

Step 3. Use the spark plug gapping tool or the pliers to bend the curved ground electrode.

If your measurement was smaller than the number in your owner’s manual, bend the ground electrode away from the plug to make the gap larger. If your measurement was bigger, push the ground electrode closer to the center electrode. Measure after every bend and stop when your measurement matches the number in your owner’s manual.


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