How to gap spark plugs with a feeler gauge

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Step 1 – Check gap meets spec

Use your feeler gauge to check the spark plug gap meets the specification for your vehicle.

You may need to adjust the spark plug gap from its out-of-the-box state.

Step 2 – Bend ground electrode

To alter the gap, bend the ground electrode slightly away from or toward the centre electrode.

Step 3 – Use other tools if necessary

Spark plug gapping tools are available, however, sometimes a small mallet, wrench, or pliers can be used to adjust the gap slightly.

Step 4 – Place gauge between electrodes

Re-check the gap by placing the feeler gauge between the two electrodes.

The gap must meet the vehicles specification so the spark plug can fire efficiently.