FAA Powerplant Written Practice Test

What tool should be used to obtain the correct gap setting on a spark plug?

1. A torque wrench

2. A wire thickness gauge

3. A feeler gauge

4. A digital caliper

The correct answer is: A wire thickness gauge

The correct tool for obtaining the gap setting on a spark plug is a wire thickness gauge. This tool is specifically designed to measure the thickness of the wire, which allows the technician to determine the correct spacing between the center electrode and the ground electrode of the spark plug. Maintaining the proper gap is crucial for optimal engine performance, as it ensures efficient ignition of the air-fuel mixture. The wire thickness gauge typically comes with various sizes that correspond to different gap measurements, making it easy to find the correct setting as specified by the engine manufacturer. While there are other tools available, such as torque wrenches, feeler gauges, and digital calipers, they serve different purposes. A torque wrench is used to apply a specific amount of torque to fasteners, ensuring they are tightened to the manufacturer's specifications but does not measure spark plug gaps. A feeler gauge, similar in function to a wire thickness gauge, can also be used to measure gaps; however, it is less common for this specific task in the context of spark plugs. A digital caliper is primarily used for measuring dimensions but is not specifically tailored to the task of gap measurement in spark plugs. Thus, the wire thickness gauge stands out as the most appropriate choice for this application.