FAA Powerplant Written Practice Test

How can the correct gap setting on a spark plug be achieved before installation?

1. By visual inspection

2. Using a wire thickness gauge

3. With a digital caliper

4. Simply by feel

The correct answer is: Using a wire thickness gauge

Achieving the correct gap setting on a spark plug is essential for optimal engine performance. Using a wire thickness gauge is the most accurate method for measuring the gap between the center and ground electrodes of the spark plug. This tool allows a technician to check specific gap sizes precisely, ensuring it meets the manufacturer's specifications. When employing a wire thickness gauge, the gauge is inserted into the gap to measure its size. If the gap is incorrect, adjustments can be made by carefully bending the ground electrode until the desired gap is achieved. This method ensures the spark plug operates efficiently and produces a proper spark, which is critical for ignition and combustion in the engine. Other methods, such as visual inspection, may lead to subjective judgment and inaccuracies, as they rely on what the technician can see without precise measurement. A digital caliper is a specialized tool for measuring distances but may not be as effective or practical in measuring spark plug gaps compared to a wire thickness gauge. Using simply feel can lead to inconsistent results and is not a reliable technique for achieving the correct gap. Therefore, the wire thickness gauge stands out as the best choice for this task.