Oilers/Plant Tenders (HHC) Civil Service Practice Exam

What tool is MOST accurate for setting the proper gap on a spark plug?

1. Digital caliper

2. Round wire feeler gage

3. Standard ruler

4. Thickness gauge

The correct answer is: Round wire feeler gage

The round wire feeler gauge is the most accurate tool for setting the proper gap on a spark plug due to its design and intended use. Feel gauges, particularly those made with round wire, can conform to the shape of the spark plug's electrode gap, allowing for precise measurement of the gap size. This accuracy is crucial as it directly affects the performance of the engine; an incorrect gap can lead to misfiring or inefficient combustion. In contrast, a digital caliper, while capable of measuring small dimensions accurately, is less versatile for this specific application due to its bulk and the need for precise alignment to get an accurate reading in the confined space of a spark plug. A standard ruler may not provide the level of precision required, as it typically lacks the subtleties and small incremental measurements needed for spark plug gapping. Similarly, a thickness gauge is used for different applications and may not offer the same level of accuracy or ease of use when it comes to setting spark plug gaps. This makes the round wire feeler gauge the optimal choice for achieving precise and reliable spark plug gap settings.