Technician A claims that a cracked spark plug increases firing voltage, while Technician B claims a fouled spark plug does as well. Who is correct?

A cracked spark plug does not inherently increase firing voltage. In fact, a crack can create a path for the electrical current to escape, which can lead to a misfire or insufficient spark energy needed for combustion. The firing voltage may drop, resulting in poorer engine performance.

Similarly, a fouled spark plug, which can be covered with carbon deposits, oil, or other contaminants, does not increase firing voltage either. It typically leads to a higher resistance in the ignition circuit, requiring more voltage to jump the gap or potentially causing a misfire. In essence, both conditions would lead to challenges in achieving the necessary spark for efficient combustion, rather than contributing to an increase in firing voltage.

Thus, neither technician's statement is accurate in the context of how a cracked or fouled spark plug affects firing voltage.