FAA Powerplant Written Practice Test

When is a spark plug considered fouled?

1. When it shows physical damage

2. When it fails to produce a spark

3. When its spark grounds without jumping electrodes

4. When there is excessive wear on the electrodes

The correct answer is: When its spark grounds without jumping electrodes

A spark plug is considered fouled when it fails to produce a proper spark due to deposits or buildup that prevent the electrical discharge between the electrodes. This typically happens when the spark plug grounds without effectively jumping the electrodes, which means that the spark doesn't jump across the gap as intended. Various contaminants, such as carbon deposits, oil, or fuel residues, can collect on the spark plug and hinder its ability to create a spark, causing it to misfire or not operate at all. Understanding the condition of the spark plug is critical, as fouling often leads to performance issues in the engine, including rough running or starting difficulties. Recognizing the symptoms of fouled spark plugs is essential for maintenance and troubleshooting in aviation systems, especially for internal combustion engines where reliable ignition is crucial for performance.