FAA Powerplant Written Practice Test

Which of the following problems could be detected by a cold cylinder check?

1. A defective spark plug lead

2. A fuel leak in the system

3. An overheating engine

4. A worn cylinder wall

The correct answer is: A defective spark plug lead

A cold cylinder check is a diagnostic procedure primarily used to identify issues related to the engine's ignition system and cylinder performance. During this check, the temperature of each cylinder is measured after the engine has been run and then allowed to cool down. When considering the issues that can be detected, a defective spark plug lead would lead to one or more cylinders not firing correctly, resulting in a temperature difference between the affected cylinder and those that are functioning properly. This temperature discrepancy is easily detectable during a cold cylinder check, as the cylinder with the defective lead will remain cooler than the others, indicating a lack of combustion. In contrast, the other options are less directly observable through a cold cylinder check. A fuel leak might not affect the cylinder temperatures immediately and would typically require visual inspections or other leak detection methods. An overheating engine would more likely show elevated temperatures across the board during operation, making a cold cylinder check less effective in diagnosing this condition. Worn cylinder walls, while they can lead to a loss of compression and subsequent performance issues, would not be directly indicated through temperature differences observed in a cold cylinder check. Therefore, identifying a defective spark plug lead is particularly suited for detection during a cold cylinder check, as it highlights a specific problem related to ignition that