FAA Powerplant Inspections Practice Test

A common cause of a cold or dead cylinder in a reciprocating engine is defective spark plugs. Spark plugs are essential for igniting the fuel-air mixture in the combustion chamber. If a spark plug is malfunctioning, it can result in incomplete combustion or no combustion at all in that specific cylinder, leading to it running cold or not firing.

When a spark plug fails due to fouling, carbon build-up, or damage, it disrupts the ignition process. This condition can lead to a significant loss of power, rough engine operation, and increased emissions, which are all indicators that one or more cylinders are not firing correctly. In diagnosing a cold cylinder issue, checking the spark plugs is often one of the first steps technicians take.

Other factors, such as low oil pressure, clogged fuel filters, or worn piston rings, can affect engine performance but are less likely to be the immediate cause of a cylinder failing to fire. Low oil pressure typically impacts lubrication and engine wear rather than the ignition process. A clogged fuel filter affects fuel delivery but would generally cause broader performance issues rather than isolating a problem to a single cylinder. Worn piston rings could lead to compression issues but would usually manifest differently than simply having a cold cylinder.

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