When an air started, four-stroke cycle diesel engine is being cranked over, the starting air is admitted to each cylinder during the beginning of its __________.

The starting air is admitted to each cylinder during the beginning of its power stroke in a four-stroke cycle diesel engine. This moment is crucial because, in this context, the engine is utilizing the stored compressed air to initiate combustion. When the starting air is injected at the beginning of the power stroke, it helps compress the air-fuel mixture that is necessary for the engine to generate the power needed to keep running after the initial cranking.

In a four-stroke engine, the cycle consists of intake, compression, power, and exhaust strokes. During the intake stroke, the cylinder fills with air, and during the compression stroke, that air is compressed. The power stroke is where the actual work is done as the combustion occurs, leading to the movement of the piston. Since the purpose of the starting air is to facilitate the ignition process and initiate the power phase, it is critical to understand that the air is introduced just as the piston is beginning the power stroke.

In summary, the accurate knowledge of the timing and purpose of the starting air’s introduction is essential for effectively operating and troubleshooting a diesel engine.