Question 188Motor Plants - Assistant Engineer

The correct answer is C) power stroke. 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 power stroke. This is because the power stroke is the phase of the engine cycle where the piston is moving downward, and the combustion of the air-fuel mixture provides the force to turn the crankshaft and start the engine. The other options are incorrect because the starting air would not be admitted during the intake, compression, or exhaust strokes, as those are not the optimal points in the engine cycle for starting the engine.