An internal combustion engine which is a four-stroke engine that is also known as four cycle engine has four step to complete one revolution. That means while turning a crankshaft, the piston completes four separate strokes. When the piston fully travels along the cylinder a stroke happens, it can be in either direction. Those four separate strokes can be described as below:
Intake Stoke: Intake is the 1st step what is also known as induction. In the stroke of the piston begins at top dead center and thats ends at the bottom dead center. The intake valve must be in the open position in this stroke while the piston pulls an air fuel mixture into the cylinder. And air fuel mixture is pulled by producing vacuum pressure into the cylinder through it’s downward motion. That’s how the intake stroke works.
Compression Stoke: Compression stroke begins at bottom dead center, you can also tell that it starts just at the end of the intake stroke and Compression stroke ends at top dead center. The piston compresses the air fuel mixture in this stroke in preparation for ignition during the power stroke which 3rd and next stroke. During this stage the intake & exhaust both valves are closed.
Power Stoke: Power Stoke is also known as Combustion stoke. In this stoke the second revolution of the four stroke cycle starts. The crankshaft completes a full 360 degree revolution at this point. While the piston is at top dead center the compressed air fuel mixture is ignited by heat generated by high compression in diesel engines at the end of the power stroke. Which forcefully returning the piston to bottom dead center. Power stroke produces mechanical work to turn the crankshaft from the engine.
Exhaust Stoke: Exhaust Stoke is also known as outlet stoke. The piston once again returns from bottom dead center to top dead center during the exhaust stroke. And the exhaust valve is open then. This action ejects the spent air fuel mixture through the exhaust valve.
That was the four strokes to complete one revolution of the diesel engine.