In an air starting system, how is the engine started?

The engine in an air starting system is initiated using compressed air applied to the pistons. This method leverages pressurized air to create sufficient force to drive the engine's pistons downward, which in turn sets the engine in motion and allows it to start running. This type of starting system is particularly beneficial for large engines, such as those found in marine applications, where an electric starter may not have the power needed to crank the engine effectively.

Using compressed air is advantageous because it can be stored in tanks and can provide a strong, initial push to overcome the inertia of the engine without requiring electrical components or manual labor. This system is efficient and effective in environments where reliability and power are crucial, such as on ships or in industrial settings.

In contrast, options involving fuel injection or manual cranking do not relate to the air starting mechanism. Fuel injection is essential for the operation of internal combustion engines but is not involved in the initial start process itself, while manually cranking the engine does not apply to modern large engines using an air starting system. Lastly, while electric starters are common in many applications, in the context of this specific question, they are not utilized in an air starting system.