Question 187Motor Plants - Assistant Engineer

The correct answer is B) the spring force and cylinder pressure. In a direct cylinder admission air starting system, once the engine begins to fire, the air starting check valve is closed by the spring force and the increasing cylinder pressure. As the engine starts, the cylinder pressure rises, which, combined with the spring force, pushes the check valve closed to prevent the air pressure from flowing back into the starting air system. This ensures that the engine can continue running on its own power without the need for the starting air supply. The other options are incorrect because: A) the starting air pressure alone does not close the valve, B) the spring force and cylinder pressure are the correct mechanism, C) a valve actuating cam is not involved in this process, and D) a pneumatic bellows assembly is not part of the direct cylinder admission air starting system.