AG Mechanics CDE Practice Exam

The air-fuel mixture is forced into the intake manifold by ____________.

1. Atmospheric pressure

2. Exhaust pressure

3. Fuel pump pressure

4. Vacuum pressure

The correct answer is: Atmospheric pressure

The correct answer is atmospheric pressure because in a typical combustion engine, the intake manifold is where the air-fuel mixture is created before being sent into the combustion chamber for ignition. Atmospheric pressure plays a crucial role in this process by pushing air into the intake manifold when the intake valve opens. This creates the necessary pressure differential for the fuel to mix with the air and be drawn into the combustion chamber during the intake stroke. Exhaust pressure (Option B), fuel pump pressure (Option C), and vacuum pressure (Option D) do not perform the specific function of forcing the air-fuel mixture into the intake manifold in the same way atmospheric pressure does. Therefore, they are not the correct answers in this context.