What does the fuel/air control unit in a fuel injection system do?

The fuel/air control unit in a fuel injection system is responsible for controlling the fuel flow based on the engine's demands. This unit continuously adjusts the amount of fuel that is injected into the combustion chamber in response to various parameters such as engine speed, load, and temperature. By doing so, it ensures an optimal air-fuel mixture for efficient combustion, which leads to better performance and fuel efficiency.

With precise control over fuel flow, the fuel/air control unit helps to achieve the correct mixture for various operating conditions, enhancing engine responsiveness and reducing emissions. This dynamic management is crucial for maximizing the engine's efficiency and overall performance.

In comparison, the other options present functions that either do not align with the primary role of the fuel/air control unit or describe processes that occur earlier in the system. Measuring fuel pressure and mixing fuel and air before combustion are important tasks in the fuel delivery process, but they do not accurately define the core function of the fuel/air control unit. Storing excess fuel is also not a function of this unit, as its purpose is focused on actively regulating the amount of fuel supplied to the engine rather than holding excess fuel.