What is the primary purpose of an accelerator pump?

The primary purpose of an accelerator pump is to prevent a weak cut when the throttle lever is advanced rapidly. When the throttle is opened suddenly, there is typically a delay in fuel delivery from the main jets of the carburetor due to the change in airflow. This delay can lead to a momentary lean mixture, causing hesitation or stalling in the engine—commonly referred to as a "weak cut."

The accelerator pump addresses this issue by providing an additional squirt of fuel into the intake manifold at the moment the throttle is opened. This extra fuel compensates for the lean condition and ensures that the engine receives a richer mixture during rapid acceleration, thus maintaining performance and responsiveness. This function is critical for smooth engine operation, especially during quick throttle movements, allowing the engine to have a seamless power delivery.

In contrast, while the other options discuss various functions related to fuel delivery and combustion stability, they do not define the primary function of an accelerator pump. Thus, the emphasis on preventing a weak mixture during sudden acceleration is the key role that the accelerator pump plays in engine performance.