The accelerating pump controls the amount of additional fuel that is discharged in the air stream on sudden throttle openings.

The accelerating system consists of a pump assembly, accelerating jet, an intake check valve, an air check valve, the three parts of which make up the refill check valve and the mechanical linkage which connects to the throttle linkage.

The pump assembly controls the amount of fuel that is delivered to the accelerating jet. This may be varied by adjusting the pump stroke. Three grooves at the upper end of the pump rod provide a means of varying the pump stroke. When the cotter pin is placed in the bottom groove, the full stroke of the pump is available to discharge the largest volume of fuel.