Abstract: A pulse generator used for a one-step starting carburetor includes a pulse chamber, a lower cover, a support and a solenoid valve. Two types of pulse are produced in the pulse chamber: the normal pulse and the crowding pulse. The normal pulse provides the normal pulse force for the carburetor. When the engine starts in cold, the crowding pulse goes into the carburetor to concentrate the gas mixture in a mixing chamber of the carburetor. The pulse generator described herein solves the problem that the pulse force is insufficient in the four-stroke engine. The original suction pulse is modified to two directions of a suction pulse and a blowing pulse. The fuel pumping capacity of the oil pumping unit which is connected with the carburetor is greatly increased to improve working stability of the engine.