Abstract: A diaphragm type carburetor which has a purge system to remove air and fuel vapor from the carburetor and to fill it with liquid fuel prior to starting an engine fed by the carburetor. The purge system has a primer valve actuated by moving a choke valve of the carburetor to its closed position to inject a small volume of liquid fuel into a throttle bore to provide a richer fuel and air mixture to the engine to facilitate starting it. Desirably, the small volume of liquid fuel is injected into the throttle bore in response to closing of the choke valve without requiring any additional steps such as depressing a button on the carburetor, to do so. Preferably, the choke valve is carried on a shaft which has at least one detent formed therein to provide a camming surface which actuates the primer valve as the choke valve is rotated from its open position to its closed position. Preferably, the choke valve shaft has a pair of detents.