An improved primary pump for a carburetor is provided. The primary pump has a reduced cost and reduced space construction. The primary pump includes: a flexible cap having a cavity; an inlet open to the cavity of the flexible cap; an inlet side path fluidly coupled to the inlet; an inlet side check valve disposed in the inlet side path; an outlet open to the cavity of the flexible cap; an outlet side path fluidly coupled to the outlet; and an outlet side check valve disposed on the outlet side path, wherein at least one among the inlet side check valve and the outlet side check valve comprises a flap formed in a pump diaphragm of a fuel pump of the carburetor.