A check valve comprises a housing, a fluid passage, a seat, a valve member and a stop. The fluid passage extends through the housing. The seat is disposed in the fluid passage. The valve member is positioned in the passage to engage the seat. The stop extends through the housing to engage the valve member. The stop is accessible from outside the housing to adjust a distance the valve member can travel from the seat. In one embodiment, the stop includes a variable stop feature, such as an offset pin or a cam. In another embodiment, the stop includes a pump control valve. In yet another embodiment, the housing includes markings to indicate a position of the stop. The valve member comprises a ball or a poppet in different embodiments.