A pump includes a pump housing and an end cap, which is attached to the pump housing at the top and has an oil suction port at one end and an oil relief port at one lateral side. A connecting cap is connectable to the end cap opposite to the pump housing in one of a number of positions in different directions and which has two ports cut through the two opposite ends thereof for letting in and out a fluid to/from a hydraulic motor. Two plugs are selectively fastened to one of the two ends of each of the two ports of the connecting cap to control the flow direction of the fluid passing to/from the hydraulic motor through the connecting cap.