By Mathew League The heart of any hydraulic system is the hydraulic pump. The pump is responsible for moving the fluid through your hydraulic system, and building the pressure required to perform the work required. There are several types of hydraulic pumps, but the simplest and least expensive is the gear pump. A gear pump operates by having two gears that mesh together, one of which is connected to the inlet shaft. The fluid is drawn into the inlet and pulled around the outside of the two gears between the gear teeth and the body of the pump. Once the fluid has reached the outlet side of the pump, the fluid is forced out the outlet port from the force created by the teeth of the gears meshing back together.