Bosch-Common Rail System – Transfer Pump
1 Intake side
2 Drive gear
3 Delivery side
The transfer pump is designed as a gear pump and delivers the required fuel to the high-pressure pump. Essential components are two counter-rotating, meshed gear wheels that transport the fuel in the tooth gaps from the intake side to the pressure side. The contact line of the gears forms a seal between the intake side and the pressure side and prevents the fuel from flowing back. The delivery quantity is approximately proportional to engine speed. For this reason, fuel-quantity control is required. For fuel-quantity control purposes, there is an overflow reducing valve incorporated in the high-pressure pump.