Working principle of fuel metering unit

What is a fuel metering unit? Take BOSCH as an example, fuel metering unit is also known as feed metering proportional valve. It is installed in the inlet position of the high-pressure oil pump and used to adjust the fuel supply and fuel pressure value, which is controlled by the ECU computer.

Fuel metering proportional valve in the control coil is not energized, fuel metering proportional valve is on, that is, we say the normally open solenoid valve, can provide the maximum flow of fuel to the pump. The ECU increases or decreases the oil volume by changing the intake area of the high-pressure oil pump through the pulse signal.

Here we can simply think of the fuel metering unit as an electromagnetic switch that controls the flow of oil to the pump. When the switch is not energized, the maximum amount of oil to the oil pump is opened. On the contrary, when the solenoid valve is in the zero oil supply position, the amount of oil to the oil pump should be zero.

Fuel metering unit is a precision element. If the maintenance of improper or poor quality filter element, often lead to the fuel water or impurities in too much to cause fuel metering spool wear or stuck, and then lead to the engine can not work properly.

Therefore, the normal and effective work of the electronic control system and scientific and reasonable maintenance is inseparable. The fuel metering unit is generally installed on the oil pump and is not allowed to be disassembled at will. In addition, the fuel metering units of different electric control systems are different, such as Bosch, denso and Delphi, so the specific electric control system needs to be solved.