Flow of fuel through the high-pressure pump

fig 1 32 Flow of fuel through the high pressure pump

1 Pressure control valve
2 Return bore
3 Feed bore – high-pressure chamber
4 Leak-off fuel – fuel injectors
5 Fuel return to fuel tank
6 High pressure channel to fuel rail
7 Fuel feed to the transfer pump

The low pressure fuel return has the following functions:
• Cools and lubricates the high-pressure pump by the internal return flow of the fuel, at low pressure, to the fuel tank,
• recirculates the leak-off fuel from the fuel injectors to the fuel tank.

When accelerating, fuel is delivered, unrestricted, to the high-pressure chamber. In addition, a proportion of the fuel is used to cool and lubricate the pump and flows through a calibrated return bore and then through the venturi back to the fuel tank.

The venturi in the fuel return works by the principle of a suction jet pump and produces a slight partial vacuum in the leak-off pipes, allowing the leaking oil to drain off optimally.

fig 1 33 Flow of fuel through the high pressure pump

1 Pressure control valve
2 Fuel injector fuel return bore
3 Feed bore – high-pressure chamber
4 Leak-off fuel – fuel injectors
5 Fuel return to fuel tank
6 Fuel feed to the transfer pump

When decelerating, the feed to the high-pressure chamber is closed by the fuel metering valve. As a result, the pressure in the feed bore rises.

When a specific maximum pressure has been reached, the pressure control valve, which is connected with the transfer pump via a bore, opens.

The some of the excess fuel flows back to the intake side of the transfer pump and via the venturi in the fuel return back to the fuel tank.

02. August 2018 by sam
Categories: Fuel System | Leave a comment

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