Describe the working of high pressure fuel pump.

Describe the working of high pressure fuel pump. 
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1 Answer

Answer :

Working:

Downward motion of plunger: The safety valve at the inlet opens if the pre-supply pressure of fuel exceeds 1.5 bars and fuel comes and fills the chamber till the plunger moves up to BDC.


Upward motion of plunger: - the upward motion of plunger closes the safety valve and increases the fuel pressure, this rise in pressure if it is more than the desired pressure then outlet (delivery) valve opens and pressurized fuel goes to common rail. Once the plunger reaches the TDC position then pressure falls and outlet valve closes.


Element shut-off valve –The pump flow can be varied with engine load; individual pistons of the pump are able to be shut down by using a solenoid to hold the intake valve of that piston open.


Delivery rate – The delivery rate of pressurized fuel during idling or part load condition is very

high but this can be reduced with help of pressure control valve.

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OR

The fuel inlet to the pump is controlled by the SCV (suction control valve) through the EDC

The rotation of the inner cam pushes the plunger inwards, so that it can pump the fuel.

Plunger outward movement is caused by the pressure of fuel feed pump. Fuel enters the pumping element chamber (intake stroke)

At BDC the check valve closes

The fuel in the chamber is pressurized by the plungers moving inward.

The delivery valve opens and the fuel passes to the common rail.

A constant pressure of about 1400 to 1600 bar is maintained in the common rail. 

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