43
Fuel ManageMent SySteM
79
High Pressure Pump Operation
• After being filtered at the engine mounted fuel filter, fuel
is directed to the high pressure fuel injection pump.
• Before fuel enters the Volume Control Valve (VCV) the
pressure is stepped up by the Internal Transfer Pump
(ITP). The ITP is located inside the high pressure fuel
injection pump and is driven by its main shaft.
• The VCV controls how much fuel enters the
three (3) main pump pistons.
• A portion of the fuel leaving the ITP is sent to a lubrication valve
which allows fuel to lubricate and cool the internal mechanical
components of the high pressure fuel injection pump.
• The high pressure fuel injection pump main shaft has an offset journal
that actuates each of the three (3) pistons as the shaft rotates.
• The offset journal of the main shaft utilizes a free-spinning
hub to make contact with the three (3) pistons.
1) ITP (internal transfer pump)
2) VCV (volume control valve)
3) High-Pressure Fuel Injection Pump Element
4) PCV (pressure control valve)
5) Inlet Pressure Control Valve
6) Lubrication Valve
7) Edge Filter
a) Fuel Inlet
b) High-Pressure Connection
c) Fuel Return
• The pistons start their compression stroke via the offset
journal and are returned to rest via spring pressure.
• The pistons receive fuel from the VCV through a one way check valve.
Fuel is drawn into the cylinder while the piston is returning to rest.
• The outlet check valve ball is closed while fuel is being drawn
in due to the suction (low pressure area) of the piston returning
to rest and the pressure exerted by the other two pistons.
• Once the piston starts its compression stroke, the inlet
check valve closes via spring and fuel pressure and the
outlet check valve opens due to increasing fuel pressure
forcing the check valve ball away from its seat.
• The pressure control valve (PCV) controls the pressure
in the system by restricting fuel flow to the return
line (pressure is the resistance to flow).
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