Ford Transit 2002 Owner's Manual page 845

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The storage pressure required for the common rail is created in the high pressure chamber
of the high pressure pump.
The system operates according to the radial piston principle and consists of an inlet and
outlet valve, both equipped with a return valve, two pump pistons with rollers and roller
shoes and a cam ring. The cam ring is part of the drive shaft.
Filling the high pressure chamber
If the transfer pressure exceeds the internal pressure of the high pressure chamber, the
inlet valve opens. Fuel flows into the high pressure chamber and presses the pump piston
and the roller shoe outwards against the cam track of the cam ring (cams run down from
the roller of the pump piston.)
The outlet valve remains closed because of the higher pressure in the high pressure
channel which is behind it
Item Part Number
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Creation of high pressure in the high pressure chamber
When a cam begins to run onto the roller shoe of the pump piston, the piston moves
towards the centre of the high pressure chamber. As this occurs, the supply pressure of
the pump piston exceeds the transfer pressure and the inlet valve is closed.
As soon as the pressure in the high pressure chamber exceeds the pressure in the high
pressure channel, the outlet valve opens and fuel is supplied to the common rail through
the high pressure connection.
The supply phase continues until the roller of the roller shoe reaches the peak of the
curve of the cam and the pump pistons have moved the maximum supply travel.
At this moment the pressure in the high pressure chamber drops below that in the high
pressure channel. Because of the higher pressure in the high pressure channel, the outlet
valve is closed again and the supply of fuel is therefore stopped.
The amount of fuel supplied depends on the cross-section of the opening of the fuel
metering valve.
Roller and roller shoe
(outlet 3
valve
4 High pressure chamber
closed)
5 Exhaust valve
Pump piston
Description
Intake valve
Cam ring
Roller and roller shoe
High pressure chamber
Exhaust valve
To high pressure channel/high pressure connection
Pump piston
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