SsangYong Rexton. Manual - part 74

DI07-12

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FUEL SYSTEM

DI ENG SM - 2004.4

<Sectional view of transfer pump>

Y220_07018

FUEL TRANSFER LINE

Transfer Pump

Description

The transfer pump is the device to provide sufficient fuel to high fuel pressure line and is mechanical type feed pump that
is driven by timing chain linked to crankshaft. This mechanical type feed pump is subject to air inflow, therefore, a hand
priming pump is installed to fill fuel in Low fuel pressure(LP) circuit.

The transfer pump is included in the housing of the HP pump. The transfer pump is the volumetric blade type pump and
consists of the following components:

• A rotor turned by the shaft of the HP pump. The connection is provided by splines.

• An eccentric liner fixed to the housing of the HP pump by 6 Torx bolts. The liner is positioned by two off-set pins in

order to prevent any assembly errors.

• Four blades set at 90°. Each blade is held against the liner by a coil spring.

• The inlet and outlet orifice.

HP pump

<Sectional view of fuel pump>

Transfer pump

DI07-13

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EFFECTIVE DATE

AFFECTED VIN

FUEL SYSTEM

DI ENG SM - 2004.4

Y220_07026

Y220_07025

Principle of operation

Consider the chamber between the rotor, the liner and two successive blades (refer to above figure).

• When the chamber is in position 1, the volume of the chamber is minimal. The changes in volume according to the

angle of rotation of the rotor are small.

• The rotor makes a quarter turn clockwise. The previous chamber is now in position 2.

    The inlet orifice is uncovered. The volume contained in the chamber quickly rises. The pressure inside the chamber

drops sharply. Fuel is drawn into the chamber.

•  The rotor continues to rotate. It is now in position 3. The inlet and outlet orifices are now sealed off. The volume area

controlled by the rotor, the liner and the two blades is at the maximum. The changes in volume according to the
angle of rotation of the rotor are small.

• The rotor continues to rotate. It is finally in position 4. The outlet orifice is uncovered. The volume area controlled by

the rotor, the liner and the blades decreases quickly. The pressure inside the chamber rises sharply. The fuel is
expelled under pressure. The depression caused by the transfer pump’s rotation is sufficient to draw in diesel fuel
through the filter. The transfer pump is driven by the shaft of the HP pump, transfer pressure thus rises with engine
speed. A regulating valve allows the transfer pressure to be maintained at a practically constant level (about 6 bar)
throughout the whole range of engine operations by returning some of the fuel to the pump inlet.

   Regulating pressure

   Volume controlled

   Flow

  Intake capacity

6 bar

5.6 cm

3

/revolution

90  /h at 300 rpm pump

650  /h at 2,500 rpm pump

65 mbar at 100 rpm pump

Characteristics of the transfer pump

Fuel pump speed (rpm)

Fuel

pressure

(bar)

Housing

Rotor

Chamber

Blade

DI07-14

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AFFECTED VIN

FUEL SYSTEM

DI ENG SM - 2004.4

INLET METERING VALVE (IMV)

Y220_07027

Y220_07028

Y220_07029

Overview

The LP actuator, also called the inlet metering valve, is used
to control the rail pressure by regulating the amount of fuel
which is sent to the pumping element of the HP pump.

This actuator has two purposes:

1. Firstly, it allows the efficiency of the injection system to

be improved, since the HP pump only compresses the
amount of fuel necessary to maintain in the rail the level
of pressure required by the system as a function of the
engine’s operating conditions.

2. Secondary, it allows the temperature to be reduced in

the fuel tank. When the excess fuel is discharged into
the back leak circuit, the pressure reduction in the fluid
(from rail pressure down to atmospheric pressure) gives
off a large amount of heat. This leads to a temperature
rise in the fuel entering the tank. In order to prevent too
high a temperature being reached, it is necessary to limit
the amount of heat generated by the fuel pressure
reduction, by reducing the back leak flow. To reduce the
back leak flow, it is sufficient to adapt the flow of the HP
pump to the engine’s requirements throughout its
operating range.

IMV effect

without IMV
with IMV

without IMV
with IMV

Fuel temperature at

system backleak

Fuel T

emp.(°C

)

Torque (Nm)

Torque (Nm)

Rail pressure = 80 bar

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FUEL SYSTEM

DI ENG SM - 2004.4

Y220_07019

Composition of IMV

The IMV is located on the hydraulic head of the pump. It is fed with fuel by the transfer pump via two radial holes. A
cylindrical filter is fitted over the feed orifices of the IMV. This makes it possible to protect not only the LP actuator, but
also all the components of the injection system located downstream of the IMV.

The IMV consists of the following components:

• A piston held in the fully open position by a spring.

• A piston filter located at inlet.

• Two O-rings ensuring pressure tightness between the hydraulic head and the body of the IMV.

• A body provided with two radial inlet holes and an axial outlet hole.

• Coil

Filter

High pressure

Outlet hole

O-ring

Fuel

Transfer pump

Transfer pump

Solenoid

Fuel

Spring

Piston