Iveco EuroCargo (12 to 26 t). Manual

78671

Figure 203

1. Injector - 2. Common Rail - 3. Pressure limiter for fuel return - 4. Rail overpressure valve - 5. Prefilter assembled on

chassis - 6. High-pressure pump - 7. Mechanical rotor pump - 8. Fuel filter.

The Common Rail system has a special pump that continuously keeps fuel at high pressure, independently from stroke and
cylinder that has to receive the injection and accumulates fuel in a common duct for all injectors.

Therefore, fuel at the injection pressure computed by the ECU is always available at the injectors inlet.

When an injector solenoid valve is energised by the electronic control unit, the injection of fuel directly taken from rail takes
place in the related cylinder.

The feed system is implemented by a low-pressure circuit and a high-pressure circuit.

The high-pressure circuit is composed of the following pipings:

- piping connecting high-pressure pump outlet to rail;

- pipings supplying injectors from rail.

The low-pressure circuit is composed of the following pipings:

- fuel suction piping from tank to prefilter;

- pipings supplying the mechanical supply pump through the control unit heat exchanger, manual priming pump and prefilter;

- pipings supplying the high-pressure pump through the fuel filter.

The fuel draining circuit from rail and from injectors and the high-pressure pump cooling circuit complete the system.

FEED SYSTEM

High Pressure

Low Pressure

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ENGINE F4 AE 0481

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Figure 204

This Common Rail injection system, with CP3 pump, is
mostly different from the one adopted on the Daily range
with CP1 pump due to the different pressure regulator
position and due to the gear supply pump.

The pressure regulator, placed upstream of the high-pressure
pump, adjusts the fuel flow that is necessary on the
low-pressure system. Afterwards, the high-pressure pump
takes care of supplying the rail properly. This arrangement, by
pressurising the necessary fuel only, improves the energetic
efficiency and limits fuel heating in the system.

Function of the pressure relief valve (2), assembled on the
high-pressure pump, is keeping the pressure, at the pressure
regulator inlet, constant at 5 bars, independently from the
efficiency of the fuel filter and of the system set upstream.

The pressure relief valve (2) intervention brings about a fuel
flow increase in the high-pressure pump cooling circuit,
through inlet and drain piping (16) from piping (8).

The pressure relief valve housed on the cylinder head,
assembled on injector return (3), limits the fuel return flow
from injectors at a pressure of 1.3 to 2 bars.

Two by-pass valves are placed in parallel with the mechanical
supply pump.

The by-pass valve (18) allows fuel to flow from mechanical
pump outlet to its inlet, when the fuel filter inlet pressure
exceeds the allowed threshold value.

The by-pass valve (17) allows filling the supply system
through the manual priming pump (10).

1. High-pressure pump. — 2. Pressure relief valve on high-pressure pump, 5 bars. — 3. Pressure relief valve assembled on fuel return from injectors, 1.3 to 2 bars. — 4. Rail overpressure valve.

— 5. Common Rail. — 6. Pressure sensor. — 7. Injector. — 8. Return piping. — 9. Control unit heat exchanger. — 10. Mechanical priming pump. — 11. Prefilter assembled on chassis. — 12. Fuel

tank. — 13. Mechanical supply pump. — 14. Fuel filter. — 15. Pressure regulator. — 16. High-pressure pump cooling piping. — 17. By-pass valve. — 18. By-pass valve.

EXHAUST

INTAKE (LOW PRESSURE)

HIGH-PRESSURE (LOW-PRESSURE) PUMP SUPPLY

HIGH PRESSURE

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70495

Figure 205

Figure 206

The fuel filter is of the high water separation type, is
assembled on the right side of the vehicle chassis, and has the
sensor (4) for detecting water in fuel placed on the cartridge
(3) base.

Manual priming pump (5) and air bleeding screw (2) from
system are placed on filter support.

The presence of condensate into filter is signalled by sensor
(4) when a warning light on the instrument panel is lit.

FUEL PREFILTER

1. Fuel filter support - 2. Fuel temperature sensor -

3. Electric fuel heater - 4. Fuel filter - 5. Heater connector.

It is placed on engine block in the circuit between supply
pump and high-pressure pump (CP3).

Cartridge filtering degree: 4 microns, Pressure delta 2 bars.

The following are placed on the support: fuel temperature
sensor and heater resistances.

Fuel temperature, signalled by the related sensor to EDC7
control unit, allows a very accurate computation of the fuel
flow-rate to be injected into the cylinders.

The electric heater is activated when fuel temperature is
below 5

°C.

FUEL FILTER

If the warning light is on, it is necessary to im-
mediately operate to remove its cause; the common
rail system components are quickly damaged by the
presence of water or impurities in the fuel.

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MECHANICAL SUPPLY PUMP

Gear pump, fitted on the rear side of the high pressure pump
and used to supply it.
It is controlled by high pressure pump shaft

Normal operating conditions

Figure 207

72592

A Fuel inlet from tank, B fuel outlet to filter, 1-2 by-pass valves
in close position

Overpressure condition at outlet

Figure 208

72593

The by-pass valve (1) cuts in when overpressure is generated
at outlet B. The existing pressure, overcoming valve spring (1)
elastic strength, makes inlet and outlet communicating
through duct (2).

Figure 209

Drain conditions

72594

The by-pass valve (2) cuts in when, with engine off, the fuel
system shall be filled through the priming pump. In this
situation the by-pass valve (1) stays closed whereas by-pass
valve (2) opens due to inlet pressure, and fuel is drained out
through B.

The mechanical supply pump cannot be replaced
individually, therefore it cannot be removed from the
high pressure pump.

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Iveco EuroCargo (12 to 26 t). Manual - part 26