Iveco daily euro 4, Repair Manual

Page: 326 / 1132

112218
Figure 327
OPERATION
In this injection system, the pressure regulator, located
upstream from the high-pressure pump, governs the flow of
fuel needed in the low-pressure system. Afterwards, the
high-pressure
pump correctly supplies the hydraulic
accumulator.
This solution, pressurizing solely the necessary fuel, improves
the energy efficiency and limits heating the fuel in the system.
The relief valve fitted on the high-pressure pump has the
function of keeping the pressure, at the pressure regulator
inlet, constant at 5 bars; irrespective of the efficiency of the fuel
filter and of the system upstream. The action of the relief valve
causes an increase in the flow of fuel in the high-pressure pump
cooling circuit.
The high-pressure pump continually keeps the fuel at the
working pressure, irrespective of the timing and the cylinder
that is to receive the injection and accumulates it in a duct
common to all the electro-injectors.
At the electro-injector inlet, there is therefore always fuel at
the injection pressure calculated by the electronic control unit.
When the solenoid valve of an electro-injector is energized by
the electronic control unit, fuel taken straight from the
hydraulic accumulator gets injected into the relevant cylinder.
The hydraulic system is made out of a low-pressure fuel
recirculation circuit and a high-pressure circuit.
The high-pressure circuit is made up of the following pipes:
- pipe connecting the high-pressure pump outlet to the
hydraulic accumulator (rail);
- hydraulic accumulator (rail);
- pipes feeding the electric injectors from the hydraulic
accumulator.
The low-pressure circuit is made up of the following pipes:
- fuel intake pipe from the tank to the filter;
- pipe assembly made up of the following:
- feed pipe from the fuel filter to the high-pressure pump;
- fuel return pipe from the high-pressure pump to the tank;
- fuel exhaust pipe from the injectors to the fuel return pipe
to the tank.
According to the high performance of this hydraulic system,
for reasons of safety it is necessary to:
- avoid
connecting high-pressure pipe fittings with
approximate tightening;
- avoid disconnecting the high-pressure pipes with the engine
running (NEVER try bleeding, which is both pointless and
dangerous).
The integrity of the low-pressure circuit is also essential for the
system to work properly; it is therefore necessary to avoid all
manipulation and modifications and act only in the event of
leakage.
HYDRAULIC SYSTEM
The hydraulic system is composed of:
- tank
- fuel pre-filter
- electric supply pump
- fuel filter
- high pressure supply pump with supply pump built
inpressure regulator
- manifold (rail)
- electro-injectors
- supply pipes and fuel recirculation
Fuel pipes
1. Quick-connect coupling for high-pressure pump feed
pipe - 2. Quick-connect coupling for feed pipe -
3. Fuel filter support
Due to the very high pressure existing within this
hydraulic system, the following precautions shall be
taken for safety reasons:
-
avoid connecting the high-pressure pipe fittings
by means of makeshift fasteners: tighten them
to the specified torque;
- avoid disconnecting the high-pressure pipes
when the engine is running (DO NOT make
any attempt at draining: this is absolutely
useless and dangerous!).
To ensure correct operation of the system, it is
essential that the low-pressure circuit is intact.
Therefore,
any modification or attempt at
tampering shall be avoided, and corrective actions
shall be taken immediately in case of leaks.
In the event that fuel pipes (1 and 2) are
disconnected from support (3), make sure, when
reattaching the pipes, that their respective fittings
are fully clean.
Such precautions shall be taken to avoid detective
sealing, with resulting fuel leaks.
NOTE
298
F1C ENGINE D
AILY
E
URO
4
Base - March 2006 Print 603.93.651