Iveco daily euro 4, Repair Manual

Page: 171 / 1132

Figure 284
FUEL RECIRCULATION AND SUPPLY SYSTEM DIAGRAM
1. CP1 H high-pressure pump - 2. Pressure regulator - 3. Heated fuel filter with water separator - 4. Fuel delivery pipe to the filter - 5. Fuel return pipe to the tank - 6. Low-pressure pipe assembly - 7.
High-pressure delivery pipe to the hydraulic accumulator - 8. Pressure sensor - 9. Hydraulic accumulator - 10. Return pipe from the electric injectors to the low-pressure pipe assembly - 11.
High-pressure pipe between the hydraulic accumulator and the electric injectors - 12. Electric injectors.
high pressure
low pressure
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 composed 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 composed 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.
OPERATION
The pipes connected to the fuel filter support to the
low-pressure
pipe assembly are of the
quick-connect type.
Before fitting them, make sure the couplings and the
associated fittings on the mounting are clean.
NOTE
108338
F1A ENGINE
143
D
AILY
E
URO 4
Print 603.93.651 Base - March 2006