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Iveco Daily. Manual - part 405

148

ELECTRIC/ELECTRONIC SYSTEM

AILY

Base - May 2004

These are located on the rail fuel outlet and their function is

to protect the engine or vehicle in the event of internal leaks

(for example, atomiser blocked open) and external leaks

(example: high pressure pipe damaged).
Under these circumstances they also allow, within certain

limits, the system to work through the components that are

still intact.
The passage of fuel from the rail to the injectors takes place

through the holes machined on the small diameter of the

piston.
Under normal conditions, the fuel pressure is exerted on both

sides of the piston, held n the open position by the spring.
In the event of a heavy loss of pressure downstream of the

limiter, the inlet pressure becomes preponderant and moves

the piston from the opposite side, obstructing the fuel outlet.

Pressure limiter

The pressure limiter (1500 bar) screwed in the rail, serves to

protect the system components in the event of a failure to the

pressure regulator on the pump.
If the pressure of the fuel in the rail exceeds 1500 bar the

piston is raised and the excess pressure is eliminated.

Fuel pressure sensor

This is fitted at the centre of the rail and measures the existing

fuel pressure in order to determine the injection pressure.
The injection pressure value is used as feedback for closed

loop pressure control and to determine the duration of the

electric command for injection.
It is connected to pins 6, 13 and 33 of connector A of the

control unit.
It is supplied at 5 Volt.

TECHNICAL VIEW OF COMPONENT AND LIMITER

CONNECTOR

PRESSURE LIMITER OPERATING GRAPH

1500 bar

0 bar

0.2V

0.5V

4.5V

4.8V

Minimum

1500 bar

0 bar

0.2V

4.8V

VOLTAGE

PRESSURE

Figure 156

Figure 157

ELECTRIC/ELECTRONIC SYSTEM

149

AILY

Injectors

The solenoid valve controls the lift of the atomiser needle.
On the fuel inlet union a filter protects the injector for

impurities. The injector is constructively the same as

conventional ones, except that there is no needle return

spring.
Access to the injectors is gained by releasing the side

soundproof cover from the cylinder head. The fuel recovery

pipe has a quick coupling.
The injector comprises two parts:
- actuator - atomiser composed of pressure rod (1), pin

(2) and nozzle (3)

- control solenoid valve comprising a coil (4) and drive

valve (5).

phase: rest position

The coil (4) is not activated and the shutter (6) is in the closed

position.
The same fuel pressure acts in both the control area (7) and

in the pressure chamber (8), but as the shutter (6) is closed,

the needle (2) cannot be raised.
2

phase: start of injection

The coil (4) is energised and causes the shutter (6) to move

upwards.
The fuel of the control volume (9) flows towards the backflow

duct (10) causing a drop in the pressure in the control area

(7).
At the same time, the pressure of the fuel in the pressure

chamber (8) causes the needle (2) to rise, resulting in fuel

injection to the cylinder.
3

phase: end of injection

The coil (4) is not activated and makes the shutter (6) return

to the closed position, which re-creates a balance of forces

that makes the needle (2) return to the closed position and

consequently end injection.
Injectors (78247)
The solenoid valve is of the N.C. type.
The injectors are connected individually to the control unit at

the following pins:
- A12 / A40 cylinder 1 injector
- A10 / A43 cylinder 2 injector
- A23 / A42 cylinder 3 injector
- A24 / A41 cylinder 4 injector

INJECTOR WIRING DIAGRAM AND CROSS SECTION

1. Pressure rod - 2. Needle - 3. Nozzle - 4. Coil - 5. Pilot

valve - 6. Ball shutter - 7. Control area - 8. Pressure

chamber - 9. Control volume - 10. Backflow duct -

11. Control duct - 12. Supply duct - 13. Electrical

connection - 14. High pressure fuel inlet - 15. Spring

5
6

Figure 158

150

ELECTRIC/ELECTRONIC SYSTEM

AILY

Base - May 2004

All the outlets, overpressure and backflows of the various

hydraulic components converge in this unit.
Part of them is made available to the thermal starter, while the

rest returns to the fuel tank.
In the unit there is a 2,3 mm diameter drain hole.
This hole regulates the whole outlet system to maintain a

constant counter pressure of 0,5 bar, which is indispensable

for correctly supplying the thermal starter and it ensures flow

rates which prevent overheating of the fuel.

FUEL OUTLET UNIT

1. Fuel outlet to tank - 2. Return from injectors -

3. Delivery to thermal starter - 4. Leading from high

pressure pump - 5. Arrival from filter

The calibrated hole is made in a union similar to

the other unions. In the event of work on the

system, take care not to fit another different

union in its place as this would cause serious

operating failures.

Figure 159

ELECTRIC/ELECTRONIC SYSTEM

151

AILY

Air flow meter

This component incorporates a temperature sensor and a

pressure sensor.
It is fitted on the engine intake manifold (Figure 162) and

measures the maximum flow rate of the intake air which is

used to accurately calculate the amount of fuel to be injected

at each cycle.
It is connected to the control unit on pins A2 / A3 / A19 / A34.
Pin 1 sensor - Pin A19 ECU -

earth -

Pin 2 sensor - Pin A2 ECU

temperature signal

Pin 3 sensor - Pin A3 ECU

5V - supply

Pin 4 sensor - Pin A34 ECU

0 ÷ 5V

pressure signal -

Course of sensor in relation to the temperature:

Temperature

Resistance

- 40 °C

48.50 kOhm

- 20 °C

15.67 kOhm

0 °C

5.86 kOhm

20 °C

2.50 kOhm

40 °C

1.17 kOhm

60 °C

0.59 kOhm

80 °C

0.32 kOhm

100 °C

0.18 kOhm

120 °C

0.11 kOhm

Course of sensor in relation to the pressure:
See graph opposite.

AIR FLOW METER

1. Air flow meter location

AIR FLOW METER CONNECTION

2.5 bar

0.2 bar

0.4V

4.65V

VOLTAGE

ABSOLUTE PRESSURE

AIR FLOW METER OPERATING GRAPH

Figure 160

Figure 161

Figure 162

Figure 163

8660

003323t

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