Iveco Daily. Manual — part 35
ENGINES 8140.43R/B/S/N
122
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AILY
Base - May 2004
When the pressure of the fuel exceeds the setting of the
pressure relief valve (1550 bar) it overcomes the reaction of
the spring (2) and, by shifting the plunger (1), discharges the
fuel into the low pressure - recovery circuit.
52177
Figure 253
FUEL SUPPLY AND RECIRCULATION SYSTEM DIAGRAM
1. Thermostart glow plug - 2. Thermostart solenoid valve - 3. Electro-injector - 4. Hydraulic accumulator (rail) - 5. 3rd pumping element exclusion solenoid valve -
6. High-pressure pump - 7. Fuel filter - 8. Motor pump - 9. Pre-filter - 10. Tank - 11. Pressure control valve - 12. Fitting - 13. Pressure relief valve - 14. Flow limiters.
61982
Figure 254
542025
542026
Fuel recirculation and supply
system
The supply system is divided into a low-pressure circuit and
a high-pressure circuit.
The low-pressure circuit comprises: pre-filter pipes, motor
pump, fuel filter, fuel outlets, recirculation pipes, thermostart
solenoid valve and thermostart glow plug.
The excess fuel of the high-pressure pump is partly used for
lubricating and cooling the pump and with the excess fuel from
the electro-injectors supplies the thermostart.
The excess fuel from the hydraulic components flow into the
outlets.
The union fixing the outlet coupling and the pressure relief
valve of the hydraulic accumulator contains a calibrated hole
whose purpose is to keep an overpressure of 0.5 bar in the
starter heater circuit.
The system does not require air bleeding.
The low pressure supply pipes, except for the recirculation
pipes, are fast coupling ones.
1
2
High pressure
Low pressure
Thermostart supply
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Pressure relief valve
ENGINES 8140.43R/B/S/N
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Figure 255
Operation
Electro-injector operation can be broken down into three
phases:
—
”rest position”
Coil (4) is de-energised, and shutter (6) is in closing position
and prevents fuel from being introduced into the cylinder, Fc
> Fa (Fc: caused by fuel pressure acting on control area (7) of
rod (1); Fa: caused by line pressure acting on pressure
chamber (8).
—
”start of injection”
The coil (4) is energized and causes the shutter (6) to rise.
The fuel of the control volume (9) flows off towards the return
manifold (10) causing a drop in pressure in the control area
(7).
At the same time, line pressure through feed duct (12) applies
a force Fa > Fc in pressure chamber (8) lifting peg (2), with fuel
being consequently introduced into cylinders.
—
”end of injection”
The coil (4) is de-energized and makes the shutter (6) return
to its closed position. This recreates such a balance in the
forces as to make the pin (2) return to its closed position and
consequently end injection.
Injector level
The injector level is the set of characteristics of the amount of
fuel injected in relation to the duration of the electrical signal
at different pressures of injection. Accurate knowledge of
these characteristics is of fundamental importance in
determining the necessary electrical signal to inject the desired
quantity of fuel.
Experimental measurements
The injector level can be measured:
—
on the injector test bench;
—
on the engine on the bench.
In both cases an injection pressure is established and the
injectors are actuated (in the case of the test bench it is also
possible to measure one injector at a time) with an electrical
signal of fixed frequency (NG) and duration (ET).
On the injector test bench, the injected quantity is measured
by directly accumulating, for a set time, the fuel in graduated
burettes, then dividing the accumulated quantity by the
number of injections.
On the engine on the bench, the injected quantity (QCARB)
is measured indirectly by the consumption of fuel, generally
measured with a gravimeter and expressed in kg/h. The
measurement should be made for a sufficiently long time so
as to average out errors.
However, it is necessary that throughout the measurement
the speed of the engine and the injection pressure remain
constant. In addition, all recirculation (pump, pressure
regulator, injectors) must be put back into the circuit
downstream from the meter so the measurement is not
changed.
1. Pressure rod - 2. Pin - 3. Nozzle - 4. Coil -
5. Pilot valve - 6. Ball shutter - 7. Control area -
8. Pressure chamber - 9. Control pipe - 10. Low-pressure
fuel return - 11. Control pipe - 12. Supply pipe -
13. Electrical connection - 14. High-pressure fuel inlet fitting
- 15. Spring
Electric injectors feed at high pressure (up to 1350 bar) and
recirculate at atmospheric pressure; recirculation is necessary
for diesel oil used for pilot valve operation.
The temperature of the diesel put back into circulation by the
electro-injector can get very high (approximately 120
°C).
The head of the electro-injector has a fitting for the electrical
connector.
They are mounted on the cylinder head and operated by the
injection control unit.
The electro-injector can be divided into two parts:
—
actuator/jet composed of pressure rod (1), pin (2) and
nozzle (3)
—
control solenoid valve composed of coil (4) and pilot val-
ve (5).
775010
ELECTRO-INJECTORS
50704
ENGINES 8140.43R/B/S/N
125
D
AILY
Base - May 2004
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