Fiat 1998 Marea Weekend, Service Manual

Page: 403 / 846

Marea-Marea
Weekend
ft^ft
99 range
JTD
Engine
Fuel system
1. Pressure rod
2. Pin
3. Jet
4. Coil
5. Valve
6. Ball shutter
7. Control area
8. Supply volume
9. Control volume
10. Fuel outlet connector (low pressure)
11. Control duct
12. Supply duct
13. Electrical connection
14. Fuel inlet connector (high pressure)
15. Spring
10.
INJECTORS
The injectors, fitted on the cylinder head, are
the electro-magnetic type operated directly by
the injection control unit.
The injector have a high pressure supply duct
and a recirculation pipe at ambient pressure;
the supply duct is connected to the supply
manifold (rail) with pipes designed to with-
stand high operating pressures.
The injector can be divided into two sections:
- actuator/nozzle consisting of a pressure rod
(1), pin (2) and jet (3);
- solenoid valve consisting of a coil (4) and
valve (5).
Operation
The operation of the injector can be divided
into three stages:
1. rest position
The coil (4) is de-energized and the shutter
(6) is in the closed position and does not al-
low the introduction of fuel into the cylinder:
Fc > Fa where Fc is the force produced by the
pressure acting on the control area (7) of the
pressure rod (1) and Fa is the force due to the
pressure acting in the supply volume (8).
2. start of injection
The coil (4) is energized and causes the lifting
of the shutter (6). The fuel flows from the
control volume (9) to the return manifold
causing a decrease in pressure at the control
area (7). At the same time, the line pressure
passes through the supply duct (12) exerting a
force in the supply volume (8) Fa > Fc causing
the lifting of the pin (2) with the consequent
introduction of fuel into the cylinders.
3. end of injection
The coil (4) is de-energized and returns the
shutter (6) to the closed position recreating an
equilibrium which returns the pin (2) to a
closed position and consequently ends the in-
jection.
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