Fiat 1996 Brava Service Manual page 362

Bravo-Brava $fy™ Engine
98 range Fuel system
10.
I I INJECTORS
8
^V-- 3
P4A13KJ01
1. Pressure rod
2. Pin
3. Jet
4. Coil
5. Valve
6. Shutter with ball
7. Control area
8. Supply volume
9. Control volume
10. Fuel outlet connector (low pressure)
11. Control manifold
12. Supply manifold
13. Electrical connection
14. Fuel inlet connector (high pressure)
15. Spring
The injectors, fitted on the cylinder head, are the
electro-magnetic type, operated directly by the
injection control unit.
The injectors are equipped with 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
withstand the high operating pressures.
The injector can be divided into two parts:
- 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 injectors can be divided in­
to three stages:
1. rest position
The coil (4) is de-energized and the shutter (6)
is in the closed position and does not allow the
introduction of fuel into the cylinder: F o F a
where Fc is the force produced by the pressure
which acts on the control area (7) of the pres­
sure rod (1) and Fa is the force produced by the
pressure acting on the supply volume (8).
2. start of injection
The coil (4) is enerigzed and raises the shutter
(6). The fuel flows from the control volume (9)
to the return manifold causing a decrease in
pressure in the control area (7). At the same
time, the line pressure through the supply mani­
fold (12) exerts a force Fa>Fc on the supply
volume (8) raising the pin (2) with the conse­
quent 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 which restores
a balance which returns the pin (2) to the
closed position and consequently the injection
ends.
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