Fiat 1998 Marea Weekend, Service Manual

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Engine
Marea- Marea Weekend
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Fuel system 99 range
10.
The recirculation of the exhaust gases is only permitted at medium-low loads, when the air/fuel ratio is
very high and the operation of the engine is not adversely affected by the presence of inert gases in place
of the air.
The recirculation is controlled by the injection control unit (1) which, mainly according to the signals from
the accelerator pedal potentiometer, the rpm sensor and the engine coolant temperature senor, supplies an
output signal for the modulating solenoid valve (2).
The latter, connected to the atmosphere by means of a filter (3), transmits a lesser or greater vacuum, ac-
cording to the signal received, coming from the brake servo vacuum pump (5) to the EGR valve.
If the vacuum is sufficient, the valve (4) opens placing the exhaust manifold in contact with the inlet
manifold.
EGR MODULATING SOLENOID VALVE
The vacuum coming from the vacuum pump for the brake servo reaches the chamber (E) from the duct
(F) (case I) because the force of the spring (6) acts on the moving element (4) and the valve (5) allows
its flow.
The vacuum then enters the chamber (B), through the compensation port (D) and the surface of the disc
shuter (3).
When the forces acting on the disc (3) are balanced, the atmospheric pressure in the duct (A) enters the
chamber (B), moving the moving element downwards (case II), therefore the valve (5) shutter closes the
duct (F) and places chamber (E) in contact with chamber (C) at atmospheric pressure, decreasing the
vacuum in the duct (E).
I The decreased vacuum value or the increased
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