Fiat 1998 Marea Weekend, Service Manual

Page: 393 / 846

Marea-Marea Weekend®™®™
99 range
Engine
Fuel system
10.
FUEL SYSTEM
INTRODUCTION
The Marea and Marea Weekend 1.9 JTD and 2.4 JTD vehicles are equipped with a 4 cylinder in line 1910
cc turbodiesel engine for the former and a 5 cylinder lin line 2387 cc turbodiesel engine for the latter, both
with two valves per cylinder, a counter-balance shaft, an overhead camshaft, supercharged by a turbo-
charger and intercooler and with electronic fuel injection.
The fuel system ensures the correct operation of the engine and can be summarized in the following cir-
cuits:
- fuel supply circuit with Common Rail type injection;
- air supply circuit;
- exhaust circuit;
- oil vapour recirculation circuit from the crankcase;
- exhaust gas recirculation circuit (EGR).
The optimum operation of the various "circuits" which make up the fuel system is achieved through an
electronic control system managed by a specific control unit.
The main feature of the fuel system is the Common Rail type fuel injection. The Common Rail system in-
volves electronic injection at high pressure for direct injection fast diesel engines.
The main features of the Common Rail system are:
- availability of high injection pressures (up to 1350 bar);
- possibility of modulating these pressures (from a minimum of 150 bar up to a maximum of 1350 bar)
independently of the engine rotation speed and load.;
- capacity for operate at high engine speeds (up to 6000 rpm);
- precision injection control (advance and duration of injection);
- reduction in consumption;
- reduction in emissions.
FUEL SYSTEM MANAGEMENT STRATEGIES
The control unit memory contains the management programme (software) which consists of a series of
strategies, each of which manages a precise system control function.
By using the information supplied by the various sensors (input), each strategy processes a series of pa-
rameters, based on data maps stored in special areas of the control unit memory and then controls the
system actuators (output) which are the devices which allow the engine to run.
The main aim of the management strategies is to determine the exact quantity of fuel which should be in-
jected into the cylinders with the timing (injection advance) and pressure so that the engine behaviour is
optimum in terms of power, consumption, fumes, emissions and driveability.
The main system management strategies are basically the following:
- controlling the quantity of fuel injected; - controlling the temperature of the engine
- controlling the injection advance; coolant;
- controlling the injection pressure; - controlling the heater plugs;
- controlling the auxiliary electric fuel pump; - controlling the exhaust fumes;
- controlling the injection during deceleration - controlling the exhaust gas recirculation
(cut-off); (EGR);
- controlling the idle speed; - controlling the engagement of the climate
- controlling the restriction of the maximum control system;
speed; - controlling the engine immobilizer function
- controlling the restriction of the maximum (Fiat CODE);
torque; - autodiagnosis.
- controlling the fuel temperature;
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