Fiat 1998 Marea Weekend, Service Manual

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Marea-Marea Weekend ®
1*
Engine
1998 range F u e l s y s t e m
10.
IGNITION MANAGEMENT
The ignition circuit is static inductive discharge type, i.e. a high tension distributor with power modules
located inside the injection-ignition control unit.
The system comprises two high tension twin outlet coils combined in a single container and connected
directly to the spark plugs.
The primary winding of each coil is connected to the power relay (i.e. supplied by battery voltage) and
pins of the ECU for connection to earth.
Once the start-up stage is over, the ECU implements a base pulse constant taken from a specific map in
accordance with the following input parameters:
- engine rotating speed (rpm),
- absolute pressure reading (mmhg) obtained in intake manifold.
This advance setting is corrected according to temperature.
The advance angle is also subject to correction under the following conditions:
- during start-up;
- during transient stages of acceleration and over-run.
- during cut-off.
- to stabilise idle speed
- when knock is present
- when required by the automatic transmission ECU (speed change).
For the ignition system to work efficiently, the ECU must recognise the signal configuration.
A. Rpm sensor signal
B. Power control
C. Current running through coil pri-
mary winding
a. Ignition advance with reference
to cylinder TDC
The gap or change in signal generated by the lack of two teeth on the phonic wheel, more specifically
between the 58th and 1st tooth (known also as the synchronism tooth) which occurs each time the
crankshaft pulley turns is a reference signal which allows the ECU recognition 114° in advance of TDC
of piston pair 1 -4 in correspondence to falling front of 20th tooth.
Once the ECU (see following page) has received the correct T.D.C. signal configuration, it establishes
the point at which conduction (supply) to primary circuits of coils (6) begins through internal power
module (5).
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