Fiat 1998 Marea Service Manual page 242

Engine
Fuel system
10.
1
28 B
38 B
mam
mm
4 1
28
3
10B
19B
mm
"060606
3 2
Marea- Marea Weekend
IGNITION COILS
The ignition circuit is the inductive discharge
static advance type, where the high tension is
supplied by two twin outlet coils fitted laterally
to the cylinder head.
The coils used are the closed magnetic circuit
type, with windings in a plastic container im-
mersed in epoxide resin. Each coil is connected
to the two spark plugs by means of high ten-
sion leads with high dielectric properties.
In this type of coil the current in the secondary
winding (discharge current) always has the
same polarity, therefore one terminal of the cir-
cuit is positive and the other negative.
This fact implies that the discharge current in
the secondary winding is always flowing in the
same direction and therefore the sparks for the
two cylinders connected to the coil strike in
the opposite way:
- in the spark plug with the positive centre
electrode, the spark strikes from the earth
electrode to the centre one;
- in the spark plug with the negative centre
electrode, the spark strikes from the centre
electrode to the earth one;
As a result, the wear of the electrodes between
the two spark plugs is different.
Since the intensity of the spark depends on the
resistance between the electrodes (dielectric),
whilst the spark in the cylinder in the cross-
over stage is weak (lost spark) on account of
the almost atmospheric pressure in the cham-
ber, the spark in the cylinder at the end of the
compression stroke is intense (working spark)
on account of the high pressure in the cham-
ber.
Connector wiring
ft
16M
99 range
Print n° 506.763/14