Fiat 1996 Brava Service Manual page 279

Engine
Fuel system
10.
J
10B
19B
_n n_
1 2
IT—l
3
L
28B
38B
Bravo-Brava @t 16v
98 range
IGNITION COILS
The ignition circuit is the inductive discharge,
static advance type where the high tension is
provided from two twin outlet coils fitted at
the side of the cylinder head.
The coils used are the closed magnetic circuit
type with the windings in a plastic container
immersed in epoxide resin. Each coil is con­
nected to the two spark plugs by means of
high tension leads with dielectric properties.
In this type of coil the current in the sec­
ondary winding (discharge current) always
has the same polarity: therefore one end of
the circuit has a positive potential and the
other a negative potential.
This implies that the discharge current in the
secondary winding always flows 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 towards the centre one;
- in the spark plug with the negative centre
electrode the spark strikes from the centre
electrode towards the earth one.
As a result the wear of the electrodes be­
tween the two spark plugs in question is dif­
ferent.
Since the intensity of the spark depends on
the resistance between the electrodes (di­
electric), whilst the spark in the cylinder in
the cross-over stage is weak (lost spark), at
alsmot atmospheric pressure in the cylinder
at the end of the compression stroke, the
spark is intense (working spark) by virtue of
the high pressure in the chamber.
Wiring connector
28
Print no. 506.670/16