CI{APTER 3
THE
IGNITION
SYSTEM
3:1
Description
3:2
Routine
maintenance
3:3
lgnition
faults
3:4
Timing
the
ignition
3:1 Description
AII cars covered bv this manual
use
Ducellier
or SEV
distributors,
which incorporate
a centrifugal advance and
a
vacuum
advance mechanism.
The
vacuum
unit, containing a spring-loaded
dia-
phragm
is linked
to the contact breaker moving
plate,
and
the
vacuum
side of the unit is
connected by a
pipe
to the
carburetter.
Under
part
throttle conditions,
the depression
in the manifold actuates the contact
breaker
plate
to
advance the
ignition
timing.'During
acceleration, when
the engine is under
load,
the
depression
is
not sufficient
to actuate the contact
breaker
plate
against the tension
oÍ the diaphragm, so that the
plate
is held in
the
retarded
posrtron.
The
centrifugal advance mechanism consists of
a cam
actuated by two spring-loaded weights. As
the speed of
the engine increases, the
weights swing
outwards
against the
pull
of the springs. This moves
the cam in
an
anti-clockwise direction, causing the
contact breaker
pornts
to
open
earlier
and advance
the
timing. The
distributor
can be seen in
FIG 3
:1.
The
coil and the condenser
(capacitor)
are also
made
bv Ducellier
or
SEV.
For
sparking
plugs
see
Section 3
:5.
P404
3:5 Spark
plugs
3:6
Testing the
ignition
syltem
3:7
Fault diagnosis
3
:2 Routine maintenance
Refer
to FIG 3:2 and
remove ihe distributor cap.
Pull
the
rotor
squarely
off the
end
of
the mainshaft and cam.
Apply
a few drops of
engine oil to the
felt
pad
in the end
of
the cam under
the
rotor. Take
great
cale
to
avoid
oil
coming
into contact
with the contact breaker
plate
or the
oornts.
Lightly
smear
the cam with
petroleum
jelly.
Adjusting the contact breaker
points:
Refer to FIG 3:3,
and
with the
distributor cap and
rotor removed, slacken the
locking
screw V.
Move
the eccentric E, in the
appropriate direction to
obtain
the correct
gap
through the displacement
of
the
support
S,
which
pivots
about the axis
pin
A.
Set
the
gap
to
.5
mm
(.02
inch).
Retighten the screw V, and
recheck
the
gap.
The
gap
must be set and
measured
when the cam
peak
is
central-
ized
on the contact arm.
lf the contact breaker
points
are dirty or
pitted
they
must be cleaned by
polishing
them with
a
fine
carbor-
undum stone,
taking care to keep the Íaces Ílat
aod
square.
Afterwards,
wipe away all traces of dust with a
non-fluffv cloth
moistehed in fuel.
31
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