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GROUP 34
IGNITION SYSTEM
DESCRI PTION
The ignition.
sys,
t em is of the battery
ignition
type.
It
consists of the
fol1
lowing main
parts:
Ignition coil with advance engaging resistance, di-
stributor,
igni1
tion leads and spark plugs.
IGNITION COIL
The ignition coil and advance engaging resistance are
fitted on the bu lkhead, see Fig. 3-46. The function
of
the advanoe engaging
resistance
is to proteot the
ignition
coil from damage by
heating if
the
ignition
key is switched on and the engine
is
not running.
In order
to
raise
:
t he ignition
voltage at
the moment
starting takes
place,
the
advanoe engaging resistance
is
by-passe
d when the
starter
motor is
engaged. The
ignition
cOli
I
is
activa,
t ed directly by the battery vo lt-
age via
a
co ntact on the starter motor (see
wi
ring
d ia
gra
m). The advance e ngag
in
g resista nce has a
resistan
ce of 0.9 o hm.
VOLVO
1033 12
Fig
.
3-46.
Ignition
co
il and advan ce engaging
resistance
DISTRIBUTOR
The distributor is mounted on the left-hand side of
the engine, see Fig. 3-47, and is driven from
,
the
camshaft. The setting of the distributor in relation to
engine speed is regulated by a centrifugal governor
fitted under the breaker plate. Adjustment in relation
to loading is controlled by a vacuum regulator mount-
ed outside the distributor
(4;
Fig. 3-47).
2
Fig
.
3-47.
Distributor
1.
Primary conn ecti
o
n
wi
th capacit
o
r
2.
Lubricator
3.
Attaching bolt
4,
Vacuum r
egulato
r
VOLVO
1033
13
The vacuum regulator has two diaphragm
s
and is
constructed so that during engine braking or idling it
lowers the firing during the basic adjustment. When
engine brak,ing or idling
,
t akes place, the throttles
in the
carburettors
are closed so that
ther
e
is
no
vacuum in the connection from the carburettors (5, Fig
.
3-49) so that the return spring (60) presses back th
e
primary diaphragm (7) against the stop (8). The pull rod
(2) which is secu'red to the primary diaphragm (7)
trans-
mits the movements in the diaphragm to
;
t he breaker
plate.
If the vacuum in the connection from the intake
manifold (3) is sufficiently large, pull the secondary
diaphragm (4) from the stop (8) and this lowers the
firing during the basic adjustment.
During throtHing, diaphragm (7) is influenced by the
vacuum in the carburettors and takes over the re-
gulating function irrespective of the vacuum in the
intake manifoid.
3
:
19
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