Filter
Top Products
Tractors.
Lawn
and
Garden
- 110
and
112
Electrical
System
40
SM
-2059-
(Apr-67)
Ignition
System
10-1
Group
10
IGNITION
SYS
TEM
GENERAL
INFORMATION
The
ignition
system
has
two
Circuits;
primary
and
secondary.
The
primary
is
a
low-voltage
circuit
and
the
secondary
is
a
high-voltage
cir-
cuit.
The
primary
circuit
consists
of
the
battery
,
a
solenoid.
a
switch,
breaker
points,
a
condenser
and
necessary
wiring
to
eonnect
these
units.
The
secondary
circuit
consists
of
the
secondary
wind-
ing
in
the
coil,
spark
plug
and
high
tension
wire
to
connect
coil
secondary
circuit
to
the
spark
plug.
When
the
breaker
points
are
closed,
the
pri-
mary
or
low-voltage
current
flows
from
the
bat-
tery
through
the
ignition
switch
to
the
primary
windings
in
the
coil.
then
to
ground
through
the
closed
breaker
points.
When
the
breaker
points
open
,
the
magnetic
field
build-up
in
the
primary
windings
of
the
coil
moves
through
the
secondary
windings
of
the
coil
inducing
high-voltage
cur-
rent.
This
high-voltage
current
is
distributed
to
the
spark
plug
to
ignite
the
fuel-air
mixture
in
the
combustion
chamber.
IGNITION
COIL
I U
II
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Fig.
I-Ignition
Coil
The
igniti(m
coil
is
a
pulse
transformer
that
transfor
ms
or
steps
up
the
low
hattery
or
gen-
erator
vo
ltage
to
the
high-voltage
necessary
to
ignite
the
fuel-air
mixture
at
the
g::t
pof
tl1P
spark
plug.
Litho
in
U.S.A.
The
ignition
coil
contains
three
basic
parts:
a
primary
winding
consisting
of a
few
hundred
turns
of
relatively
heavy
wire;
a
secondary
wind-
ing
consisting
of
many
thousand
turns
of ve
ry
fine
wire
and
laminated
soft
iron
which
serves
to
con-
centrate
th
e
magnetic
field.
The
primary
winding
is
assembled
around
the
outside
of
the
secondary
winding
and
the
laminated
iron
provides
both
a
core
and
outside
shell
about
both
the
windings.
These
three
units
are
placed
in
the
coil
case
and
immersed
in
oil.
The
coil
cap
with
its
necessary
attachments
to
the
windings
completes
the
entire
coil.
When
the
primary
circuit
is
energized
(the
breaker
pOints
are
closed),
a
magnetic
field
is
built
up
around
both
the
primary
and
secondary
coils.
When
the
primary
circuit
is
de-energized
(the
breaker
points
are
opened),
the
magn
t
ic
field
collapses
about
the
coils
inducing
a
volt
a
ge
within
both
of
the
coils.
The
voltage
developed
within
the
primary
coil
(possibly
250
volts)
is
absorbed
and
dissipated
by
the
condenser.
The
voltage
developed
within
the
seeondary
Guil
(pos-
sibly
25,000
volts
or
more)
is
distributed
to
the
spark
plug
for
igniting
the
fuel-air
mixture
with-
in
the
cylinder.
SPARK
PLUG
A
spark
plug
consists
mainly
of
two
elec-
trodes
separated
from
each
other
by a
specific
gap.
The
side
electrode
is
connected
to th
s
hell
of
the
spark
plug.
The
center
electrode
is
com-
pletely
insulated
from
the
shell.
The
high-volt-
age.
produced
in
the
secondary
windin
g of
the
coil,
is
applied
to
the
center
electrode
and
caus
es
a
spark
to
jump
the
c;ap
to
the
side
electrode.
This
spark,
inside
the
cylinder,
ignites
the
fuel-
air
mixture
and
starts
the
combustion
pro
ce
ss
in
the
combustion
chamber
of
the
cylinder.
Tbe
g;
ap
spacing
between
electrodes
is
critical
for
e
fficient
en~ine
operation.
Corr
e t
sp
ar
k
plug
~ap
affects
the
entire
range
of
performance
of
the
engin
e ;
startin
'
~:.
idling.
acceler
at ing.
power
and
top
speed.