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Top Products
40
Electrical
S~'stem
Tractors,
Lawn
and
Garden
-
110
and
112
10-4
Ignition
System
SM-2059-
(Apr-67)
SPARK
PLUG
ANAL
YSIS-Contlnued
Fig
. 8
-Heat
Shock
Failu
re
Heat
shock
is
a
common
cause
of
broken
and
cracked
insulator
tips.
Incorrect
ignition
timing
and
a
poor
grade
fuel
are
usually
responsible
for
heat
shock
failt!res
.
Rapid
increase
in
tip
tem-
perature
under
severe
operating
conditions
causes
the
heat
shock
and
fracture
results.
Another
common
cause
of
chipped
or
broken
insulator
tips
is
carelessness
in
regapping
by
either
bending
the
center
wire
to
adjust
the
gap,
or
allowing
the
gapping
tool
to
exert
pressure
against
the
tip
of
the
center
electrode
or
insula-
tor
when
bending
the
side
electrode
to
adjust
the
gap.
Se
e
specifications
and
install
a
new
spark
plug.
F i9'
9-Prc./gniti
on
Pre-ignition.
causin
g
burned
or
blistered
in-
sulator
tip
and
badly
e
rroded
ele
c
trod
es
indi-
cates
excessive
overheating.
Clog
g
ed
shrouding,
dirty
engine
fins
and
sticky
valves
can
also
re-
sult
in
pre-ignition.
Lean
fuel-
a
Ir
mixtures
are
an
additional
cause.
S
ee
specifications
and
install
a
new
spark
plug.
Lith
o in U.S.A.
TESTING
Instructions
are
provided
for
testing
e
lec-
trical
compon
e
nts
on
and
off
the
tractor
.
The
purpose
of
the
tests
is
to
isolate
the
cause
of
trouble
in
the
ignition
system.
A
complete
diag-
nosis
guide
is
in
Group
5 of
this
Section.
Adequate
approved
electrical
test
equipment
is
required
to
accurately
test
electrical
circuits
and
intelligently
diagnose
unsatisfactory
per-
formance.
Many
servicemen
prefer
to
hav
e
their
elec-
trical
components
te
s
ted
by
prof
e
ssionals
usin
g
highly
complex
test
equipment.
Good
automoti
ve
repair
centers
provide
this
servic
e.
The
coil,
voltage
regulator,
solenoid
and
motor-
g
enerator
used
on
the
110
and
112
Lawn
and
Garden
Trac-
tors
can
be
tested
on
automotive
test
equipment.
The
following
test
procedures
are
recom-
mended
for'deal
e
rs
having
their
own
test
equip-
ment.
Equipment
needed
is
listed
on
page
10-17.
IMP
O
RTANT:
Be
cause
there
are
many
man-
uf
acluyeys
of
tes
t
equipment,
each u;ith
tl
le
i Y own
specific
opeYating
instructions
,
it
is
important
to
follow
the
manufactur
e
rs
recommendations
if
the
procedures
in
this
test
section
shoul
d
con-
tradict
t
hose
of
the
manUfacturer.
TESTING
BATTERY
Fig.
10-
T
es
tin
g
Sp
eci
fic
Grav
ity