5.
MM
-1 Clip
The
MM-1
clip determines
the
relative
amount
of
energy
present in the spark plug
wires
.
En
-
gines
in
various stages of
wear
will
indicate a
different
energy reading
than
new
engines. As
the
engine
compression goes
down,
the energy
necessary to fire the plugs goes
down
also.
Readings
lower
than
standard indicate
low
coil
output
(caused
by
a
fault
anywhere
in the igni-
tion
system, faulty spark plug or
ignition
wire,
or
low
compression). Readings
higher
than
standard indicate hi
gher
coil
output
or larger
than
standard spark plug gap.
GE
NERAL TEST INSTRUCTIONS
Engine Accessory Circuits
Before
beginning
test procedures, check all
primary
and
secondary
i
gnition
wiring,
key
switches,
and
engine
stop
switches
to
eliminate
them
as possible
causes
of
ignition
failure
.
Starting
With
Magneto Ignition
Removal
of
the
spark plugs
will
allow
the
engine
to
turn
over faster, raising
the
level
of
output
from
the
ignition
system. Vigorous cranking raises
the
output
over
that
of cranking
without
compression.
If
output
results
are marginal.
output
can
be
mea-
sured
with
and
without
compression. Values listed
in the
test
procedures are taken against com-
pression.
Always
crank vigorously
as
in actual
starting.
Analysis
of
Test Results
Indicator
Lamp
Lights at Specified Setting:
After
every test
that
lights the indicator lamp, re-
set
the
indicator
circuit
by depressing
the
Reset
button
. The Indicator lamp
will
light
at all points
downscale
from
the
highest
indication.
Test
results
should repeat
within
five points of
the
specified setting. If readings do
not
repeat,
output
of
the
ignition
system is
erratic
.
Indicator Lamp Does Not Light Unless Dial
Is
Turned
Downscale
From Specified Setting:
3-10
ELECTRICAL
TROUBLESHOOTING
This indicates
that
the
output
is
less
than
that
designed to operate
the
engine in a satisfactory
manner. The engine may run at a
lower
setting,
but
be
subject to hard starting and/
or
misfir
i
ng
.
Be
certain that correct engine
cranking
conditions
were met.
Indicator
La
mp Does Not Light:
Output
of the system is too
low
to
operate the
tester indicator circuit.
Multiple
or
Intermittent
Ignition Problems
In dealing wi
th
interm
ittent
i
gnitio
n problems there
is no
" easy"
way
. Problems
that
occur
only during
hot engine operation
will
have to be tested on a
hot engine.
In some cases of
temperature
and/ or
vibration
failure, only parts
replacement
can solve
the problem
as
most of these
failures
return to
normal at engine shut off.
Low test readings indicate
ideal
conditions
for en-
gine misfire and hard starting.
There
is
always
the
possibility of more
than
one
component of the
ignition
system fa iling. Careful
repeat of the test procedures and
troub
leshooting
of the accessory circuits
will
uncover
any addi-
tional problems.
IWARNINGI
Magneto
and
COl
igniter
output
voltages
are
high
enough
to
cause
an
uncomfortable
shock.
Always
see
that
clip
lead insulators cover the clips
so
they
do
not
contact the operator
or
vehicle frame.
Never
perform
tests
on
the
COl
igniter
without
the
ignition
coil
or
the
tester
connected
to the
output
connections
. This
will
prevent
internal
damage
to
the
COl
igniter
.
Never
connect
the
tester
directly
to the
coil
secondary
output
(spark plug).
Always
use
the
MM
- l clip
when
testing
the
ignition
coil
output.
}
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