Evinrude 4906B 4HP 1969 Owner's Manual page 165

5-6 IGNITION
may be cranked manually and the engine
started.
The flywheel-type
of an armature plate, and a permanent
net built into the flywheel.
coil, condenser and
mounted on the armature plate.
As the pole pieces of the magnet pass
over the heels of the
is built up about the coil, causing a current
to flow through the primary winding.
Now, at the proper time,
points are separated
the primary circuit
circuit is broken, the flow of primary cur-
rent stops and causes the magnetic
about the coil to break down instantly.
this precise moment, an electrical
of extremely high voltage is induced in the
fine secondary windings of the coil.
high voltage is conducted to the spark plug
where it jumps the gap between the points
of the plug to ignite the compressed charge
of air-fuel mixture in the cylinder.
5-6 TROUBLESHOOTING
Always attempt
troubleshooting in an orderly manner.
shotgun approach will only result in wasted
time, incorrect diagnosis,
unneccessary parts, and frustration.
Begin the ignition system troubleshoot-
ing with the spark
through the system until the source of trou-
ble is located.
Remember, a magneto system is a self-
contained unit. Therefore,
a key switch and wire harness, remove them
from the engine and then make a test for
The engine terminals
corrosion removed to ensure
wiring harness.
magneto unit consists
mag-
The ignition
breaker points
coil, a magnetic field
the breaker
by action of a cam, and
is broken. When the
field
current
This
to proceed with the
The
replacement
plug/s and continue
if the engine has
be and
should inspected
a proper connection
I APHRAGl1
D
are
At
Schematic
on early model small
tion depicts the position
the ground contact
pressure. Spring omitted for clarity.
spark. If a good spark is obtained with these
two items
available
nected, then the trouble is in the harness or
the key switch.
at the plug with the harness
connected,
is turned to the ON position.
of
Vacuum Cutout Switch
On some smaller engine models, a cutout
vacuum switch is installed.
connected
Schematic
the diaphragm
condition results from abnormally
on the instant
any
with slow idle speed with the engine in neutral.
shown for clarity.
of a
diagram vacuum cutout
horsepower
engine.
of
the diaphragm in relGtion
at
when operating
disconnected, but no spark is
at the plug when they are con-
If a test is made for spark
check to be sure the key switch
This switch is
to one of the cylinders
CLOSED CONTACT
diagram oj' the cutout
making contact with the ground.
high manifold suction
of rapidly throttling down from
TO MAGNETO
switch used
This illustra-
to
normal manifold
and switch
in the
TO MAGNETO
switch to depict
This
to
high
Spring not