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(337)
ELECTRICAL SYSTEMS
IGNITION SYSTEM
10-61
2. Pull cables from terminal sockets in dis-
tributor cap and coil and inspect sockets for
corrosion, clean corroded sockets, using Ter-
minal Cleaner KMO-230 or a stiff wire brush.
Blow all dust out of sockets and inside of cap.
3. Replace rotor if badly
burned.
4.
Apply
several drops of oil to wick in top
of distributor cam, then install rotor and
cap.
e
. Ignition
Coil
Faulty ignition coil operation can be caused
by
moisture,
grease or dirt on the coil cap.
Wipe off
coil
with
clean cloth.
Check the
high
tension cable connection
to
make
sure it is
clean and
t
ight
and
that the
cable n
ipp le is
properly placed
over the secondary
t
er minal.
Also
make sure that cable is tight in radio
sup-
pr essor in
:
distributor cap, if suppressor is
used at this
point.
If
coil is suspected of being
faulty it should be tested before bei
ng
replaced
(par. 10-49).
Fig ure 10-71 - ln s pection
o
f Igni
tion Cabl
e
f.
Spark
Plugs
and Ignit ion
Cables
1.
Remove all spark
plugs
for
cleaning
and
adjusting.
See paragraph 10-48.
2. Wipe
ignition
cables with cloth
mois-
tened with
kerosene,
and wipe dry. Bend cables
to check for brittle, cracked, or loose
insula-
tion. See
figure
10-71. Defective
insulation
will
permit m
issing
or cross firing of
engine, there-
fore defective
cables should
be
replaced.
3. If the cab
les
are
in
good
condition,
clean any terminals that are corroded and re-
place
any terminals that are broken or dis
-
torted. Replace any broken or deteriorated
cable nipples.
g
. Ignition Timing
After cleaning, adjustment, or replacement
of contact
points,
or removal of
distributor,
the
ignition timing must be checked and adjusted.
Even if contact points or
distributor
have not
been
disturbed during
inspection, the timing
sho
uld
be checked. See paragraph 10-47.
10-45
DISTRIBUTOR
CONTACT POINT
ADJUSTMENT
Distributor contact points adjustment must
always be made after cleaning or replacement
of contact points, and should be checked at
periodic inspection because the opening de-
creases with wear of rubbing block and
cam.
The contact point opening when breaker arm
rubbing block is on highest points of distribu-
tor cam lobes must be maintained between
.0125" and .0175".
If
the point opening is less than .0125" , the
primary
current may arc across the opened
points instead of breaking sharply. This would
cause the stored energy to be drained from the
coil so that it would not produce the required
high voltage Surge in the secondary
winding.
If
the point opening is more than .0175", the con-
tact points may not remain closed long enough
at high speed to permit sufficient flow of cur-
rent through the primary winding. The coil
would not be strongly magnetized and, there-
fore, could not produce the required high volt-
age surge in the secondary winding. In either
case, the spark produced at spark plugs would
be too weak to fire the
fuel-air
charge in the
cylinders.
Before
contact
points
are
replaced
or
checked for point opening it is advisable to
check for any fluctuation under operating
con-
ditions, as described in subparagraph a below.
Contact
point
opening
may fluctuate under
operating
conditions due to eccentric
move-
ment of the breaker plate or excessive runout
of
distributor
cam. The result is usually uneven
performance of
the
engine at low speeds. This
condition
will not be corrected by replacement
or adjustment of contact points only.
The three methods in general use for check-
ing contact point opening are discussed in the
following subparagraphs, and the adjustment
procedure is
given
in subparagraph b.
(1)
Dial
Indicator
(subpar,
b)
(2) Feeler Gauge (subpar.
c)
(3) Cam
Angle
Meter (subpar.
d)
a. Checking Contact
Point
Opening Under
Operating Conditi on s
Fluctuation of contact point opening and its
ca
use
may be checked with a cam angle meter,
as follows:
1.
With cam angle meter connected in ac-
cordance with the
manufacturer's
instructions,
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