1953 JEEP DJ engine

H

ELECTRICAL
SYSTEM

ffKHs)

3—<§)

FIG.
H-7—WIRING
DIAGRAM—V6
ENGINE
CURRENT
MODEL
1—
Left
Headlamp
2—Left Parking and Signal Lamp
3— Right Parking and Signal Lamp
4—Right Headlamp 5—
Marker
Lamp — Amber
6— Alternator 7— Voltage Regulator
8— Starting Motor
9— Battery Ground Cable
10— 12 Volt Battery
11—
Flasher
(Directional Signal)
12— Instrument Cluster
A—Hi-Beam
Indicator
B—Auxiliary

C—Instrument
Lights

D—Oil
Pressure Indicator
E—Charging
Indicator

F—Temperature
Indicator

G—Fuel
Gauge Indicator
H—Instrument Voltage Regulator
13— Ignition and Starter Switch
14—
Horn
Button
15— Directional Signal Switch
16— 4-Way Flasher Switch 17—
Flasher
(4-Way)
18— Windshield Wiper Motor Switch
19—
Main
Light Switch
20—
Fuel
Gauge
Tank
Unit
21—
Back-Up
Light Switch
22—
Marker
Lamp — Red
23— Right
Tail
and
Stop
Light 24— Right Back-Up Lamp
25—
Left
Back-Up Lamp 26—
Left
Tail
and
Stop
Light
27—
Marker
Lamp — Red
28—
Stop
Light Switch
29— Foot Dimmer Switch
30— Windshield Wiper Motor Assembly
31—
Ballast
Resistor 32— Ignition
Coil

33—
Spark
Plugs and Cables 34— Temperature Sending Unit
35—
Oil
Pressure Sending Unit 36—
Horn
37— Junction Block
38—
Marker
Lamp — Amber

lions
on the terminal
posts.
Be sure
condenser
is
mounted
firmly on the distributor for a
good
ground
connection.

Should a
condenser
tester
be available the capacity for
both
F4 and Prestolite V6
condenser
should
check from .25 to .28 microfarads. In the
absence

of
tester,
check by substituting a new
condenser.

H-13. Distributor Points
a. Examine the distributor
points.
If
they
show

wear,
poor
mating, transferred metal, or pitting,

then
new
ones
should be installed. Clean the
points

with a suitable
solvent
and a stiff bristled brush.
b. Check the
alignment
of the
point
for a full,
square
contact.
If not correctly aligned, bend the
stationary
contact
bracket slightly to provide align­
ment.

c. The
contact
gap should be set at .020"
[0,508
mm.],
on the F4 and .016"
[0,406
mm.] on the
Prestolite V6. Adjustment of the gap is accom­ plished by
loosening
the lock screw and turning adjusting eccentric screw until correct gap is
secured. Be sure that the fiber block on the breaker

arm
is resting on the
highest
point
on the cam while the adjustment is
being
made. Recheck the gap
after locking the adjustment.
d. Apply a thin film of cam lubricant to the cam to
lessen
fiber block wear.
e. Using Tool C-4094, check
point
contact
spring
pressure, which should be
between
17 and 20

ounces
[0,487
a
0,567
kg.] on the F4 and 17 to 22 oz.
[0,487
a
0,624
kg.] on the Prestolite V6.

Check
with a spring scale
hooked
on the breaker

arm
at the
contact
and pull at right
angle
to the
breaker arm. Make the reading just as the
points

separate. Adjust the
point
pressure by
loosening
the stud holding the end of the
contact
arm spring
and slide the end of the spring in or out as
neces­

sary.
Retighten the stud and recheck the pressure. Too low a- pressure will
cause
engine
missing at
high
speeds.
Too high a pressure will
cause
rapid
wear of the cam, block, and
points.
180

'Jeep'
UNIVERSAL
SERIES SERVICE
MANUAL

H

12955

FIG.
H-8—PRESTOLITE
DISTRIBUTOR—DAUNTLESS V-6 ENGINE 1—
Cap
2—
Rotor

3—
Lubricating
Wick

4—
Snap
Ring
5—
Condenser

6—
Contact
Set 7—
Breaker
Plate
8—
Cam
and Stop Plate 9—
Spring
(2)
10—
Governor
Weight

11— Cam
Spacer

12—
Gear
13—
Gear
Pin
14—
Washer

15—
O-Ring
Seal
16—
Bushing

17—
Distributor
Housing 18—
Vacuum
Chamber
19—
Washer
(Nylon)
20—
—Cap
Clamp
and Rings

21—
—Primary
Lead
22—
Washer
(outer upper,

23—
Washer
(inner upper)

2".—Drive
Shaft
H-14. Governor Mechanism
The
centrifugal advance mechanism consists of

an
automatic cam actuated by two spring con­
trolled centrifugal weights. As the
speed
of the distributor shaft increases with
engine
speed, the

weights
are thrown outward against the pull of the springs.
This
advances the cam causing the contact
points
to
open
earlier and thus advancing the

spark.
The centrifugal
type
governor should be checked for free operation. Hold the governor shaft
and
turn the cam to the
left
as far as possible

and
release it. The cam should immediately return to the original position without drag. Should a distributor
test
fixture be available it is

best
to make a check through the entire advance
range, following the instructions of the fixture manufacturer.

The
vacuum control unit is mounted separately
on the
outside
of the distributor housing on the
V6
Prestolite distributor.
The
vacuum control unit consists of an enclosed
spring-loaded diaphragm linked mechanically to the distributor. The air-tight side of the diaphragm
is connected to the intake manifold side of the

carburetor.
Under part throttle operation, the in­take manifold vacuum is sufficient to actuate the
diaphragm and cause the distributor to rotate in
its mount, thus advancing the spark and increasing fuel
economy.
During acceleration or when the
engine
is pulling heavily, the vacuum is not suf­
ficient to actuate the diaphragm and the distributor
is held in the retarded position by a calibrated

return
spring which bears against the vacuum
diaphragm.

H-15.
Distributor Removal

a.
Remove high-tension wires from the distributor cap terminal towers, noting the order in which
they

are
assembled to ensure correct reassembly.
b. Remove the primary lead from the terminal

post
at the coil.
c. Unlatch the two distributor cap springs and re­
move
the cap.

d.
Note
the position of the rotor in relation to the
base.
This
should be remembered to facilitate re­ installing and timing.
e. Remove the screw holding the distributor to the

crankcase
and lift the assembly from the
engine.

H-16.
Prestolite Distributor Disassembly

Refer
to Fig. H-8 and H-9.

a.
Remove the rotor. b. Remove the condenser.
c. Remove the distributor points.
d.
Remove nylon washer attaching vacuum ad­vance arm to breaker plate, V6 only. Remove two 181

H

ELECTRICAL
SYSTEM
FIG.
H-9—DISTRIBUTOR ASSEMBLY- HURRICANE F4 ENGINE 1—
Cap
6—Advance Plate
Lock
Screw
2—
Rotor
7—Oiler and
Felt
Wick

3—
Primary
Wire
8—Drive Shaft
4—
Breaker
Plate 9—Drive Shaft
Collar
and
Thrust
Washer 5—
Governor
Weights
attaching screws; remove vacuum advance unit
from housing.
e. Remove the two clamp
hinge
to breaker plate
screws; remove breaker plate from housing.
f. Remove the shaft assembly. To do this, file off
the upset end of the pin which is placed through
the collar and shaft at the lower end of the housing

and
drive out the pin with a suitable punch. Re­
move
the collar and washer.
Pull
the shaft from
the housing.
g. Should it be necessary to remove the cam as­
sembly, first remove the
felt
wick from the upper
end. Use
long-nose
pliers to compress and remove the spring locking clip located at the
bottom
of the

drilled
center opening of the cam. Remove the cam.

H-17.
Distributor Inspection

If
the shaft and bearings are worn sufficiently
to allow .005" or more
looseness
of the shaft,
they
must be replaced. Before installing new bearings,
soak them in medium grade
engine
oil and allow
them to
drain.
Wipe all oil from the upper part of
the housing.

Important:
After new bearing installation,
drill
a

y%"
[3,2 mm.] lubrication
hole
through the upper bearing
before
installing the drive shaft. Refer
to Fig. H-8 item 16.

At
assembly, apply a film of grease to the upper
drive
shaft washer and put a small amount of
grease in the bearing bore just
above
the bearings.

Lubricate
the governor mechanism sparingly with
medium grade
engine
oil in the oiler mounted on
the side of the housing and 5 drops on the
left

located in the center opening of the cam directly

below
the rotor. Place a very light smear of grease
on the cam and 1 drop of oil on the breaker arm pivot.
Before installing the distributor, check the friction

spring
mounted on the lower end of the drive shaft

and
replace it if worn or damaged. Inspect rod end of vacuum advance mechanism
for
excessive
wear. Push rod
into
unit as far as
possible, hold finger tightly over nipple, then release rod. After about 15 seconds, remove finger
from nipple, and
notice
if air is drawn
into
unit.
If
not, diaphragm is leaking and unit must be
replaced.

H-18.
Installation and Ignition
Timing

If
the
engine
crankshaft has
been
rotated, with the
distributor off, it
will
be necessary to place No. 1
piston in firing position to correctly install the distributor. Refer to
Pars.
C-10 and
C-ll. Oil
the distributor housing where it bears in the

cylinder
block and install the distributor on the
cylinder
block. Mount the rotor on distributor shaft

and
turn
the shaft until the rotor
points
towards No. 1
spark
terminal tower position (when cap is installed) with the contact
points
just breaking. Move the rotor back and forth slightly until the

driving
lug on the end of the shaft enters the
slot

cut in the oil pump gear and slide the distributor
assembly down
into
place. Rotate the distributor
body
until the contact
points
are just breaking.
Install
the hold down screw.

H-19.
Ignition
Coil
— F4 Engine

The
sealed coil
does
not require any special service
other than keeping the terminals and wire con­ nection clean and tight.

The
positive (+) terminal of the coil is connected
to the ignition switch and is also connected directly
to the starter solenoid to by-pass the resistance

during
cranking of
engine.

The
negative
(—) terminal is connected to the
distributor. The secondary (High tension) terminal
is connected by a short cable to the center terminal

in
the distributor cap.

Note:
Always make certain the coil wires are con­
nected to the proper coil terminals to ensure cor­
rect coil polarity.

H-20. DELCO DISTRIBUTOR
—
DAUNTLESS
V-6
ENGINE
The
distributor (Fig. H-10) is mounted at the
left

front of the
engine
on the timing chain cover. It
is driven by a
spiral
gear on the camshaft. The

spark
advance is fully automatic, being controlled 182

'Jeep*
UNIVERSAL
SERIES SERVICE
MANUAL

H
|
13399

FIG.
H-10—DELCO
DISTRIBUTOR—
DAUNTLESS
V-6
ENGINE

1—
Rotor
8—Vacuum
Unit

2—
Window
9—Breaker Cam
3—
All
Weather Cap
10—Drive
Gear

4—
Cap
Latch
11—Primary Lead 5—
Rotor
Mounting
Screw 12—Contact Set
6—
Lock
Washer 13—Condenser

7—
Advance
Mechanism
by
built-in
centrifugal weights, and by a vacuum

advance
system. Contact point opening is adjusted
through
a window in the distributor cap
while
the engine is
idling.
Some
parts
of the distributor may be checked or replaced
with
the distributor mount­
ed on the engine, but it is
best
to remove it periodi­
cally
for a thorough check. Information on
parts

which
can be serviced without removal is given
below.

Note:
Prestolite and Delco distributors are inter­

changeable
on V-6 engine equipped vehicles.

H-21.
Distributor Cap
The distributor cap should be inspected for cracks,
carbon runners and evidence of arcing. If any of

these
conditions exist, the cap should be replaced. Clean any corroded high tension terminals.

H-22.
Rotor
Inspect the rotor for cracks or evidence of
exces­

sive burning at the end of the metal strip.
After
a distributor rotor has had normal use, the
end of the rotor
will
become
burned. If burning is
found
on top of the rotor it indicates the rotor is too short and
needs
replacing. Usually when this
condition
is found the distributor cap
segment
will

be burned on the horizontal face and the cap
will

also
need
replacing.
H-23.
Condenser
The
condenser
prolongs the
life
of the distributor
points by preventing arcing at the contacts. It
also

provides a hotter spark by creating a
reverse
surge

of
current
which
rapidly
breaks
down the magnetic
field
of the
coil
by demagnetizing the core. Should
the
ccnaenser
be leaky a weak spark
will
result. Check the
condenser
lead for broken wires or

frayed
insulation.
Clean and tighten the connections
on
the terminal
posts.
Be
sure
the
condenser
is mounted
firmly
on the distributor for a good ground
connection.

Should
a
condenser
tester
be available the capacity
should check
from
.18 to .23 microfarads. In the

absence
of a
tester
check by substituting new con­
denser.

H-24. Distributor Points

a-
Examine distributor points. Using
Tool
C-4094, check point contact spring
pressure,
should be 19 to 23 oz. [0,538 a 0,652 kg.]. Install new points

if
they are
worn,
pitted,
mate
poorly, or show
signs

of
metal transfer. Should premature
ignition
point

failure
occur
because
of dust entering the
distri­

butor cap and causing
excessive
wear to the
ignition

point
fiber block, perform the
following
correc­
tions after installing new distributor points.
FIG. H-l
1—SEALING
DISTRIBUTOR
CAP

1—Caulking
Compound
183

H

ELECTRICAL
SYSTEM

14237

FIG.
H-l2—DRILLING DISTRIBUTOR
CAP 1—%'
Vent
Hole
Location
Seal
the distributor cap access window and the

area
beneath the distributor cap with caulking
compound as shown in
Fig. H-ll.
At approximately
180°
from the distributor cap access window,
drill
a
[2,38 mm.] vent
hole
[31,75
mm.]
from the
bottom
of the distributor cap as shown

in
Fig. H-l2. b. To adjust breaker point cam dwell, refer to

Par.
C-10.

H-25.
Centrifugal Advance

Refer
to Fig. H-13.
Inspect for
excessive
wear
between
centrifugal

weights
and advance cam, or pivot pins.
Turn

weight
base plate in a clockwise direction until

weights
are fully extended, then release and allow springs to return to retard position. Repeat several times. Springs should return
weights
to
stop
with­out sticking and there should be no
excess
free

movement
in the retard position.

H-26.
Distributor Removal

a.
Disconnect the distributor primary wire from
coil
and disconnect
hose
from vacuum advance
mechanism of distributor. Insert a screwdriver in upper
slotted
end of two distributor cap retainers.

Press
downward, and turn 90
degrees
counterclock­
wise to release. Remove cap from distributor hous­ ing.
b. Make an index
mark
on distributor housing

(Fig.
H-14) in line with center of rotor. Carefully

note
the direction the vacuum unit
points
in
rela­

tion to
engine
so that the distributor can be in­
stalled in the same position after it is serviced.

Caution:
If
engine
is turned over while distributor is removed,
complete
ignition timing procedure
must be followed upon distributor installation.
c. Remove attaching cap screw and distributor
clamp from timing chain cover.
Lift
distributor up­

ward
and remove it from timing chain cover.

H-27.
Distributor Disassembly (Delco)

Refer
to Fig. H-l5.

a.
Remove rotor, breaker point assembly, and capacitor from distributor.
FIG.
H-13—CENTRIFUGAL ADVANCE
MECHANISM (DELCO)
A—No
Advance
1—
Advance
Weights

2—
Advance
Cam
B—Full
Advance

3—Full
Advance
FIG.
H-14—DELCO DISTRIBUTOR

ROTOR
POSITION
1
—Rotor
Tip
Lined
Up
With
Notch

184

'Jeep*
UNIVERSAL
SERIES SERVICE
MANUAL

H
FIG.
H-l 5 -DELCO
DISTRIBUTOR—
DAUNTLESS V-6 ENGINE

1—
Cap Assembly
2— Rotor
3— Governor Weight
4— Rotor
Mounting
Screw 5—
Lock
Washer
6—
Weight
Spring (Governor) 7— Shaft
8— Cam Assembly
9—
Gear
Pin
10—
Drive
Gear

11—
Spacer
Washer
12—
Housing

13—
Vacuum
Control
14—
Lock
Washer

15—
Control
Mounting
Screw
16—
Primary
Lead
17— Lead Gromet
18— Washer

19—
Breaker
Plate

20—
Condenser

21—
Retaining
Spring
22—
Ground
Lead
23—
Condenser
Clsmp
24— Contact Set
25— Clamp Screw

26—
Lock
Washer
27— Contact Screw

28—
Insulator 29—
Spring
Clip

30—
Screw 13400

b.
Remove and discard
O-ring
seal from distributor
housing.
c. Remove two attaching screws; remove vacuum
advance from housing.

d.
Drive pin from driven gear and shaft, using a
y%"
[3,2 mm.] straight punch. See Fig. H-l6.

Caution:
Be careful not to bend distributor shaft
or damage gear when driving pin out.

e.
Remove gear and thrust washer from shaft; pull the shaft, breaker cam, and centrifugal advance
mechanism from the housing.
f. Remove two springs and centrifugal advance
weights
from the integral
weight
base plate and

breaker
cam. Remove plate from end of shaft.
g. Remove retainer breaker plate, and
felt
washer from upper bushing.

Note:
Lubricant
reservoir contains sufficient
lubri­

cant for the life of the distributor. Do not
move
plastic reservoir cover from housing. Do not de-
grease bore of housing.
h. Remove distributor primary lead and grommet
from housing.

Caution:
Do not attempt to replace the shaft
bushings in the housing; the housing and bushings

are
serviced only as an assembly.
FIG.
H-l6—DISTRIBUTOR GEAR AND
SHAFT PIN REMOVAL (DELCO) 1— H' Punch

2—Spring
Pin
H-28.
Distributor Parts
Cleaning
and

Inspection

a.
Wash the distributor housing, shaft, gear, break­

er
plate, and
weight
base and cam in suitable clean­ ing solvent. Hold housing in horizontal position to
avoid
getting
cleaning solvent
into
the lubricant
reservoir.
Dry parts thoroughly.

b.
Wipe distributor cap with a clean cloth. Inspect
it for chips,
cracks,
and carbonized paths which
would allow
high-voltage
leakage. Such
defects
re­
quire
replacement of cap.
Clean
loose
corrosion
from surfaces of terminal
segments
inside the cap. Do not use emery cloth or sandpaper. If
segments

are
deeply
grooved, the cap should be replaced.

Pull
cables from terminal
sockets
and inspect
sockets
for corrosion.
Clean
sockets, using a stiff

wire
brush to
loosen
corrosion.

c.
Inspect rotor for wear and damage. If rotor is
cracked,
spring contact is badly worn, or rotor tip is badly burned, rotor must be replaced. 185

ELECTRICALJ
SYSTEM

d.
Inspect for
excessive
wear
between
centrifugal

weights
and advance cam and pivot pins.
Turn
weight
base plate in a clockwise direction until
weights
are fully extended. Release and allow
springs to return
weights
to
retard
position. Repeat several times. Springs should return
weights
to
stop
without sticking and there should be no
excessive
free
movement
in the
retard
position. Inspect
springs for distortion and fatigue.
e. Inspect cam
lobes
for scoring or
excessive
wear.
Check
weight
base plate for binding or
excessive

looseness
on distributor shaft.

f.
Check
breaker plate for
excessive
looseness
on
outside
diameter of upper distributor shaft bushing.
Check
breaker plate ground lead for poor
spot
we
Id

at plate end and for
loose
or frayed terminal con­
nections.
g.
Check
for
excessive
wear
between
distributor
shaft and bushings in housing. Inspect shaft for distortion. Inspect gear for scoring of
teeth
or

excessive
wear.

h.
Inspect rod end of vacuum advance mechanism
for
excessive
wear. Push rod
into
unit as far as
possible, hold finger tightly over nipple, then re­
lease
rod. After about 15 seconds, remove finger
from nipple, and
notice
if air is drawn
into
unit.
If
not, diaphragm is leaking and unit must be
replaced.

H-29.
Distributor Reassembly

Refer
to Fig. H-l5.

a.
Install
distributor
primary
lead and rubber grommet in distributor housing. Mount vacuum
advance unit on housing with two
slotted
attaching
screws; insert ground lead terminal of breaker plate under outer mounting screw.
b.
Install
felt
washer over upper shaft bushing of
distributor housing and apply a few drops of light

oil.
Secure breaker plate to upper bushing with re­ tainer. See Fig. H-17.
12767

FIG.
H-17—INSTALLING
BREAKER
PLATE
ON
DISTRIBUTOR
HOUSING
(DELCO)

1—
Breaker
Plate
2—
Retainer

3—
Retainer
Groove
4—
Lubricant
Reservoir c.
Install
distributor cam and
weight
base plate
on distributor shaft.

d.
Insert distributor shaft
into
distributor housing.
Install
centrifugal advance
weights
and springs on

cam
and
weight
base plate. e. Fasten driven gear to shaft with pin. Be care­
ful
not to damage gear.

f.
Secure condenser and bracket to breaker plate
with
slotted
screw.
g.
Install
breaker point assembly over
boss
on
breaker
plate; secure with two
slotted
screws and
lock washers. Apply one drop of light oil to breaker

arm
pivot. Connect condenser and coil
primary

leads to breaker point assembly.

h.
Apply a small amount of high temperature cam

and
ball
bearing lubricant to a clean cloth; hold cloth against distributor cam while turning
distri­
butor shaft.

Caution:
Do not apply
excessive
grease. Petro­
leum jelly is not suitable as a distributor cam
lubri­
cant.

i.
Make preliminary adjustment of breaker point
gap, as described in Par. C-10.

].
Secure rotor to centrifugal timing advance mech­
anism with two screws, lock washers, and flat
washers.

Note:
The square and round
lugs
on the rotor must
be positioned in the corresponding
holes
in the

weight
base plate.
k. If a reliable distributor tester is available, check
the distributor to make certain that the centrifugal

and
vacuum advance mechanisms are operating
according to specifications.

Note:
Mount distributor in tester with all end play
of the distributor shaft in upward position; this

will
eliminate any possible drag
between
the centri­ fugal advance cam and
weight
base plate.

I.
Install
new
O-ring
seal on distributor housing.

H-30.
Distributor
Installation
and
Timing

a.
Insert distributor shaft
into
timing gear cover
of
engine
so that rotor is pointing to
mark
made on distributor base (Fig. H-14), with vacuum advance
unit pointing in exact, original direction (Fig.

H-18).

b.
Install
distributor clamp and
bolt
with lock
washer, leaving
bolt
just
loose
enough
to permit
movement
of the distributor with heavy hand
pressure.

C.
Connect
primary
wire to distributor side of coil.
Install
distributor cap on distributor housing. Press

screwdriver
into
upper
slotted
ends
of two cap
retainers.
Turn
retainers clockwise to secure cap to distributor.

d.
If
spark
cables were disconnected from
distri­

butor cap, connect them. Wires must be pushed

all
the way down
into
the distributor cap terminals
and
onto
the
spark
plugs. Nipples must be pushed
firmly
over the terminals;
boots
must be pushed

firmly
over the
spark
plugs. 186

'Jeep'
UNIVERSAL
SERIES SERVICE
MANUAL

H

12746

FIG.
H-l8—VACUUM
ADVANCE
MECHANISM
(DELCO)

A—Full
Advance

B—No
Advance
1—Vacuum
Pull
Rod
e.
To adjust breaker point cam dwell and set tim­
ing of engine, refer to
Pars.
C-10 and
C-ll.
H-31. Coil
— V-6 Engine

The
sealed coil
does
not require any special service
other than keeping the terminals and wire connec­
tions clean and tight.

The
positive (+) terminal of the coil is connected
to the ignition switch through the ballast resistor,
and
is also connected directly to the starter
sole­

noid to by-pass the resistance during cranking of
engine.
The
negative (—) terminal is connected to the

distributor.
The secondary (high tension) terminal
is connected by a short cable to the center terminal
in
the distributor cap.

Always
make certain the coil wires are connected to the proper coil terminals to ensure correct
coil
polarity.

Note:
The ignition coil and ballast resistor must
be of the same manufacturer. Ballast resistors
and
ignition coils of one manufacturer are inter­changeable with both units of the other. H-32.
Ballast
Resistor

•
V-6 Engine.

An
ignition ballast resistor is in series with the
primary
winding of the coil. The ballast resistor
helps regulate the flow of
primary
current through­
out the speed range. At low
speeds
when the con­
tacts remain closed longer, the ballast heats and
increases in resistance, thereby limiting the flow of

primary
current. At higher
speeds
when the con­
tacts remain closed for shorter periods of time, the ballast
cools
and thereby decreases in resistance
to allow more
primary
current and reduce the
fall

off
in
available voltage.
During
starting, the resistor compensates for the lowered battery
voltage
re­
sulting from the starter load and permits an in­ crease in
primary
current, resulting in a higher
secondary
voltage
for starting.
The
only
test
required of the ignition ballast re­
sistor is a continuity check. Characteristics of the ballast produce wide variations in resistance with
changes in ballast temperature. Therefore, check­ ing
voltage
drop across the ballast would be mis­
leading.

Caution:
Never make a connection that connects
the ballast across the battery as this
will
burn
the ballast resistor winding.

H-33.
Spark
Plugs

Clean
and gap
spark
plugs as described in
Par.
C-4.
Inspect them for excessive burning and erosion of
electrodes, blistering of porcelain at the firing tip,

black
deposits, or fouling. These conditions indicate
that the plugs have not been operating at the cor­

rect
temperature.

Note:
Prolonged idling just before removing and
checking the plugs should be avoided as it may
produce false indications.

Spark
plug operating temperatures may have been
too hot, too cold, or normal as described.

a.
At too hot a temperature, the tip of the insulator
will
show
dark
spots
and blisters after fairly short service. As high-temperature operation is con­
tinued, the whole insulator
nose
will
discolor, show­
ing fused and blistered
deposits
near the electrode
as well as considerable erosion and burning of the
electrodes. After extreme service, the porcelain it­ self may be fused, cracked, and blistered at the tip.

The
electrodes
will
show extreme erosion and
burn­

ing and possibly even surface cracking.

Note:
If such cracking appears on certain plugs
after fairly short service, it may be caused by water
leaks in the associated cylinders.
b. At too cold a temperature plug operation, in
the early
stages,
will
result in a
dull
black
sooting

of the plug.
This
condition frequently is found in new vehicles during the break-in period and is no
indication of trouble in this case. As the condition progresses, black
deposits
of oil and carbon build
up on the base of the shell and on the insulator

until,
in extreme cases, the space
between
insulator

and
shell may be almost completely filled. Excessive
electrode erosion
will
seldom be found in cases of cold plug operation. These indications can be pro­
duced by the use of an excessively
rich
air-fuel mixture and the carburetor should be checked if
this condition is suspected. Fouling
will
also be
caused by leaking rings or intake valve
guides
that
permit excessive oil to reach the combustion
chambers.
The use of a hotter plug
will
help
burn

away
some
of this fouling but the mechanical con­ dition of the
engine
should be corrected.
c. In normal temperature operation the plug
will
accumulate grayish-tan to reddish-brown
deposits

with
fairly uniform discoloration of the insulator
nose
and slight, localized electrode erosion. If the
insulator shows any blotches, blisters,
irregular
dis­
coloration, etc., look for hot-plug symptoms. Too
hot or too cold plug operation may be caused by
the use of plugs of other than the specified heat

rating
but if the plugs are as specified a hotter or 187