1953 JEEP CJ check engine light

'Jeep'
UNIVERSAL
SERIES SERVICE
MANUAL
Dl
A 8

j
13415

FIG.
Dl-13—USING
PLASTIGAGE
TO
MEASURE
BEARING CLEARANCE

1— Plastigage
A—Start

2—
Scale
B—Flattened

install
cap with shell and tighten
bolts
80 to 110 lb-ft. [11,1 a 15,2 kg-m.] torque.

Caution:
Do not turn crankshaft with Plastigage

in
bearing.

b.
Remove bearing cap with bearing half. The
flattened Plastigage
will
adhere either to the bear­ ing half or the
journal.
Do not remove it.
c. Using the scale printed on the Plastigage en­

velope,
measure Plastigage width at its widest
point. The number within the graduation which
most
closely corresponds to the width of Plasti­
gage
indicates the bearing clearance in thousandths
of an inch.

DI-43.
Main Bearing
Fitting,
Feeler or
Shim
Stock

A
small strip of feeler or shim stock can be used
to check main bearing clearance. The method is
simple, but care must be taken to avoid damage
to the bearing surface from excessive pressure against the strip.

a.
Cut a rectangular piece of feeler or shim stock, .001"
[.0254
mm.] thick,
i/2"
[12,70
mm.] wide, and
Vs"
[3,175 mm.] shorter than the bearing width.
Position the bearing cap to the crankshaft journal
and
cylinder block, and install two cap
bolts
loosely.

b.
Tighten alternate cap bolts, a little at a time,

until
both have
been
tightened to 35 to 45 lb-ft. [4,8 a 6,2 kg-m.] torque.
c.
Turn
the crankshaft by hand, no more than one

inch
[2,5 cm.] in either direction.

Caution:
If the crankshaft is turned too far, it
will

embed the strip in the bearing surface.
This
will
damage the bearing and also cause a false indica­tion of bearing clearance.

If
bearing clearance is correct, the strip should cause a light to heavy drag, or resistance to rotation.
If
there is little or no drag, clearance is too great;

if
the crankshaft cannot be turned, clearance is
insufficient. In either case, a different main bear­ ing must be
selected
to obtain proper clearance.

d.
Repeat
steps
a, b, and c, as necessary, to
select

proper main bearing size. After a bearing has
been

selected, remove the
test
strip from bearing on
crankshaft
journal surface; wipe both surfaces care­

fully,
and apply clean
engine
oil to both surfaces. Position the bearing cap to the crankshaft journal

and
cylinder block, and install two cap
bolts
loosely.

Tighten
alternate cap bolts, a little at a time, to

final
specified torque of 80 to 110 lb-ft. [11,1 a 15,2 kg-m.]. The crankshaft should now rotate
freely.

Dl-44.
Piston
and
Connecting
Rod
Disassembly

a.
Remove two compression rings with a piston
ring
expander. To remove oil ring, remove the two

rails
and spacer-expander, which are separate
pieces

in
each piston third
groove.

b.
From
Tool Set W-338 use support base J-6047-1
with collar J-6047-5 and driver J-6047-4 with an
arbor
press to press piston pin from piston and con­
necting rod. Mount support base and collar in press. Set driver in position and press out pin. Refer to

Fig.
Dl-14.
FIG.
Dl-14—PISTON
PIN
REMOVAL

1—
Arbor
Press

2—
Driver

3—
Piston
and Rod Assembly
4—
Collar
•
5—Support Base Dl-45.
Piston
and
Connecting
Rod
Cleaning
and Inspection

a.
Clean
carbon from piston surfaces and under­
side of piston heads, and remove all pistons rings.
Clean
carbon from ring
grooves
with a suitable tool.
Remove any gum or varnish from piston skirts with a suitable solvent.

b.
Carefully examine pistons for rough or scored
bearing surfaces, cracks in
skirt
or head, cracked

or
broken ring lands, chipping and uneven wear 87

Pi

DAUNTLESS
¥-6
ENGINE
which
would cause rings to seat improperly or have
excessive clearance in
ring
grooves. Damaged or
faulty
pistons should be replaced,
c.
Inspect bearing surfaces of piston pins and check

for
wear by measuring worn and unworn surfaces

with
a micrometer. Rough or worn pins should be
replaced.
Test fit the piston pins in piston
bosses.
Occasionally,
a pin
will
be tight due to gum or

varnish
deposits.
This
may be corrected by remov­

ing
the deposit with a suitable solvent. If piston
bosses
are worn out-of-round or oversize, the piston

and
pin assembly must be replaced. Oversize pins
are
not
practical,
since the pin must be a press fit
in
the connecting rod bore. Piston pins must fit the
piston with an easy finger push at
70°F.
[21°C.].

They
should have .0004" to .0007"
[0,0178
a
0,0102
mm.] clearance.

Dl-46.
Piston Fitting

If
cylinder bores are rebored or heavily honed,
new and possibly oversize diameter pistons must be
installed.
A new piston must be fitted to its cylinder

bore.
A satisfactory method of fitting pistons is as
follows.

a.
Expand
a
telescope
gauge
to fit the cylinder bore at right angles to the piston pin and
between
1
Vi"
to 2" [3,7 a 5,1 cm.] from the top.

b.
Measure diameter of the piston to be fitted, as
shown in
Fig.
Dl-15. The piston must be measured

at
right angles to the piston pin, W [6,3 mm.] below the oil
ring
groove. The piston must be be-
FIG.
Dl-15—MEASURING
PISTON

1—90°
tween .001" and .0015" [0,025 a
0,038
mm.]

smaller
than the cylinder bore.

Note:
Both cylinder block and piston must be at

very
nearly the same temperature when measure­
ments are made or
errors
due to expansion
will
occur.
A difference of 10°F.
[5,6°C]
between
parts
is sufficient to produce a variation of .0009"
[0,0023
mm.].

The
pistons are cam-ground, which means that the
diameter at a right angle to the piston pin is
greater
than the diameter
parallel
to the piston

pin.
When a piston is checked for size, it must be
measured
with a micrometer applied to the
skirt

along a line
perpendicular
to axis of the piston pin.

Dl-47.
Piston Ring Fitting

When
new piston rings are to be installed without

reboring
cylinders,
the glazed cylinder walls should
be slightly dulled. However, cylinder bore diameter
should
not increase more than necessary.
Cylinder

walls
should be honed with the finest grade of
stone
to remove any glaze.
New compression rings must be checked for clear­ ance in piston
grooves
and for gap in cylinder bores;
however, the flexible oil rings are not checked for gap. The cylinder bores and piston
grooves
must
be clean, dry, and free of carbon and
burrs.

With
rings installed on piston, check clearance in
grooves
by inserting feeler
gauge
between
each
ring

and
its lower
land.
Any
ring
groove
wear
will
form

a
step
at inner portion of the lower
land.
If the
piston
grooves
have worn enough that relatively

high
steps
exist on the lower lands, the piston
should
be replaced because the
steps
will
interfere

with
proper operation of new rings and the
ring
clearances
will
be excessive. Piston rings are not

furnished
in oversize widths to compensate for
ring
groove
wear.

When
fitting new rings to new pistons, the side

clearance
of the compression rings should be .002" to .0035"
[0,051
a
0,089
mm.] for number one (1)

ring,
.003" to .005" [0,076 a 0,127 mm.] for number
two (2)
ring,
and side clearance of the oil
ring
should
be .0015" to .0085" [0,038 a
0,220
mm.].

To
check the end gap of a compression
ring,
place

it
in the cylinder in which it
will
be used, square

it
in the bore by tapping with the lower end of
a
piston, then measure the gap with a feeler
gauge.

A
compression
ring
should not have
less
than .015"
[0,381
mm.] gap when placed in cylinder

bore.
If gap is
less
than specified value, file the
end of the
ring
carefully with a fine file to obtain

proper
gap.

Dl-48.
Piston and Connecting Rod Assembly

Note:
A connecting rod can spring out of alignment

in
shipping or handling. Always check a new con­
necting rod for misalignment before installing pis­
ton and pin.

a.
If a new connecting rod is to be installed, check
its alignment with an accurate rod alignment fix­

ture.

b.
If the piston and connecting rod assembly is
to be installed in the left cylinder bank, it must be assembled as shown in
Fig.
Dl-16. If the piston and
connecting rod assembly is to be installed in the
right
cylinder bank, it must be assembled as shown
in
Fig. Dl-17.
Note
that
these
two assemblies are

mirror-images
of each other.

c.
Lubricate
piston pin to avoid damage when

pressing
through the connecting rod.

d.
To install piston pin in piston and connecting

rod,
use
Tool
Set W-338.
Install
collar J-6047-5,
spring
J-6047-3, and pilot J-6047-20 into the base

support
J-6047-1 and place in
arbor
press. Using

driver
J-6047-4 press piston pin into piston and 88

DAUNTLESS
V-6
ENGINE

Note:
The rib on
edge
of cap and the conical
boss

on web of connecting rod must be toward
rear
of
engine
in all connecting rod assemblies of left
cyl­

inder
bank and toward front of
engine
in all con­necting rod assemblies of right cylinder bank.

Dl-50.
Oil
Pump Intake
and
Screen Cleaning

a.
Pry screen from housing and examine for clog­
ging due to deposit of sludge or other foreign

material.

b.
Clean
the screen and housing thoroughly in sol­
vent; dry with compressed air.

c.
Install
screen in housing.

Dl-51.
Oil Pan Cleaning and Inspection

Inspect
the oil pan for corrosion, dents, leaks, and
other damage. Inspect its mounting flange carefully
for damage or distortion to be certain that it
will
give
a
good
seal.

Dl-52.
Flywheel Cleaning
and
Inspection

Clean
the flywheel with suitable cleaning solvent;

dry
with compressed air. Inspect clutch face for

burned
or scuffed condition and for rivet grooves.
Inspection
for run out or improper mounting is de­

scribed
in installation procedure.
Inspect
teeth
of the flywheel
ring
gear for
burrs,

nicks,
and minor distortion. If necessary and pos­
sible, use a small emery wheel to remove
burrs
and
reshape teeth. If gear
teeth
are broken,
cracked,

seriously
burred
or deformed, the
ring
gear must be replaced.

Dl-53.
Ring Gear Replacement

a.
Drill
a
hole
between
two
ring
gear teeth; then

split
the gear with a cold chisel. Be careful not to
damage
ring
gear shoulder or seat surfaces of fly­
wheel.

b.
Polish several
spots
on the new
ring
gear to be

installed.
With
a hot plate or slowly moving torch,
heat the new
ring
gear until polished
spots
become

blue, about
600°F.
[312°C.].

Caution:
Do not heat the
ring
gear to a temperature
greater than
800°F.
[424°C.].
Excessive heat
will

destroy heat treatment given to
ring
gear during
manufacture.

c.
Quickly
install
ring
gear on flywheel. Chamfered

edge
of
ring
gear must be toward
ring
gear shoulder
of flywheel. Be certain that
ring
gear is seated prop­

erly.
Allow
ring
gear to cool slowly, so that it
will

be held tightly in place.

Dl-54.
Flywheel Housing Cleaning and Inspection

Both
flywheel and clutch are enclosed by a fly­
wheel housing. Its front surface is bolted to the
engine
cylinder block, and its
rear
surface acts as

front
support to the transmission.
Clean
the fly­ wheel housing with a suitable cleaning solvent; dry
with
compressed air. Inspect front and
rear
surfaces
for distortion and improper alignment with each
other;
these
planes must be
parallel
to assure
proper
alignment
between
engine
and transmission.
Dl-55.
Camshaft Cleaning
and
Inspection

Clean
both camshaft and camshaft bearing surfaces

with
a suitable cleaning solvent; dry with com­
pressed air.

Note:
The steel-backed babbitt-lined camshaft
bearings are pressed into the crankcase.
From
front
to
rear,
each bearing is .030" [0,76 mm.] smaller
in
diameter than the preceding bearing.
From
front
to
rear,
each camshaft
journal
is correspondingly
smaller
in diameter.

The
camshaft bearings must be line reamed to

proper
diameter after being pressed into crankcase.
Since
this operation requires special reaming equip­
ment, the original bearings should be retained un­
less
they are severly damaged. Slightly scored cam­
shaft bearings are satisfactory if the surfaces of camshaft journals are polished, bearings are
polished to remove
burrs,
and
radial
clearance

between
camshaft and bearings is within .0015"
to .004" [0,038 a 0,102 mm.].

Dl-56.
Valve Lifter
and
Push
Rod
Cleaning and Inspection
a.
Examine the cam contact surface at lower end of each valve lifter body. If surface is excessively

worn,
galled, or otherwise damaged, discard the
valve lifter. Also examine the mating camshaft
lobe
for excessive wear or damage.

b.
Disassemble one or two valve lifters, as de­

scribed
below, and inspect them for
dirt
or
varnish.
If
they are dirty or have a varnish deposit, clean

and
inspect all twelve valve lifters. Otherwise,
service
only
those
valve lifters which do not operate

properly.

c.
To disassemble each valve lifter, depress the
push
rod seat with a push rod, and remove the
plunger retainer from the valve lifter body with

a
retainer remover. Remove push rod seat and
plunger from valve lifter body. If plunger sticks
in
valve lifter body, place body in large end of

a
plunger remover tool, with plunger downward.
While
holding lifter with thumb, rap the open end
of remover against a block of wood with just enough force to jar the plunger from body. Refer to
Figs.
Dl-20, Dl-22 and Dl-23.

d.
Drain
oil from valve lifter and remove the check
valve retainer,
ball,
valve spring, and plunger
spring.

e. Keep all parts of each valve lifter separated

during
part cleaning and inspection. The valve

lifter
body and plunger are selectively fitted to each other and must not be interchanged with parts
of other valve lifters.
f. Rinse all valve lifter parts in kerosene to remove as much oil as possible.
This
will
reduce contamina­
tion of the cleaning solvent. Immerse all parts in cleaning solvent for approximately one hour. The
time required
will
depend on varnish
deposits
and
effectiveness
of the solvent. After the varnish has
dissolved or has
softened
sufficiently to permit re­

moval
by wiping, allow parts to
drain.
Varnish
can
then be cleaned from the valve lifter body
with
a
brush.
Rinse the parts in kerosene to dissolve 90

Dl

DAUNTLESS
V-6
ENGINE

FIG.
D1-28—CLEANING
OR
ENLARGING
VALVE
GUIDE

1—Reamer
d.
Measure clearance of each valve stem in cor­
responding valve guide. For intake valves, this
clearance
should be .0012" to .0032" [0,0305 a

0,0813
mm.]. For exhaust valves, this clearance should be .0015" to .0035"
[0,0381
a
0,0889
mm.]
at top of guide and .002" to .004"
[0,051
a 0,102 mm.] at bottom of guide. If this clearance is exces­
sive, valve guides must be reamed with .004" [0,102 mm.] oversized reamer J-5830-1 and valves

replaced
by new valves with oversize stems.

Dl-63.
Cylinder
Head
and Valve
Repair
a.
If a valve stem has excessive clearance in its
guide, the guide must be reamed .004" [0,102 mm.]
oversize. Valves are available with oversize stems
to fit this valve guide diameter.

b.
Grind
valve faces or replace valves if necessary.

Valve
faces must be ground at an angle of 45 degrees. If a valve head must be ground to a
knife
edge
to obtain a true face, the valve should
be replaced.

c.
If necessary, grind valve seats at an angle of 45 degrees.
Grinding
a valve seat decreases valve
spring
pressure and increases the width of the seat.

The
nominal width of the valve seat is
[
1,59
mm.].
If a valve seat is wider than %" [1,98 mm.]
after grinding, it should be narrowed to specified

width
by the use of 20-degree and 70-degree stones.
Improper
operation of a hydraulic valve lifter may

result
if valve and seat are refinished to the extent
that the valve stem is raised more than .050" [1,27 mm.] above normal height. In this case, it
is necessary to grind off the end of the valve stetti or replace parts.

Note:
The normal height of the valve stem above
the valve spring seat surface of the head is
1.925"
[4,889 cm.].

d.
Lightly
lap the valves into seats with fine grind­
ing compound. The refacing and reseating should
leave the refinished surfaces smooth and true so that a minimum of lapping
will
be required. Ex­
cessive lapping
will
groove the valve face and pre­
vent
good
valve seating.
e. Test valve seats for concentricity with guides,
and
for proper valve seating. Coat a small segment
of the valve face lightly with Prussian blue pig­ ment.. Insert the valve stem into its guide and

turn
the valve face against the seat. If the valve seat is concentric with the valve guide, a
mark

will
be made all around the seat. If the seat is not concentric with the guide, a
mark
will
be made
on only one side of the seat.

Clean
all pigment from both valve and seat. .Next,
coat a small segment of the valve seat lightly with

Prussian
blue pigment. Again insert the valve stem into its guide and rotate the valve face against the
seat. If the valve face is concentric with the valve
stem, and if the valve is seating all the way around,
pigment
will
coat the valve face with a uniform
band
around its entire perimeter. Both of
these

tests
are necessary to prove that proper valve seat­
ing is obtained.
f. Inspect the valve springs visually for corrosion,

breaks,
and distortion.
With
a valve spring tester
check
each valve spring for proper tension. When

a
valve spring is compressed to a length of
1.640"
[4,166 cm.] (closed-valve condition), it should
have a tension of 64 lb. [29,03 kg.]. When a valve
spring
is compressed to a length of
1.260"
[3,200
cm.] (open-valve condition), it should have ten­ sion of 168 lb. [76,205 kg.]. Replace any valve
spring
which is visibly damaged or
does
not
meet

tension specifications.

Dl-64.
Valve Installation

Lubricate
valve stems with engine oil.
Install
valves, valve springs, spring retainers, and valve

retainers
on the cylinder head. Use the same equipment and reverse procedure used for removal.

Install
valve springs with closely wound coils to­

ward
the cylinder head. Refer to Fig. Dl-29.
FIG.
Dl-29—VALVE
SPRING

1—
Spring

2—
Close
Wound
Coils
Toward
Head
94

Dl

DAUNTLESS
V-6
ENGINE
Note:
During
engine
reassembly, use Perfect Seal

Aerosol
Spray Sealer
Part
No.
994757
on all en­
gine
gaskets to ensure against vacuum, oil, gasoline

and
water leaks. Apply to head gaskets, valve covers, water pumps, oil pan gaskets, radiator and
heater
hose
connections, felt gaskets, gasoline and
oil
line connections, stud bolts, spark plug threads,

and
grease retainer washers. Refer to manufac­
turer's
instructions on container for proper appli­
cation procedure.

Dl-72.
Cylinder
Block
and Crankshaft
Rear
Oil Seals

Braided
fabric seals are pressed into
grooves
of
cylinder
block and
rear
main bearing cap, to
rear

of the oil collecting groove, to seal against oil leak­ age at the crankshaft. Refer to Fig. Dl-32.

FIG.
Dl-32—INSTALLING
CRANKSHAFT REAR
OIL
SEAL

1—Neoprene
Seal
2—Fabric
Seal

A
neoprene composition (stick) seal is installed in
grooves
in the sides of the
rear
main bearing cap
to seal against leakage in the joints
between
the
cap and cylinder block. The neoprene composition
expands in the presence of oil and heat.
This
seal
is undersize when newly installed. Refer to Fig.

Dl-32.

a.
The braided fabric seal can be installed in the

cylinder
block only when the crankshaft is re­ moved; however, the seal in the cap can be replaced
whenever the cap is removed. Remove oil seal and place new seal in groove, with both ends projecting
above parting surface of cap. Force seal into
groove

by rubbing down with hammer handle or smooth
stick
until seal projects above the
groove
not more

than
[1,59 mm.]. Cut ends off flush with
sur­

face of cap, using sharp knife or razor blade.
Lubricate
the seal with heavy
engine
oil just before
installation.

Caution:
The
engine
must be operated at slow
speed when first started after new braided seal
has been installed.
b. The neoprene composition seal is slightly longer

than
the
grooves
in the bearing cap. The seal must
not be cut to length. The seals are installed after the bearing cap is installed in the block and torqued
firmly
in place. Dip the neoprene seals in kerosene
approximately IV2 minutes, then install seals into
bearing cap grooves. The protruding ends of the seals are, again, squirted with kerosene, wiped off,

and
peaned over with a hammer to be sure of a
seal
at the upper parting line
between
the cap and

cylinder
block.

Dl-73.
Main
Bearing and Crankshaft
Installation

Refer
to Fig. Dl-6.

This
procedure assumes that crankshaft main bear­
ings have been inspected and proven satisfactory,

or
that new crankshaft main bearings of appropriate size have been selected. If necessary, check or select
main
bearings as described in Par. Dl-41 and
Pars.

Dl-42 and Dl-43.

a.
Install
four upper main bearing halves in
seats

of cylinder block so that prong of each bearing half
fits into corresponding notch of seat. Flanged thrust
bearing must be installed in the second seat from
front of engine.
Install
a new upper crankshaft
rear
oil seal in the cylinder block as described in

Par.
Dl-72.

Caution:
Upper main bearing halves have an oil groove, while lower halves are plain. They must
not be interchanged.
b. Apply
engine
oil to upper bearing surfaces.

Install
the crankshaft so that its four journals rest

in
the upper bearing halves.
c. Seat all four lower main bearing halves in cor­
responding bearing caps.
Install
a new lower
crank­

shaft
rear
oil seal and cylinder block
rear
oil seal
described in
Par.
Dl-72, a and b.
Lubricate
all lower

main
bearing surfaces with
engine
oil. Position bear­ ing caps to cylinder block and crankcase journals.

Install
two cap bolts,
loosely,
at each cap.

d.
It is necessary to align thrust surfaces of the
second main bearing whenever it has been removed

from
the engine. To do this, pry the crankshaft

back
and forth several times, throughout its entire end travel, with cap
bolts
of second main bearing
only finger tight.
e. Tighten alternate cap
bolts
of each main bearing

cap,
a little at a time, until they have been tight­ ened to 80 to 110 lb-ft. [11,1 a 15,2 kg-m.] torque.
D1-74. Crankshaft End Play Check

To
measure crankshaft end play, mount a dial
indicator
on the cylinder block and index its plung­

er
to either a front or
rear
face of one crankshaft
counterweight. Pry the crankshaft to one limit
of its end travel and adjust the dial indicator to
zero. Pry the crankshaft to its
opposite
end travel

limit
and
note
end play as indicated by the dial

indicator.
Crankshaft end play tolerances are .004"
to .008" [0,102 a
0,204
mm.]. If end play is too great, it can be corrected only by replacement of
the second main (thrust) bearing.

Dl-75.
Piston and Connecting Rod
Installation

This
procedure assumes that connecting rod bear­ ings have been inspected and proven satisfactory,

or
that new connecting rod bearings of appropriate 96

E

FUEL
SYSTEM
Note:
Do not remove pressed-in parts such as
nozzle, pump jet, or antipercolator air bleed.

j.
Remove body flange attaching screws, body flange assembly, and gasket.

k.
Remove idle-adjustment screw, spring, idle

port
rivet, throttle lever assembly, washer, fast
idle arm, throttle plate screws, throttle plate, and throttle shaft.
1. Remove throttle shaft seal by prying out seal

retainer.

Note:
Do not remove pressed-in vacuum passage

orifice.

m.
Remove choke valve screws and choke valve.

Unhook
choke spring and slide shaft from housing,
n.
Wash all parts in carburetor cleaning solution

and
blow out passages with compressed air. Do not immerse diaphragm or seals in cleaning solution.

Inspect
all parts for wear or damage. Always use
new gaskets when reassembling.

E-22.
Carburetor
Reassembly

•
Refer to Fig. E-13.

To
expedite
reassembly, it is advisable to group all

related
parts by the circuit to which they belong.

a.
Install
throttle shaft seal and retainer in flange casting.

b.
Install
fast-idle
arm,
washer, and lever assembly
on throttle shaft. Slide shaft into place and install throttle valve.

c.
Install
idle port rivet plug and idle adjusting

screw
and spring.

d.
Attach flange assembly to body casting. Use new gasket.
e.
Install
low-speed jet assembly.
f.
Early
production models install pump intake
strainer
in pump diaphragm housing and carefully
press into recess.

Note:
If strainer is even slightly damaged, a new
one must be installed.
g.
Install
pump diaphragm assembly in diaphragm housing.
Then,
install pump diaphragm spring
(lower)
and retainer.

h.
Install
pump lifter
link,
metering rod
arm,
upper
pump spring, and retainer.

I.
Install
metering rod jet.

Note:
No gasket is used with this jet.

j.
Install
diaphragm housing attaching screws in
the diaphragm housing, making sure that the

edges
of the diaphragm are not wrinkled.
Lower

into place and tighten screws evenly and securely,
k.
Install
throttle shaft seal, dust seal washer, and
shaft seal spring.

I.
Install
pump connector
link
in the throttle arm
assembly.
Install
throttle shaft arm assembly on
throttle shaft guiding connector
link
in pump lifter

link
hole.
CAUTION:
Linkage
must not bind in any throttle
position. If binding occurs,
loosen
clamp screw in
throttle arm, adjust slightly, then retighten screw.

m.
Install
pump check disc, disc retainer, and lock

ring.

n.
Install
metering rod and pin spring. Connect
metering rod spring.
o.
Check
and if necessary correct meter ing rod adjustment. Follow procedure of
Par.
E-16.
p.
Install
needle
seat and gasket assembly, needle,
float
and
float pin. The
stop
shoulder on the float
pin
must be on the side away from the bore of
the carburetor.

q.
Set float level to specifications. Follow pro­ cedure of
Par.
E-12.

r.
Install
air horn gasket and air horn assembly.

Install
attaching screws, lock washers, and choke
tube clamp assembly. Tighten center screws first,
s. Slide choke shaft and lever assembly into place
and
connect choke lever
spring.
Install
choke valve.
Center
the valve by tapping lightly, then hold in
place with fingers when tightening screws,
t.
Install
fast-idle connector rod with
offset
portion
of rod on top and pin spring on outside.
Install
fast-idle connecting rod spring.

E-23.
Correcting Acceleration
Flat
Spot

Early
production
Carburetor
Models 938-S, 938-
SA,
938-SC

Inasmuch
as a flat
spot
on acceleration or low speed
stumble can
come
from causes other than
car­

buretor
malfunction, it is recommended that
engine

tuning be thoroughly checked before attempting
any
actual carburetor work. Make sure that
ignition, compression, and timing are correct and
that fuel pump is supplying enough gas. Also, the F-head
engine
employs a water-heated intake

manifold.
Proper vaporization of the fuel depends
on correct intake manifold temperature. Since this
temperature is controlled by the cooling system
thermostat, include an operational check of the
thermostat when diagnosing the stumble. Operating
temperatures consistently below
155°F.
can cause stumble.

If
the stumble persists, a
YF-938-S,
YF-938-SA,

or
YF-938-SC
carburetor can be converted to a
YF-938-SD
carburetor by installing Special Kit
924161, consisting of a pump discharge check
needle, a metering rod, and a metering rod jet. If this kit is installed, the pump discharge check

needle
replaces the original
ball,
weight, and re­

tainer
and the small wire-type retainer used with
the
ball
check assembly must not be reinstalled.

When
installing the kit, check the size of the pump discharge jet, No. 2, Fig. E-14.
Early
production
YF-938S
and
YF-938SA
carburetors have a .025" [0,635 mm.] jet installed. If the carburetor being
converted has a .025" jet it must be opened up to .031" [0,787 mm.] by running a No. 68
drill
through
the jet as shown in
Fig.
E-14.
The jet must be drilled
as it is a pressed in part and cannot be replaced.
Upon
completing the installation of the conversion

kit,
mark
or tag the carburetor to indicate that it
is a
YF-938SD.
118

'Jeep'
UNIVERSAL SERIES SERVICE
MANUAL

FIG.
E-19—
MAIN
METERING SYSTEM
1—
Main
Nozzle
2—
Mixture
Passage

3—
Boost
Venturi

4—
Main
Venturi

5—
Throttle
Valve 6—
Main
Metering Jet
7—
Main
Well
Insert
8—
Main
Well
Tube
9—
Main
Well
Air Bleed fuel through calibrated
holes
in the main well tube.

Fuel-air
mixture then
moves
upward into a channel
where another calibrated amount of air is injected through the main air bleed. It then flows down­

ward
through the channel to the venturi, where it is discharged into the air stream, and then to the
intake manifold.

E-29.
Power System

A
vacuum-operated power piston in the air horn
and
a power valve in the
bottom
of the float bowl

enrich
fuel-air mixture when more power is desired.

This
system also operates during extreme high
speed driving. Through a vacuum passage from the
carburetor
base to the power cylinder, the power
piston is
exposed
to manifold vacuum. See Fig.

E-20.

During
idle and part throttle operation, relatively
high vacuum holds the power piston in upward
FIG.
E-20—POWER
SYSTEM
position against spring tension so that the power
valve remains closed.

Increase
in
engine
load decreases manifold vacuum.

When
vacuum decreases sufficiently, the spring
overcomes vacuum and the power piston
moves
downward.
This
opens
the power valve to allow
additional fuel to flow through calibrated restric­
tions into the main well.

As
the
engine
load decreases, resulting higher

vacuum
overcomes spring tension on the power
piston and draws the power piston upward.
This

closes
the power valve.

This
carburetor has a
two-stage
power valve. In
the first
stage,
fuel is metered by the valve itself.
This
stage
occurs under light load. During heavy

load,
the valve is fully opened to the second
stage;

in
this position, the power valve supplies fuel to
be metered by power restrictions in the fuel chan­

nel
to the fuel bowl.

The
power piston cavity is connected to the main

air
flow passage by a vacuum relief passage.
This
passage prevents transfer of vacuum to fuel in the
float bowl. Any leakage of air past the piston
will

be compensated for by this relief passage; hence it

will
not affect carburetor metering.

E-30.
Accelerator Pump System

When
the throttle valve
opens
rapidly, air flow

and
manifold vacuum change almost instantaneous­

ly.
However, heavier fuel-air mixture
does
not flow immediately.
Thus,
momentarily, the
engine
does

not have sufficient fuel. The accelerator pump pro­ vides additional fuel necessary for
engine
operation

during
acceleration.

A
double-spring loaded pump plunger supplies fuel for acceleration. Top and
bottom
springs
move
the
plunger to furnish a smooth, sustained charge of
fuel for acceleration. See Fig. E-21.

Fuel
is drawn into the pump well past the inlet
check ball during the plunger intake (upward)
stroke.
Downward
motion of the pump plunger
seats
the
inlet check ball and forces fuel through the dis­ charge
passage.
This
unseats
the pump discharge
check
ball.
Fuel
then sprays through the discharge
12837

FIG.
E-21—ACCELERATOR
PUMP
SYSTEM

1— Piston Vacuum Chamber
2—
Vacuus*
Relief Passage

3—
Main
Well

4— ^Power Restrictions 5— Power Valve
6— Power Piston Spring 7— Power Piston 1— Pump
Jets

2—
Discharge
Check
Ball

3—
Discharge
Passage
4—
Inlet
Check
Ball
5—
Inlet
Screen
6—
Vapor
Vent
Check
Ball

7—
Pump
Plunger
121

'Jeep'
UNIVERSAL
SERIES
SERVICE
MANUAL

E
E-47.
Reassembly

•
Refer to Fig. E-29.
Install
the valve gaskets, valves, valve retainer and
secure them with the valve retainer screws. Make
sure that the inlet and
outlet
valves are in their proper positions. Place the diaphragm spring re­
tainer in position on the diaphragm
pull
rod
and
install diaphragm spring. Position the
dia­

phragm assembly in pump
body
and attach the
cover to pump body, with file marks aligned, with
the six attaching screws. Do not draw the screws
up tight.
Install
rocker arm spring, rocker arm

pin
washers, rocker arm and rocker arm pin.
With

rocker
arm positioned on the diaphragm rod, draw
the six pump
body
screws up evenly and securely.
Install
the filter screen, cork gasket and sediment
bowl and secure them firmly with the thumb screw
on the bowl clamp.

E-48.
Vacuum
Pump

The
double-action fuel pump resembles two single-
action pumps placed one
above
the other. A single
fuel pump rocker arm actuates the two separate diaphragms. One diaphragm is part of the fuel
delivery pump and operates as described in Par.
E-45.
The other diaphragm is part of the vacuum
pump and operates as described here.

As
the actuating lever forces the diaphragm upward against spring pressure, air is forced through the

outlet
port
into
the
engine's
intake manifold. On
the return stroke, spring pressure forces the
dia­
phragm downward, creating a
partial
vacuum and
opening the inlet valve. In this manner, air is pumped out of the windshield wiper motor and
into

the intake manifold. When the wiper motor is shut off, manifold vacuum holds the diaphragm against its spring so that the
full
motion of the actuating
lever is not accompanied by a
complete
up-and-
down motion of the diaphragm.

When
the windshield wiper motor is turned on, but manifold vacuum is greater than the vacuum
created by the
booster
pump, air
flows
from the
wiper motor through both valves of the vacuum
booster.
As manifold vacuum drops off as a result
of the
engine
operating under low
speed
and high load, the vacuum created by the vacuum
booster

will
be greater than
engine
intake manifold vacuum

and
the pump
will
operate the wiper motor when the wiper control switch is turned on.

•
Refer to Fig. E-29. Remove the
eight
cover attaching screws and
lockwashers, and remove the cover, diaphragm

spring
and spring seat. Detach the diaphragm rod
from the rocker arm and remove the diaphragm.
The
valve assemblies are pressed
into
the cover

and
body
and lightly staked. They may be removed
with the point of a knife blade. If installing new valves be sure the inlet and
outlet
valves are
correctly positioned and stake them lightly with

a
small punch.
Assemble the vacuum pump in the reverse order
of disassembly, drawing the cover attaching screws up evenly and tightly.
E-49.
Fuel
Pump
Testing

Four
tests
are presented in following paragraphs to
test
for proper operation of the fuel pump. In addi­
tion, check the following:

a.
Check
for secure mounting of the fuel pump.

The
rocker arm may be working the entire pump
up and down, rather than just the pump
dia­

phragms.
b. Remove and clean the fuel sediment bowl.
c.
Check
all fuel lines.
E-50.
Volume
Check

To
measure fuel pump capacity (amount of fuel
delivered in a given time) disconnect the pump-to-

carburetor
line at the carburetor end. Place the

open
end of the line in a suitable container.
Start

the
engine
and operate at normal idle speed.
Delivery
should be one quart U.S. [1 ltr.] within
one minute.

E-51.
Pressure
Check

To
measure fuel pump pressure (force of fuel de­

livery)
disconnect the pump-to-carburetor line
at the carburetor end. Plug a pressure
gauge
and T-fitting
into
the
open
end of this line and
into
the

carburetor.
Start
the
engine
and operate at normal
idle speed. Pressure should be 2J4 to 3% psi.
[0,716
a
0,264
kg-cm2] at 1800 rpm. and at 16"
[406 mm.]
above
the
outlet.

E-52.
Vacuum
Check

To
measure fuel pump vacuum (pull of. the pump
at the inlet side) disconnect the pump-to-fuel-tank
line at the fuel pump. Attach a vacuum
gauge
to the fuel pump inlet.
Start
the
engine,
accelerate to
specified speed, and hold this
engine
speed
while
taking a
gauge
reading. Permissible
gauge
reading
is 8* [203 mm.] of mercury [Hg] at 1200 rpm. and
10j^'
[267 mm.] at 1800 rpm.
E-53.
Vacuum
Booster
Check

To
test
the condition of the vacuum
booster
pump,
disconnect both inlet and
outlet
lines at the pump.

Attach
a vacuum
gauge
to the windshield wiper
connection at the pump.
Start
the
engine,
accelerate
to
2000
rpm., and hold this
engine
speed
while taking a
gauge
reading. Permissible
gauge
reading
is 10* to 14" [254 a 356 cm.] of mercury [Hg].
E-54.'
FUEL
PUMP
(SINGLE-ACTION)
—
HURRICANE
F4
ENGINE
•
Early
Models.
Vehicles with electric windshield wiper motors are
equipped with a single-action fuel pump (Fig.

E-30).
The fuel pump cam lever is activated by an eccentric on the
engine
camshaft. When the
car­

buretor float
needle
valve closes, accumulation of
fuel in the pump
extends
the diaphragm spring.

This
action causes the rocker arm linkage to be­
come
inoperative until the pressure on the
dia­
phragm and spring is reduced. The fuel pump dis­
charge pressure is thus controlled by the diaphragm

spring.
This
provides a steady supply of fuel to the
carburetor
at a fairly constant pressure. 127