engine JEEP CJ 1953 Service Manual

'Jeep*
UNIVERSAL
SERIES
SERVICE
MANUAL

Dl
Dl-105.
DAUNTLESS
V-6
ENGINE
SPECIFICATIONS—Continued

CONNECTING
RODS:
Material
Installation
Bearings: Type........
Material.
Length Clearance

End
Play
(total
for two
connecting
rods)

CRANKSHAFT:
Material ,

End
Thrust
End
Play

Main
Bearings: Number Type
Material:
Length, Over-All: No. 1, No. 3, and No. 4
No. 2
Clearance

Main
Journal Diameter.
Crankpin
Journal Diameter
Flywheel Run Out, max

CAMSHAFT:
Material
Bearings: Number Material Clearance

Journal
Diameter: No. 1 No. 2
No. 3.
No. 4
Location Camshaft Drive

Chain
Links
Camshaft Sprocket Material
Crankshaft Sprocket Material

VALVE
SYSTEM:
Valve Lifters Diameter Clearance in Cylinder Block
Leak-down Time
(seconds)

Rocker Arms: Ratio Clearance on Shaft
Valves: Intake: Material
Head Diameter

Seat
Angle
Stem
Diameter

Stem
Clearance in Guide
Exhaust:
Material Head Diameter

Seat
Angle
Stem
Diameter

Stem
Clearance in Guide
Valve Springs — Pressure at Length: Valve Closed English
Pearlitic Malleable Iron

From
Top of Cylinder Bore
Removable, Steel-Backed Aluminum .737"

.0020"
to
.0023"
.006" to .014" Metric
18,72 mm.

0,0508
a
0,0584
mm. 0,153 a
0,356
mm.
Pearlitic Malleable Iron
Second
Main Bearing .004" to .008"

Removable

Moraine 100
.864"

1.057"

.0005"
to
.0021"
2.4995"

2.0000"

.015" 0,102 a
0,203
mm.
21,95 mm.

2,685
cm.

0,0127
a
0,0533
mm.
6,349
cm.
5,080
cm.
0,381 cm.

Cast
Iron Alloy
Steel-Backed Babbitt
.0015"
to
.0040"

1.755"
to
1.756"

1.725"
to
1.726"

1.695"
to
1.696"

1.665"
to
1.666"

In
Cylinder Block, at Center of V
Chain
and Sprocket 54
Aluminum,
Nylon
Coated Sintered Iron
0,0381
a
0,1016
mm.

4,458
a
4,460
cm.
4,382
a
4,384
cm.
4,305
a
4,307
cm.

4,229
a 4,231 cm.
Hydraulic

.8422"
to
.8427"

.0015"
to
.0030"
12 to 60
1.6:1

.0017"
to
.0032"

Steel,
SAE 1041
1.625"
45°

.3415"
to
.3427"
.0012"
to
.0032"

GM-N82152
(21-4N)
1.3750"
45°

.3402"
to
.3412"
.3397"
to
.3407"

.0015"
to
.0035"
(top)
.002" to .004"
(bottom)

1.640"
at 59 - 64 lb.
1.260"
at 168 lb. 21,39 a 21,40 mm.

0,0381
a
0,0762
mm.

0,0432
a
0,0812
mm. 4,128 cm.

8,674
a
8,704
mm.

3,4925
cm.
8,641 a
8,666
mm.

8,628
a
8,653
mm.

0,0381
a
0,0889
mm. 0,051 a 0,102 mm.
4,16 cm. at
26,76
-
29,03
kg. 3,20 cm. at
76,20
kg.
107

Dl

DAUNTLESS
V-6
ENGINE
D1-10S. DAUNTLESS V-6 ENGINE SPECIFICATIONS—Continued

LUBRICATION SYSTEM:
Type of Lubrication:

Main
Beasings
Connecting
Rod Bearings

Piston
Pins. Camshaft Bearings
Rocker Arms
Timing
Chain

Cylinder
Walls

Oil
Pump: Type
Drive
Normal Oil Pressure
Oil
Pressure
Sending
Unit. .

Oil
Intake
Oil
Filter
System

Filter
Type

Crankcase
Capacity:
Without
Filter

With
Filter.
English

Pressure
Pressure Splash
Pressure
Pressure
Splash and
Nozzle
Splash and
Nozzle

Gear

Camshaft Gear

33
psi. at
2400
rpm.
Electrical

Screened
Tube

Full
Flow Type
Throwaway Element and Can
4 qt.
5
qt. Metric
2,32 kg-cm2 at
2400
rpm.
3,8
ltr.
4,7 ltr. 108

'Jeep*
UNIVERSAL SERIES SERVICE
MANUAL

E

FUEL
SYSTEM
Contents

SUBJECT
PAR.

GENERAL
E-1 Dash

FUEL
EVAPORATIVE EMISSION
?*^r
CONTROL SYSTEM
..E-2
Canister
.E-3 . Demand Valve E-4

Fuel
Tank.
.E-5
Inspection Test. E-8
Sealed Gas Cap. E-7

Servicing
System E-9
Vapor
Separator or Expansion
Tank
E-6

CARBURETOR
—
HURRICANE F4 ENGINE.
. .
......
..... ,. . .E-10 Accelerating Pump System.............. .E-19 Accelerating Pump Maintenance E-20

Carburetor
Reassembly
E-2
2

Carburetor
Disassembly E-21
Choke
System E-17
Dash
Pot Adjustment E-44

Fast
Idle Adjustment E-18
Float
Adjustment E-12
Float
System. E-ll
High-Speed System . .E-15
Idle
Adjustment .E-14

Low-Speed
System . E-13
Metering Rod Adjustment E-16

CARBURETOR
~r
DAUNTLESS V-6 ENGINE
.E-25
Accelerator Pump Adjustment E-41 Accelerator Pump System. . E-30

Air
Horn Body Assembly E-39
Air
Horn Body Removal and Disassembly.
E-33

Carburetor
Cleaning and Inspection E-36
Carburetor
Removal E-32
Choke
System E-31

Curb-Idle
Speed and Mixture Adjustment. .E-42

E-1. GENERAL
The
fuel system of the Jeep Universal vehicle,
whether equipped with a Hurricane F4 or Daunt­

less
V-6 Engine,
consists
of the fuel tank, fuel lines, fuel pump, carburetor and
air
cleaner.
Fig. E-1, E-2.
Vehicles equipped with a
Fuel
Evaporative
Emis­

sion Control System
also
include a
non-vent

pressure and vacuum
sensitive
gas cap, a liquid
expansion and vapor separator tank, a carbon filled vapor
storage
canister, and a vapor purge line. Service information pertaining to the
Fuel
Evap­

orative Emission Control System is outlined in

Par.
E-2 through
E-9.
Refer to Figs. E-3 and E-4.
The
most
important
attention
necessary to the fuel
system is to
keep
it clean and free from water. It should be periodically inspected for leaks.

CAUTION—Whenever
a vehicle is to be stored for

an
extended
period, the fuel system should be com­

pletely
drained, the
engine
started and allowed to
run
until the carburetor is emptied.
This
will
avoid
oxidization of the fuel, resulting in the formation of
SUBJECT
PAR.
Pot Adjustment .E-44

nal
Carburetor Adjustments.........E-40

Idle
Adjustment
.
E-43 System . . .E-26

Bowl
Body Assembly E-38

Fuel
Bowl Body Disassembly E-34

Idle
System E-27

Main
Metering System E-28
Power System . E-29
Throttle
Body Assembly .E-37

Throttle
Body Removal, and Disassembly. .E-35

FUEL
PUMP
—
HURRICANE F4 ENGINE.
E-45, 54, 60

Cleaning
and Inspection.............
.E-57,
63 Disassembly E-46, 56, 62
Installation E-59, 65
Reassembly
.E-47,
58, 64
Removal
E-55, 61

Testing.
E-49, 50, 51, 52, 53, 66

Vacuum
Pump E-48

FUEL
PUMP
—
DAUNTLESS V-6 ENGINE
E-67
Removal
E-68

AIR CLEANER
—
CARBURETOR
E-69
ACCELERATOR
LINKAGE
.E-70

FUEL
TANK
AND
LINES
E-71
Float
Unit . .E-76
Fuel
Lines E-77
Fuel
Tank
. . .E-72

Fuel
Tank
Cap E-75

Fuel
Tank
Installation. E-74
Fuel
Tank
Removal E-73

SERVICE
DIAGNOSIS
E-78

SPECIFICATIONS.
E-79
gum in the units of the fuel system. Gum formation
is similar to hard varnish and may cause the fuel
pump valves or the carburetor
float
valve to be­
come
stuck or the filter screen blocked. Acetone or commercial fuel system cleaners
will
dissolve

gum formation. In
extreme
cases
it
will
be necessary
to dissassemble and clean the fuel system. In
most

cases, however, a
good
commercial fuel system sol­
vent
used in accordance with the manufacturer's
instructions or one pint [0,6 ltr.] of
acetone
placed
in
the fuel tank with
about
one gallon [4,5 ltr.]
of
gasoline
will
dissolve
any
deposits
as it
passes

through the system with the
gasoline.

E-2.
FUEL
EVAPORATIVE EMISSION CONTROL SYSTEM

Description and Operation

•
Refer to Figs. E-3 and E-4.

The
Fuel
Evaporative Emission Control System
is
designed
to reduce fuel vapor emission that 109

E

FUEL
SYSTEM

FIG.
E-1—FUEL SYSTEM—EARLY MODEL—F-4 ENGINE 1—
Fuel
Line
To Carburetor 4—Accelerator Treadle
2— Carburetor 5—Fuel Tank and Gauge
3— Choke Cable 6—Fuel Pump

FIG.
E-2—FUEL SYSTEM—EARLY
MODEL—V-6
ENGINE 1—
Fuel
Line
To Carburetor 5—Fuel Tank and Gauge

2—
Carburetor 6—Fuel Pump
3— Choke Cable 7—Fuel
Line
To Fuel Pump

4—
Accelerator
Treadle 8—Fuel Return
Line
normally
vents
to the atmosphere from the vehicle
fuel system.

The
fuel vapor system consists of internal fuel tank
venting, a vacuum /pressure fuel tank cap, a vapor
separator or expansion tank, vapor canister, and closed external carburetor venting. The same basic
system is used on all 'Jeep' vehicles, as shown in
Fig. E-3.

This
system involves means of trapping the fuel
vapors through the use of a charcoal canister which
absorbs the vapor and stores it until it can be re­ moved to be burned in the
engine.
This
removal is
performed by drawing
these
vapors through the purge line
into
the crankcase ventilation system

which
in
turn
enters the intake manifold. In ad­ dition to the canister, the fuel tank requires a sealed
gas cap and extra
vents
to a liquid separator or
expansion tank.
This
prevents liquid
gasoline
from entering the vapor system.
Thus,
as vapors are generated in the fuel tank,
they
flow through the

liquid
separator or expansion tank to the canister

and
are routed to the intake manifold through the 110

'Jeep*
UNIVERSAL
SERIES
SERVICE
MANUAL

E

FIG.
E-3—FUEL EVAPORATIVE EMISSION CONTROL SYSTEM- HURRICANE F4 ENGINE
A—Side
View

1—
Charcoal Canister
2— Purge
Line

3—
Fuel
Tank
4—
Fuel
Filler
Hose 5—
Non-Vented
Gas Cap
B—Plan
View

6—
Vapor
Separator
or Expansion Tank 7—
Fuel
Gauge

8—
Fuel
Line-to-Fuel Pump

9—
p.C.V.
Crankcase
Valve

10—Fuel
Pump

crankcase
vent system. The charcoal canister in­
corporates an integral demand valve
which
regu­

lates
vapors entering the canister as
well
as a
limit
fill
valve
to control air trapping during tank
fill.
The
Fuel
Evaporative Emission Control System
incorporates the following new or modified parts:

E-3.
Canister
The canister used for the vapor control system has
provisions for containing activated charcoal gran­ ules. The material used for the canister body is a

special,
fuel resistant, heat stabilized nylon. At the top of the canister there is the demand valve which
has connections; one vents the vapor to the canister
while the other connection joins the canister to the purge system. These
tubes
enter the canister on

opposite
sides of a baffle which permits uniform
vapor distribution throughout the canister. The
bottom
of the canister is fitted with a filter element
that allows fuel tank venting to atmosphere after vapors are trapped in the activated charcoal.

E-4.
Demand Valve

The
demand valve is integral with the canister. It
is essenitally a combination pressure regulator and

vacuum
relief valve.
This
valve regulates the rate
of vapor
flowing
from the fuel tank into the canister.
The
valve consists of a housing, a spring loaded
diaphragm,
a diaphragm cover, and a vacuum

relief
valve. The operation of the unit is such that
as tank vent pressure increases the diaphragm lifts,
permitting vapor to enter the canister. The pres­
sure
under which this occurs is 4" to 6"
H2O.
This

action regulates the flow of vapors into the canister
under severe soak and operation conditions (temp, changes), but generally prohibits the flow of vapor 111

E

FUEL
SYSTEM

9
©

FIG.
E-4—FUEL
EVAPORATIVE
EMISSION
CONTROL
SYSTEM-
DAUNTLESS
V-6
ENGINE
A—Side
View
1—
Charcoal
Canister

2—
P.C.V.
Crankcase
Valve

3—
Purge
Line

4—
Fuel
Tank
5—
Fuel
Filler
Hose
B—Plan
View
6—
Non-Vented
Gas Cap 7—
Vapor
Separator or Expansion
Tank

g—Fuei
Gauge

9—Fuel
Line-to-Fuel
Pump

10—Fuei
Return
Line

during
normal temperature vehicle operation, thus
minimizing
driveability problems. An additional
feature of this valve is a built-in vacuum relief

which
allows inward air flow under negative fuel

tank
pressure conditions. The valve housing con­
tains the normal tank vent and purge connections.

E-5.
Fuel Tank

The
fuel tank is external expansion type.
Fuel

tank
venting is accomplished by several vapor
lines which lead to the vapor separator or expan­
sion tank. The vapor lines which lead from the
fuel tank are located at the front and
rear
so that
during
any inclination of the vehicle, at least one
line
will
be open to vent at all times.
E-6.
Vapor Separator
or
Expansion Tank

The
vapor separator is chambered so that the
rear
fuel tank vent lines lead into a separate chamber

with
a fuel shutofl valve.
This
prevents solid fuel
from
flowing from the fuel tank to the vapor can­
ister during uphill operation or parking of the
vehicle. A single vapor vent line leads from the fuel
vapor separator to the vapor collection canister
where fuel vapors are stored until they can be drawn into the
engine
and burned.

The
expansion tank allows expansion of the fuel as

required
during temperature changes and simul­ taneously
becomes
a liquid trap that only allows
vapors to pass.
E-7.
Sealed
Gas Cap

The
sealed gas cap is designed to allow no vapors to
discharge into the atmosphere under normal
operation of the system. If the system
becomes
plugged or a failure of the demand valve occurs 112

'Jeep*
UNIVERSAL
SERIES
SERVICE
MANUAL

E
there is a relief valve that
opens
to reduce high
(dangerous) pressures in the fuel tank. In con­

junction
with the pressure relief valve there is a
vacuum
relief valve to
stop
collapse of the fuel

tank
in case of a plugged system or failure of the demand valve. When replacing the gas cap, the
same type must be used as originally installed.

E-8.
System Inspection Test

The
fuel emission vent system should be checked

carefully
to ensure the absence of any leaks to the
atmosphere of either liquid or vapor which might
affect the accuracy, safety, or performance of the control system.

To
assure that the sealed system has been properly

installed,
the following
test
procedure has been
developed.
Disconnect the vent line from the fuel tank system
to the activated charcoal canister, induce l/i p.s.i.
air
pressure. If this pressure can be maintained for

a
few seconds the vent system is assured to be sealed. DO NOT add air pressure to the canister
because damage can occur to the demand valve if
care
is not taken.

E-9.
Servicing the System

Periodic
Maintenance — Replace carbon canister filter at
12,000
miles
[19,200
km.] or 12 month in­tervals (more
often
for operation in dusty areas).

This
is the only regular maintenance service

required.

Canister
Filter
Replacement — Disconnect
hoses

from
top of canister, remove canister from mount
-

t
FIG.
E-5—CARBURETOR—
F4 ENGINE,
EARLY
MODEL
1—
Choke
Clamp
Bracket

2—
Choke
Shaft and
Lever
Assembly

3—
Fuel
Inlet
Elbow

4—
Bowl
Vent Tube 5—
Idle
Air Adjusting
Needle
6—
Throttle
Lever
and Shaft Assembly
7—
Idle
Speed Adjusting Screw
8—
Fast
Idle Connector Rod ing bracket. Remove cover from
bottom
of canister
by pulling it down to
disengage
clips. Remove and
discard
polyurethane filter element
(squeeze
ele­

ment out from under retainer bar).
Install
new
filter by squeezing element under retainer bar and positioning it evenly around entire
bottom
of
canister with
edges
tucked under canister lip, snap

bottom
cover in place, reinstall canister on bracket

and
reconnect
hoses.

Vapor
line
hoses
used in this system are made of

special
rubber material.
Bulk
hoses
are available for
parts
service.
Ordinary
rubber
hose
should not be
used to service vapor lines as they are subject to deterioration and may clog the system.
Liquid

vapor separators or expansion tanks and canisters

are
serviced as complete units only.
Canister
air filters, however, are serviced separately.

E-10.
CARBURETOR
—
HURRICANE
F4
ENGINE

A
single-barrel manual choke, down-draft carbure­
tor (Fig. E-6) is used on the
Hurricane
F4 engine.
The
carburetor is internally vented by a tube
opening located in the air horn body of the
car­

buretor.
This
opening is connected by a rubber
tube to the air
outlet
horn of the air cleaner thus
allowing only filtered atmospheric pressure air
to enter the float chamber for balance pressure
of the carburetor fuel.

Note:
A carburetor with a specific flow character­

istic
is used for exhaust emission control. The
carburetor
is identified by a number, and the correct

carburetor
must be used, when replacement is
necessary.

Early
production models
CJ-3B,
CJ-5,
CJ-5A,
CJ-6,
and
CJ-6A
have a
Carter
YF-938SD
carbure­
tor superseding the earlier
YF-938SC,
YF-938SA,

or
YF-938S
models.

Note."
Conversion kits for changing earlier models
to SD models are available. See Par E-23. It is recommended that when a carburetor is converted
that a tag be fashioned stamped with the new model number and installed under one of the air

horn
screws.
Look
for such a tag to determine if
the carburetor has previously been converted.

Carburetors
listed above are all in the same YF
series and have only minor differences. Descriptions
and
repair procedures given in the following
para­
graphs apply equally to all
YF-series
carburetors.
YF-series
carburetors employ manual and vacuum
control of the metering rod and accelerator pump.
The
carburetor controls and vaporizes the fuel
through five separate systems: float system, low-
speed system, high-speed system, choke system,

and
accelerating-pump system. A description of the function and operation of each system provides an over all description of the carburetor.

For
identification, the series designation is stamped
on the body under the name
Carter
and the model
designation is stamped on a flange protruding
from
the body.

Note:
When checking for carburetor icing causes,
also check the vacuum-pump-to-manifold vacuum
line connector. 113

FUEL
SYSTEM

14261

FIG.
E-6—CARBURETOR—
F4 ENGINE,
LATE
MODEL 1—
Choke
Clamp Bracket
2—
Throttle
Lever
and Shaft
3—
Choke
Shaft and
Lever

4—
Bowl
Vent Tube
5—
Fuel
Inlet Elbow
6—
Dash
Pot Bracket 7—
Throttle
Lever
8—
Dash
Pot Plunger
9—
Dash
Pot Assembly
10—
Lock
Nut
11— Stop Pin

1
2—Idle Mixture
Limiter
Cap
13—
Idle
Speed Adjusting Screw 14—
Fast
Idle Connecting Rod
E-11.
Float System

The
float system, Fig. E-7, consists of a float,
float
pin,
air horn gasket and the
needle
and seat assembly. These parts control the fuel level in the

carburetor
bowl, a supply being maintained for all
systems under all operating conditions. To prevent
float
vibration
from affecting the fuel level, the
inlet or float valve is spring loaded. Should the

needle
and seat
become
worn, they must be re­
placed
with a matched set, including the spring,

which
is the only way they are supplied. When
reinstalling
the float, be sure to install the float pin

with
the
stop
shoulder on the side away from the bore of the carburetor.

E-12.
Float Adjustment

Correct
float level setting is required for accurate
metering of fuel in both low- and high-speed jets.

To
set the float, remove and invert the bowl cover. Remove the bowl cover gasket. Allow the weight
of the float to rest on the
needle
and spring. Be

sure
there is no compression of the spring other

than
the weight of the float. Adjust the level by
bending the float arm lip that contacts the
needle
(not the arm) to provide specified clearance be­
tween the float and cover. The specified clearance of the float is
L74\F
[6,74 mm.] on current models
(including
Exhaust
Emission Control) and [7,93 mm.] on early models shown as A in
Fig.
E-8.
FIG.
E-7—FLOAT SYSTEM
1—
Float
and
Lever
Assembly
2—
Needle
Valve and Seat Assembly

3—
Vent

4—
Float
Bowl Cover 5—
Float
7 '.. j
io8Si
i

FIG.
E-8—FLOAT
LEVEL
GAUGING
E-13.
Low-Speed System

Fuel
for idle and early part-throttle operation is
metered through the low-speed system. The low-
speed system is illustrated in Fig.
E-9.
Liquid
fuel enters the idle well through the metering rod jet.

Low-speed
jet measures the amount of fuel for
idle and early part-throttle operation. Air-by-pass,
economizer, and idle air bleed are carefully
cali­

brated
orifices which serve to break up the liquid
fuel
and mix it with air as it
moves
through the passage to the idle port and idle adjustment screw

port.

E-14.
Idle Mixture Adjustment

Note:
The idle mixture adjustment procedure for
the late model
YF-4941S
and
YF-6115S
Carter
Carburetor
equipped with the
External
Idle

Mixture
Limiter
Cap is the same as outlined below 114

'Jeep*
UNIVERSAL
SERIES
SERVICE
MANUAL

E

FIG.
E-9—LOW-SPEED
SYSTEM

1—
Body
Flange 6—Idle Air Bleed

2—
-Idle
Adjustment Screw Port
7—Air
By-pass
3—
Idle
Port 8—Economizer

4—
Idle
Well
9—Metering Rod Jet
5—
Low
Speed Jet 10—Idle Adjustment Screw
in
Pars.
"A"
through
"D";
however, because of the

Idle
Limiter
Cap,
the idle mixture screw
CANNOT

be adjusted in the counter-clockwise
(rich)
direc­
tion. The adjustment is made from the
rich
stop

position and the mixture screw is turned in (clock­
wise) approximately %
turn
to
"Lean
Best
Idle."
Refer
to Fig. E-6.

The
"Lean
Best
Idle"
method of idle
setting
is as
follows:

a.
Any scheduled service of ignition system should precede this adjustment.

b.
Connect tachometer or vacuum
gauge
to
engine.

c.
Warm
up
engine
and stabilize temperatures.

d.
Adjust
engine
idle to
speed
desired, using throt­tle idle
speed
adjusting screw.
e. Carburetors without Idle
Limiter
Cap
turn
idle
mixture
screws out (counterclockwise) until a
loss

of
engine
speed
is indicated; then slowly
turn
mix­
ture
screw in (clockwise
-leaner)
until maximum

speed
(RPM) is reached. Continue turning in (clockwise) until
speed
begins
to drop;
turn
mixture
adjustment back out (counterclockwise
-rich)
until
maximum
speed
is just regained at a "lean as
possible" mixture adjustment.

E-15.
High-Speed System

Fuel
for part-throttle and full-throttle operation
is supplied through the high-speed system shown

in
Fig. E-10. A metering rod and metering rod

jet
control the amount of fuel admitted through the nozzle for high-speed operation. The lower
end of the metering rod is calibrated in size to

accurately
meter the fuel required. As the rod
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13346

FIG.
E-10—HIGH-SPEED
SYSTEM

1—Nozzle 7—Pump Diaphragm
Spring

2
—Metering
Rod 8—Diaphragm Assembly

3—
Pump
Lifter
Link
9—Chamber

4—
Metering
Rod Arm Assembly
10—Metering
Rod Jet 5—
Diaphragm
Shaft
11—Carburetor
Casting

6—
Upper
Pump Spring 12—Carburetor Bore is automatically raised and lowered in the jet,
the opening in the jet is varied in size to supply
fuel
proportionate to the requirements through the
higher
speed
and power range. The metering rod
is both mechanically and vacuum controlled and is
attached to the metering rod arm assembly.
During
part-throttle operation, vacuum in chamber

pulls
diaphragm down, holding metering arm
assembly against pump lifter
link.
Movement of the metering rod is controlled by the
pump lifter
link
which is attached to the carburetor
throttle shaft. At all
times
vacuum in the chamber
is strong
enough
to overcome the tension of pump

diaphragm
spring. Upper pump spring serves as

a
bumper upon deceleration and as a delayed
action spring upon acceleration. Under any operat­ ing condition, when the pump diaphragm spring
overcomes vacuum in the chamber, the metering

rod
will
move
toward the wide throttle (power) position.

Note:
Nozzle is pressed in and should not be
removed.

E-16.
Metering Rod Adjustment

Check
metering rod adjustment each time the

carburetor
is reassembled. Before adjustment is
made, be sure that the flat of metering rod arm
is parallel to the flat of pump lifter
link
as shown
(Fig.
E-10.).
With
the throttle valve
seated
in
car­

buretor
bore, press down on the upper end of
diaphragm
shaft until the diaphragm
bottoms

in
the vacuum chamber. The metering rod should
now
seat
on casting with the metering rod
arm
flat against the pump lifter
link.
If the meter­
ing rod
does
not
seat
on the casting (check by 115

E

FUEL
SYSTEM
pressing downward on metering rod) or
seats
be­
fore the metering rod arm makes flat contact with the pump lifter link, make adjustment by bending
the lip on the metering rod arm.

E-17.
Choke System

The
choke system consists of a manually-operated
choke valve, a fast-idle connecting rod, and a fast-
idle arm. The choke valve is offset-spring loaded to prevent over-choking during the starting warm-
up period. When the choke valve is moved to a closed position for starting, the fast idle connector

rod
in Fig. E-ll revolves the fast idle link.
This
action increases the
engine
idle speed to prevent stalling during the warm-up period. A fast-idle
connector rod return spring prevents partial closing
of the choke valve. pump lifter which is connected to the throttle.

This
movement forces fuel from the chamber
above the diaphragm through discharge pump check valve and discharge pump jet.
This
auxiliary discharge of fuel supplies
engine
requirements for

quick
acceleration and heavy loads. When the
throttle is closed, the diaphragm is again pulled
down by high vacuum and another measured
charge of fuel enters the chamber above the
diaphragm
through the intake passage to be
available for the next cycle of operation.

Note:
The pump jet (see insert drawing in Fig.

E-12)
projecting into the air stream is permanently pressed into the carburetor body and should not
be removed. Also, carburetor design makes it im­ possible to adjust the pump stroke.
FIG.
E-ll—FAST
IDLE
ADJUSTMENT

1—Fast
Idle
Connector Rod
2—Fast
Idle
Link
E-18.
Fast
Idle Adjustment

With
the choke held in wide open position, lip (No. 1) (Fig.
E-ll)
on the fast-idle rod should con­
tact the
boss
on the body casting. Adjust by bend­
ing the fast-idle link at
offset
as shown by (No. 2).

E-19.
Accelerating Pump System

The
accelerating pump system shown in Fig. E-12
provides a measured amount of fuel for rapid acceleration and smooth
engine
operation when
the throttle is opened at lower speeds. In operation,
vacuum
is applied to the underside of diaphragm
at all times when the
engine
is running.
Lower

and
more uniform vacuum is provided by vacuum
restriction
and vacuum bleed passage. When the
diaphragm
is in its maximum down position at
low throttle resulting from high vacuum in chamber the chamber above the diaphragm is full of fuel

which
has been admitted through intake passage.
When
the throttle is opened, vacuum drops in the
chamber and the diaphragm is initially forced
upward
by the spring on the diaphragm shaft.
The
upward motion is picked up by accelerator
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13347

FIG.
E-12—ACCELERATING
PUMP
SYSTEM

1—
Pump
Fuel
Passage
6—Intake
Passage

2—
Discharge
Pump Jet 7—Diaphragm

3—
Pump
Check
Valve
Ball
8—Vacuum Chamber 4—
Bail
Check
Weight
9—Vacuum
Restriction
Jet

5—
Pump
Lifter
Arm 10—Vacuum Bleed Passage
E-20.
Accelerating Pump Maintenance

If
engine
acceleration is unsatisfactory, remove the
pump diaphragm and check the diaphragm for wear

or
damage. Then remove the pump check retainer
ring
located directly above the pump check weight

and
pump ball check. Pump ball check must seat

properly
as a leak
will
cause poor acceleration performance. Inspect and replace all worn or
damaged parts.
Clean
and blow out all passages

with
compressed air.
Note
that when testing the pump for discharge volume with the carburetor
off the engine, only half of the maximum pump capacity
will
be discharged. When the
engine
is
operating, vacuum controls the balance of dis­ charge. 116