Jeep UNIVERSAL CJ-2A - Page 104

'Jeep' UNIVERSAL and 'Jeep' DISPATCHER
F
When installing the kit, check the size of the pump
discharge jet, No. 2, Fig. 129. 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. 129. The jet must be drilled
as it is a pressed in part and cannot be replaced.
FIG. 129-DRILLING CARBURETOR JET
1-Drill (#68 size)
2-Accelerator Pump Discharge Jet
Upon completing the installation of the conversion
kit, mark or tag the carburetor to indicate that it
is a YF -938SD.
F-28. Steep-Grade Carburetor Kit
In the field where a CJ-3B or CJ-5 equipped with
Carter carburetor 938-S is required to idle on steep
slopes, flooding of the carburetor sometimes results.
A steep-grade carburetor kit is available that will
allow satisfactory idle operation under this condi-
tion. This kit (W.M. #94481, Carter #75-960U)
contains a metering rod, a metering rod jet, and a
plug.
To install this kit, replace the standard metering
rod and metering rod jet with those contained in
the kit. Place the small brass plug in the accelerator
pump well. Exert finger pressure only when in-
stalling this plug. Forcing the plug in too far will
damage the accelerator jet. Make certain the meter-
ing rod and float, level are set to specifications. Set
idle at 600 rpm.
When reworking the carburetor to include this
steep-grade kit, check to determine if the seal
(Carter #121-172) and retainer (Carter #136-152)
are installed. If these parts are not present, they
should be installed.
F-29. Fuel Pump
• Models CJ-2A, DJ-3A
Fig. 130 illustrates the pump used on the Models
CJ-2A and DJ-3A. The rotation of the camshaft
eccentric operating rocker arm pivoted at the
rocker arm pin pulls the link and diaphra~m as-
sembly downward about X" [6,35 mm.], against
spring pressure which creates a vacuum in 1!"f111p
chamber to provide the suction stroke.
On the suction stroke of the pump, fuel from the
tank enters inlet into sediment bowl and passes
through strainer and inlet valve into pump
chamber. On the return stroke spring pressure
pushes the diaphragm upward forcing fuel from
chamber through outlet valve and out through
outlet to the carburetor.
10357
FIG. 130-FUEL PUMP-CJ-2A, DJ-3A
l--8trainer Bail and Seat
2-Filtering Screen
3-Bowl
4-Fuel Inlet
5-Inlet Valve
6-Pump Chamber
7-'-Diaphragm Spring
B-Rocker Arm Spring
9-Rocker Arm
10-Rocker Arm Pin
11-Rocker Arm Link
U~u"Je~t~:nd Pull Rod
14-Fuel Outlet
15-Body Screw
When the carburetor bowl is full, the float in the
carburetor closes the needle valve, thus creating a
pressure in pump chamber. This pressure will hold
diaphragm assembly down against spring pressure
where it will remain inoperative until the car-
buretor requires more fuel and the needle valve
opens. The rocker arm spring is merely for the
purpose of keeping the rocker arm in constant
contact with the eccentric.
The diaphragms are manufactured of several layers
of specially treated cloth which is impervious to
fuel.
The fuel pumps have a large reservoir and fluctua-
tion chamber. The sediment bowls are clamped to
the pump assemblies, making it a simple matter to
clean out any sediment. Each valve assembly is a
self-contained unit made up of a valve cage, a fiber
valve and a valve spring. The valve assemblies are
held in place by a valve retainer permitting easy
and speedy removal of the assemblies.
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