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10-56
idle adjustment
screw.
3.
Replace the air cleaner
.
4.
Set the ignition timing to specifi-
cation.
5.
Attach an accurate tachometer to
the
engine.
6. Run the engine until the normal
operating temperature is
reached.
7.
Adjust the idle air/fuel mixture
screws to give the best quality idle at
20 R.P .M. above the specified
speed.
8. Lean off the idle air/fuel mixture
screws an equal amount on each screw by
turning in a clockwise direction until the
engine R.P.M. drops to the specified
idle
speed
.
9. Remove the air cleaner.
10. Install the blue plastic service limiter
cap.
Use care not to turn the idle mixture
when installing the
cap.
Position
.
the cap
so that it is in the maximum counter-
clockwise position with the tab of the
limiter against the stop on the carburetor.
The idle mixture screw will then be
at the maximum allowable outward or
rich
setting.
To install the service limiter cap, use a
straight forward push with thumb pressure
or a
3/
8"
rod.
11. Replace the air cleaner and recheck
the idle speed to ensure that the mixture
screws were not accidently rotated while
fitting the limiter caps.
12.
Remove the tachometer from the
engine.
FAST IDLE
ADJUSTMENT
The fast idle adjusting screw (Fig. 21)
contacts one edge of the fast idle
cam.
The cam permits a faster engine idle
speed for smoothe.r running when the
engine is cold during choke operation. As
V1271-A
FIG.
21- Fast Idle Speed Adjustment
-
Motorcraft Model4300 4-V
the choke plate is moved through its range
of travel from the closed to the open
position, the fast idle cam pick-up lever
rotates the fast idle
cam.
Each position on
the fast idle cam permits a slower idle rpm
as engine temperature rises and choking is
reduced.
GROUP 10-
FUEL SYSTEM
Make certain the curb idle speed and
mixture
are adjusted to specification
before attempting to set the fast idle
speed.
1.
With
the
engine
operating
temperature normalized (hot), air cleaner
removed and the tachometer attached,
manually rotate the fast idle cam until the
fast idle adjusting screw rests on the
specified step on the cam.
2.
Turn the fast idle adjusting screw
inward or outward as required to obtain
the specified fast idle rpm.
ANTI-STALL DASHPOT (if fitted)
1.
With the engine idle speed and
mixture ·properly adjusted, and the engine
at normal operating temperature, loosen
the anti-stall dashpot lock nut.
2.
Hold the throttle in the closed
position and depress the plunger with a
screwdriver blade. Measure the clearance
between the throttle lever and the plunger
tip. Turn the anti-stall dashpot in a
direction
to
provide
the
specified
clearance between the tip of the plunger
and the throttle lever. Tighten the locknut
to secure the adjustment.
AUTOMATIC CHOKE
THERMOSTATIC SPRING
HOUSING ADJUSTMENT
The
automatic
choke
has
an
adjustment to control its reaction to
engine
temperature.
By loosening the
clamp screws that retain the thermostatic
spring housing to the choke
housing.
The spring housing can be turned to
alter
the
adjustment.
Refer
to
the
specifications for the proper setting.
1.
Remove the air cleaner assembly,
heater hose and mounting bracket (if so
equipped) from the carburettor.
2.
Loosen the thermostatic spring
housing clamp retaining screws. Set the
spring housing to the specified index mark
and tighten the clamp retaining
screws.
3.
If other carburettor adjustments
are not required, install the heater hose
and mounting bracket (if so equipped) and
the air cleaner assembly on thecarburettor.
ACCELERA TlNG PUMP
STROKE ADJUSTMENT
The accelerating pump stroke has
been set to help keep the exhaust emission
level of the engine within the specified
limits. The additional holes provided for
pump stroke adjustment are for adjusting
the stroke for specific engine applications.
The stroke should not be changed from
the specified setting.
If the pump stroke has been changed
from the specified setting refer to the
following
instructions
to
correct the
stroke to
specification.
~efore
adjusting
the accelerating pump stroke, measure the
height of the pump piston stem as shown
in Fig.
22.
Bend the pump control rod to
correct
the
piston
stem
height
to
specifications.
If it is necessary to correct the setting,
the pump stroke can be altered as follows
:
1.
Remove
the pump pivot pin
retainer. Remove pivot
pin.
2.
Insert the pivot pin into the
desired
hole.
3.
Install the pivot pin retainer.
Position the pump rod end into the pump
arm and install the retainer.
CHOKE PLATE PULLDOWN
AND
FAST IDLE CAM CLEARANCE
CHOKEPLATEPULLDOWN
1.
Remove the air cleaner, then
remove the choke thermostatic spring
housing from the carburettor. To remove
the thermostatic spring housing from the
carburettor installed on the engine, refer to
Thermostatic Spring Housing and Gasket
Replacement.
2.
Bend a wire gauge of 0.036-inch
diameter
at
a
90
degree
angle
approximately 1/8-inch from one
end.
3.
Block
the
throttle
about
half-open so the fast idle cam does not
contact the fast idle adjustment screw,
then insert the bent end of the wire gauge
between the lower edge of the piston slot
and the upper edge of the right-hand slot
in the choke housing (Fig.
23).
4.
Pull
the
choke
piston
lever
counterclockwise until the gauge is snug in
the piston slot. Hold the wire gauge in
place by exerting light pressure in a
rearward direction on the choke piston
lever. Check the choke plate clearance
(Pull down) between the lower edge of the
choke pia te and the wall of the air
horn.
5.
To
adjust
the
choke
plate
clearance, loosen the hex head screw (left
hand thread) on the choke plate shaft
(Fig.
23) and pry the link away from the
tapered shaft.
Use a drill gauge 0.010-inch under the
specified clearance between the lower edge
of the choke pia te and the wall of the air
horn. Hold the choke plate against the
gauge and maintain a light pressure in a
rearward direction on the choke lever.
With the choke piston snug against the
0.036-inch wire gauge and the choke plate
against the drill gauge, tighten the hex
head screw (left hand thread) on the
choke plate shaft.
The use of a 0.010-inch undersize drill
gauge is to allow for tolerances in the
linkage.
Use a drill gauge equal to the size
of the specified clearance to make a final
check.
6.
Install
the
gasket
and
thermostatic spring housing on the choke
housing.
Install the spring housing retainer
and
screws.
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