Chevrolet 1977 light duty truck, Руководство по обслуживанию

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down (econom y position), the side o f the p in stops on top
o f a flat surface on the ad ju stm en t screw located in the
cavity next to the power piston. T h e adjustm ent screw is
held from tu rn in g by a tension spring b eneath the head
o f the ad ju stm en t screw. D u rin g production flow test this
adjustm ent screw is turned up o r down which, in turn,
raises or lowers the power piston and m etering rod
assembly. This very accurately controls the fuel flow
between the rods and jets to meet emission requirements.
CAUTION:
No attempt should be made to
change the A P T adjustment. I f float bowl
replacement is required, the new bowl assembly
will include an adjustment screw pre-set by the
factory.
A n ex p a n d e r (garter) spring b eneath the plunger
cup on the accelerator p u m p assembly im proves pu m p
fuel delivery.
All M 4 M C /M 4 M E models use the bowl m ounted
choke housing with thermostatic control assembly.
The choke shaft and some other parts o f the choke
system are Teflon coated to insure smooth choke
operation.
The carburetor p a r t n u m b e r (Fig. 6C-33) is stam ped
on a vertical section o f the bowl, near the secondary
throttle lever. Refer to the part n u m b e r on the bowl
when servicing this carburetor. W h e n replacing the float
bowl assembly, follow the instructions contained in the
service package. S tam p or engrave the model n u m b e r on
the new float bowl.
The p rim a ry side o f the carb u reto r has six systems
o f operation. They are float, idle, m ain metering, power,
pum p, and choke. The secondary side has one metering
system which supplements the p rim a ry m a in metering
system and receives fuel from a com m on float chamber.
(Figs. 6C-34).
S H IF T
- Y E A R
— D A Y OF Y E A R
CARBURETOR IDENTIFICATION