Chevrolet 70 Series 1970, Service Manual

Page: 403 / 841

53 AND 71 SERIES DIESEL ENGINES 6C-6
Figure 7—Checking Injector Rack Spring
2. Governor low speed gap closed .
3. High speed sp rin g plunger on the sea t in
the governor control housing.
4. Injector fuel control racks in the fu ll fuel
position .
NOTE: The le tte r s "R" or "L" indicate the
injector location in the right or left cylinder bank,
view ed from the re a r of the engine (fig. 2). C ylin­
ders a re numbered starting at the front of the
engine on each cylinder bank. Adjust the No. 3L
injector rack control lev er fir s t to esta b lish a
guide for adjusting the rem aining in jector rack
control le v e r s.
a. D isconnect the linkage attached to the speed
control le v e r , if not p rev io u sly done.
b. Turn the idle sp eed adjusting scr ew so that
about V2" of the sc r e w p ro jects from the lock nut.
Figure 8—Adjusting Maximum No-Load Engine Speed (Typical)
NOTE: T his adjustment low ers the tension of
the low sp eed spring so it can be com p ressed ,
while clo sin g the low sp eed gap, without bending
the fuel rod s.
c. Back out the buffer screw approxim ately
5 /8 ” and rem ove valve rocker co v ers if it has not
already been done.
d. L oosen all the inner and outer injector rack
control le v e r adjusting sc r e w s on both injector
con trol tubes. B e su re a ll the in jector rack control
le v e r s a re fr e e on the injector control tubes, and
that the injector rack control le v e r s are not bind­
ing in the in jector.
e. Move the speed control le v e r to the max­
im um speed position; hold it in that position with
light finger p r e s s u r e . Turn the inner adjusting
sc r e w on rea r No. 3L (fig. 2) injector rack control
down a s shown in figure 6, until a sligh t m ovement
of the control tube le v e r is ob served or a step-up
in effort to turn the screw d riv er is noted. This
w ill p lace re a r No. 3L (fig. 2) injector in the fu ll-
fuel position . Turn down the outer adjusting screw
until it bottom s lightly on the injector control tube.
Then alternately tighten both the inner and outer
adjusting s c r e w s.
NOTE: The above step should resu lt in p lacin g
the governor linkage and control tube assem b ly in
the sam e p o sitio n s that they w ill attain w hile the
engine is running at fu ll-lo a d .
f. To be su re of the proper rack adjustm ent,
the follow ing check should be perform ed:
(1) Hold the speed control le v e r in the max­
imum speed p osition, and p r e s s down on
the injector rack with a screw d riv er or
fin g er-tip causing the rack to rotate (fig. 7).
(2) The settin g is sufficiently tight if the rack
returns to its original position . If the rack
does not return to its origin al p osition , it
is too lo o se . To co rrect this condition,
back off the outer adjusting sc r e w sligh tly
and tighten the inner adjusting sc r e w .
(3) The settin g is too tight if, when moving the
speed control le v e r from the id le to the
maximum speed p osition , the injector rack
becom es tight b efore the speed control
le v e r reach es the end of its tra v el (stop
under the governor cover). This w ill resu lt
in a sligh t step-up in effort required to
move the speed control le v e r to its max­
imum speed position and a deflection in the
fuel rod (fuel rod deflection can be seen at
the bend). If the rack is too tight, back off
the inner adjusting screw sligh tly and
tighten the outer adjusting screw .
NOTE: A fter the number one injector rack
control le v e r is co rr ectly s e t, it m ust not be chang­
ed throughout the adjustm ent of the rem aining
in jector rack control le v e r s , sin ce it is se t to the
governor gap.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL