Chevrolet DB90 Series, Руководство по обслуживанию

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S ec. 6C -63
rpm . The variable lo w -sp eed lim iting speed gov­
ernor is s im ila r to the lim iting speed governor
with the exception of the spring housing and its
com ponents.
G overnor identification is provided by a name
plate attached to the governor housing. The le tte r s
V .L .S.L .S. stam ped on the name plate denote a
variab le lo w -sp eed lim itin g speed m echanical gov­
ernor.
OPERATION
During highway operation the governor func­
tions a s a lim itin g speed governor, controlling the
engine idling speed and lim iting the maximum o p er­
ating speed. At the unloading area , or when power
ta k e-o ff is to be used, the throttle is left in the
id le speed position and the rem ote control knob is
turned to the speed required within the above range
to operate the auxiliary equipment. The governor
then functions as a variable speed governor, m ain­
taining a constant speed when the load is contin­
uously changing during the unloading operation.
B efo re resum ing highway operation, the rem ote
control knob m ust be turned a ll the way back to
id le position .
ADJUST GOVERNOR GAP
NOTE: P erform the governor adjustment (tune-
up) a s follow s: A fter adjusting the exhaust v a lv es,
tim ing the in jecto rs, adjust the governor, position
the injector rack control le v e r s , no-load adjust­
m ent, idle and buffer sc r e w adjustment.
With the engine at operating tem perature, ad­
just the governor gap as follow s:
1. With the engine stopped, rem ove flex ib le
coupling, manual control shaft, the two attaching
b o lts and withdraw the governor high speed spring
retain er cover (fig. 3).
2. L oosen lock nut and back out the buffer
scr ew .
IMPORTANT: T he buffer sc rew m ust be ad­
justed with caution, sin c e it contacts the connect­
ing link, and turning the buffer sc rew in ca u ses
in jecto rs to go toward full fuel position.
3. Make the p relim in ary idle speed (550 rpm
minimum) adjustm ent a s follow s (fig s. 2 and 3).
a. Back out the variable lo w -sp eed adjusting
shaft until the shoulder on the shaft contacts the
shaft retain er.
b. Start the engine. Then, hold the idle adjust­
ing lock nut and lo o sen the lo w -sp eed adjusting
shaft retain er.
c . Adjust the retain er and shaft assem b ly to
obtain the d esired idle speed (550 rpm minimum).
Tighten lock nut to retain the adjustm ent. Back out
the buffer sc r e w a fter the idle speed is established,
53 AND 71 SERIES DIESEL ENGINES
Figure 2 —V ariable Low Speed Lim iting Speed M echanical
Governor Sprin g H ousing an d Com ponents (Typical)
until it extends ^approximately 5/8" from the lock
nut.
NOTE: It may be n e c e ssa r y to sligh tly adjust
the buffer screw to take the su rge or ro ll from the
engine to sta b ilize id le speed for accurate setting.
DO NOT RAISE ENGINE SPEED ABOVE IDLE
SPEED SETTING BY TURNING BUFFER SCREW
IN.
4. Stop the engine, disconnect throttle and stop
linkage, and rem ove the governor cover and le v e r
asse m b ly .
5. Clean and rem ove the valve rocker cover,
on In -lin e 6-71 S e r ie s d ie se l engine.
6. R em ove the fuel rod from the differential
le v e r and the injector control tube le v e r on In -lin e
6-71 S e r ie s d ie se l engine. This i s not n ecessa ry
on V engines.
CHEVROLET s W s 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT