Chevrolet 10 Series 1970 Service Manual page 373

NOTE: Vacuum and
keys to c o rre c t operation of the R ochester g o v ­
ern or. If a ll parts are fr e e to m ove as intended
and there are no vacuum leaks, the unit w ill
operate co rre c tly .
G overning system s g en era lly malfunction in one of two
ways:
1. They do not govern at a ll.
a. A vacuum leak in the units o r tubing.
b. " Spinner" unit stuck due to d irt, o il, o r some
other m a teria l depositing in the mechanism .
c. O r ific e s in the carbu retor cloggin g so no vacuum
could be developed in the governing system .
2. The system " o v e r g o vern s" : governs when it should
not, causes loss o f pow er, etc.
the vacuum passages w ere to becom e clogged with
d irt, o il, o r other fo reig n m a teria ls. A re a s m ost
lik e ly to " c lo g " are the o r ific e s in the actuator, and
the area where a ir bleeds through the distribu tor
" spinner" valve.
E ith er type o f malfunctioning
im p ro p er spinner setting; spring post out of position in
the carbu retor actuator;
actuator.
SUGGESTED PROCEDURE FOR FIN D IN G
CAUSES OF IMPROPER G O V E R N IN G
1. L o c a liz e the trouble on the veh icle. With the vacuum
tube disconnected at the distributor, run the engine at
about 3,000 rpm and place a fin g e r o v e r the end of
the tube. If there is no noticeable change in engine
operation, the trouble is probably in the actuator or
tubing. If the engine speed is noticeably affected by
this, the distribu tor " spinner" can be suspected.
2. If d istribu tor trouble is indicated p e rfo rm the fo llo w ­
ing operation (r e fe r " Ignition System, S ervicin g units
o ff the V e h ic le " in Section 6Y fo r detailed operation).
General D e s crip tio n ..............................................................................
Maintenance Procedures .....................................................................
Elem ent Replacement .....................................................................
A ir cleaners on a ll m odels operate p rim a rily to r e ­
m ove dust and d irt fro m a ir b efo re it is drawn into the
carbu retor and engine. The a ir clean er also helps to
reduce engine noise and quenches any flam e that may be
caused by engine backfire through the carburetor.
T h ree types o f a ir clean ers are used on trucks. They
a re the o il wetted paper elem ent a ir cleaner, the two
elem ent a ir cleaner and the o il bath a ir cleaner.
The o il wetted paper elem ent a ir clean er (fig . 1A) con­
sists o f an accordian pleated oiled paper filt e r supported
fr e e operation are two
This could result from :
This could result if
could be caused by:
bent o r stretched spring in
AIR CLEANERS
Page
6M-9
6M-10
6M-10
GENERAL DESCRIPTION
a. Rem ove distribu tor from engine, rem ove spinner
va lve and clean and visu ally inspect the parts and
passages fo r p ossible faults.
b. Check the seals. Do this by connecting the lo w er
vacuum connector to a vacuum pump, and " plu g­
g in g" the va lve hole in the shaft eith er with the
fin g ers o r other suitable means. Slight " seep age"
around the seals is not abnorm al; how ever, a v a c ­
uum gauge reading within 2" hg. o f the maximum
that can be
" squ eezed" should be possible if the seals are in
s a tisfa ctory condition.
s iv e ly they should be replaced.
c. When the spinner parts are
should be wiped with a rag saturated with light o il
to provid e slight, but not e x cessive lubrication.
3. If actuator o r tubing trouble is indicated:
a. Rem ove the vacuum tube at the actuator, run the
engine at about 3000 rpm and place a fin ger o v e r
the end o f the actuator. If there is no change in
engine operation, probably the actuator is at fault.
A sign ifican t change in engine rpm would indicate
tube leakage and tube should be replaced.
b. If the tubing is not defective, check the actuator
fo r leakage. With the o r ific e s " stopped up" with
the fin g ers, o r other means, no leakage should
occur. A lso check fo r p rop er seal o f diaphragm
co v e r and condition of diaphragm its e lf. Vacuum
in the g o vern or housing can be checked by r e ­
m oving the connection to the distributor and a t­
taching a vacuum line.
reading check the diaphragm fo r holes and be
sure the vacuum passage is clea r.
c. If no leakage is found, clean a ll of the component
parts.
d. If tam pering is
with the governing parts of an engine that is g o v ­
erning p ro p erly .
INDEX
Inspecting Paper E le m e n t................................................................
Cleaning Polyurethane B a n d ............................................................
Cleaning Oil Bath C lea n er................................................................
by w ire mesh with a p la stiso l seal on both top and bottom.
The two elem ent a ir cleaner (fig . 2A) consists of an o il
wetted polyurethane band wrapped around an o il wetted
paper elem ent.
The o il bath a ir clean er (fig . 3A) u tilizes an o il sump
in the a ir clean er bottom and a fib re elem ent.
On most applications o f the two elem ent a ir clea n er it
is used in conjunction with an exhaust m anifold heat stove
(fig . 4A). A ir tem perature is autom atically controlled by
a therm ostatic va lve which selects warm ed a ir fro m the
ENGINE FUEL 6M -9
obtained w i t h the vacuum hose
If the seals leak e x c e s ­
reassem bled, they
If there is no vacuum
suspected, visu ally check parts
CHEVROLET TRUCK SERVICE MANUAL
Page
6M-10
6M-10
6M-11