Electrical System Checks - Chevrolet 10 Series 1970 Service Manual

LUBRICATION 0-12
engine idle becom es too slow o r rough, the ven­
tila to r va lve should
carbu retor adjustments are made to compensate
fo r the trouble.
A ir Injection Reactor System (A .I.R .)
The A ir Injection R ea cto r system is designed to reduce
a ir pollution caused by exhaust em ission s. It is en tirely
separate fro m the P o s itiv e Crankcase V entilating system .
The A ir Injection R ea ctor system op erates by oxidizing
(or buring) the hydrocarbons and carbon monoside as
they a re expelled fro m the combustion cham ber into the
exhaust. A p o sitive displacem ent a ir pump, driven by the
engine, com p resses clean filte r e d a ir, which is d is trib ­
u t e d and injected at the exhaust port o f each cylinder.
T h is fre s h a ir m ixes with the hot exhaust gases and p r o ­
m otes further oxidation (or burning) o f both hydrocarbons
and carbon monoxide by converting som e o f them to c a r­
bon dioxide and w ater. T h is does not reduce the danger
o f inhaling carbon monoxide in confined a reas. Supple­
menting the a ir pump a special calibrated carb u retor and
distributor plus related components a re required.
The A ir Injection R eactor
A .I.R . pump d riv e b elts inspected fo r w ear and tension
e v e ry 12 months o r 12,000 m ile s, whichever occu rs firs t.
In addition, com plete effective n e ss of the system , as w ell
as full pow er and p erform an ce, depends upon engine idle
speed, ignition tim ing, and idle fuel m ixture being set
according to specification .
includes these adjustments should be p erfo rm e d p e r io d i­
c a lly to assure norm al engine efficien cy , operation and
perfo rm an ce.
Controlled Combustion System (C.C.S.)
The C ontrolled Combustion System is designed to r e ­
duce a ir pollution from exhaust em issions by im proving
combustion e fficien cy . It is en tirely separate from the
P o s itiv e Crankcase Ventilating system . T h is is done by
providin g heated a ir to the ca rb u retor which p erm its
running on lea n er m ixtures fo r im proved combustion.
O ther engine m odifications consist o f a sp ecial c a li­
brated carbu retor and distributor and related com po­
nents. Com plete e ffe ctiven ess o f the system , as w ell as
fu ll pow er and p erform an ce, depends upon engine idle
speed, ignition tim ing, and idle fuel m ixture being set
accordin g to specification . A quality tune-up which in­
cludes these adjustments should be p erfo rm ed p e r io d i­
ca lly to assure norm al engine effic ie n c y , operation and
p erfo rm an ce.
Transmission Controlled Spark (T.C.S.)
P ro c e d u re s fo r checking the operation o f this system
a re outlined in Section 6T o f this manual.
T h is is an e le c tric a lly -o p e ra te d system that elim in ates
the distribu tor vacuum spark advance in a ll forw ard
tra n sm ission gea rs (or ranges, fo r autom atics) except
high fo r a significant reduction o f hydrocarbon and carbon
m onoxide em issions. T o do this, a transm ission-m ounted
sw itch con trols a solenoid va lve which regulates mani­
fold vacuum to the distributor; during operation in the
low g e a rs (o r ran ges) the solenoid va lve reduces vacuum
supply to the d istrib u tor fo r a retard ed spark condition;
during high g ea r the solenoid valve a llow s full m anifold
vacuum to the distrib u tor fo r advanced spark. Cold start
conditions a re m et by means o f an o v e r r id e switch. When
be checked b efore any
system should have the
A quality tune-up which
the engine is cold, this w ater tem perature
sw itch circum vents norm al operation o f the system by
d ire c tly activating the solenoid va lve fo r advanced spark.
On some engines a " Hot" o v e rrid e term in al is combined
with the switch to allow vacuum advance i f engine tem ­
peratu res r is e above 232°F.
Evaporation Emission Control (E.E.C.)
T h is system is designed to reduce fuel vapor em ission
that norm ally vents to the atm osphere fro m the gasoline
tank and ca rbu retor fuel bow l. E very 12 months o r 12,000
m iles, w hichever occu rs fir s t, (m ore often under dusty
conditions), the filte r in the base o f the canister must be
replaced and the canister inspected. A ll other parts are
s e rvice d as a com plete replacem ent as outlined in S ec­
tion 8.
ENGINE TUNE-UP, EMISSION CONTROL A N D

ELECTRICAL SYSTEM CHECKS

Fuel and e le c tr ic a l system s are subject to w ear and
contamination and req u ire p eriod ic cleaning and adjust­
ments to maintain maximum econom y and perform an ce.
P r o p e r adjustment o f engine idle speed, idle fuel m ix ­
ture, ignition tim ing and operation o f the P o s itiv e Crank­
case Ventilation V alve (P C V ) are im portant to control
hydro-carbon and CO em issions within governm ent le g ­
isla ted le v e ls . These adjustments and an operational
check of the P C V V alve should be made at the fir s t o il
change (4 months or 6,000 m iles, w hichever occurs fir s t).
The above fuel and e le c tr ic a l system checks also a re in­
cluded in engine tune-ups which are recom m ended at one
y e a r o r 12,000-m ile in tervals.
M an ifo ld H eat Control V a lv e
Check m anifold heat control va lve fo r freedom o f op­
eration. If shaft is sticking, fre e it up with GM M anifold
Heat Control Solvent o r its equivalent.
Drive Belts
E v e ry 6000 m iles — Inspect d riv e b elts fo r w ear,
fra yin g, cracking, and tension. B elts which a re in poor
condition should be replaced im m ediately.
Check tension by applying m oderate thumb p ressu re
midway between pu lleys. I f the center to center distance
between pulleys is 13 to 16 inches, the belt should d eflect
1/2 inch. If the center to center distance is 7 to 10
inches, the belt should d eflect 1/4 inch.
should be retensioned to give the c o r r e c t deflection .
Electrical System
CAUTIO N: Headlamp
checked p erio d ica lly .
malfunctions be c o rre c te d prom ptly fo r safety.
Distributor
C o rr e c t distributor point gap is v e r y im portant. The
d istribu tor points a re cleaned and adjusted as p art o f a
good engine tune-up. If th eir condition is questioned,
r e le a s e the distributor cap clam ps, rem ove cap and lift
o ff ro to r. Separate the
being badly burned. Clean the points with a brea k er
point file . If the points do not clean up with a few strokes
sensitive
Loose belts
aim s h o u l d also be
It is im portant that any
points and inspect them for
CHEVROLET TRUCK SERVICE MANUAL