Chevrolet 1977 light duty truck Service Manual page 19

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B-9 UNDERBODY—Corrosive material used for ice and
snow removal and dust control can accumulate
on the underbody. If allowed to remain, these
materials can result in accelerated rusting and
deterioration of underbody components such as
fuel lines, frame and floor pan, exhaust system,
etc. At least once each year, preferably after a
winter's exposure, these corrosive materials
should be removed by flushing the underbody
with plain water. Particular attention should be
given to cleaning out those areas where mud
and other foreign materials collect.
SECTION C—EMISSION CONTROL MAINTENANCE
L-6 ENGINE
NOTE: Additional recommended maintenance
instructions relating to vehicle use, evidence of
maintenance, and service replacement parts are
included in the New Car Warranty Information
folder.
C-1 CARBURETOR CHOKE AND HOSES-Check choke
mechanism and vacuum break for proper oper­
ation. Any binding condition which may have
developed due to petroleum gum formation on
the choke shaft or from damage should be cor­
rected. Check carburetor choke hoses for
proper connection, cracking, abrasion or deteri­
oration and correct or replace as necessary.
Check operation at 6 months or 7,500 miles, 24
months or 30,000 miles and every 12 months or
15,000 miles thereafter.
C-2 THERMOSTATICALLY CONTROLLED AIR CLEANER -
Inspect installation to make certain that all hoses
and ducts are connected and correctly installed.
Also check valve for proper operation.
C-3 ENGINE IDLE SPEED - Adjust engine idle speed
accurately (following the specifications shown
on the label under the hood). Adjustments must
be made with test equipment known to be
accurate.
C-4 EARLY FUEL EVAPORATION (EFE) SYSTEM-Check
valve for proper operation. A binding condition
must be corrected. Check thermal vacuum
switch for proper operation. Check hoses for
cracking, abrasion or deterioration. Replace
parts as necessary.
C-5 CARBURETOR MOUNTING— At designated intervals
torque carburetor attaching bolts and/or nuts
to compensate for compression of the gasket.
C-6 VACUUM ADVANCE SYSTEM AND HOSES-Check
system for proper operation and hoses for
proper connection, cracking, abrasion or deteri­
oration. Replace parts as necessary.
C-7 FUEL FILTER—Replace filter in carburetor at des­
ignated intervals or more frequently if clogged.
C-8 POSITIVE CRANKCASE VENTILATION SYSTEM (PCV)
—Check the PCV system for satisfactory oper­
ation at 15,000-mile intervals, and clean filter.
Replace the PCV valve at 30,000-mile intervals
and blow out PCV valve hose with compressed
air. Replace deteriorated hoses.
The PCV filter (located in the air cleaner) should
be replaced whenever the air cleaner element
is replaced.
C-9 SPARK PLUG WIRES— Clean exterior of wires; re­
move any evidence of corrosion on end termi­
nals. Inspect spark plug wires for evidence of
checking, burning, or cracking of exterior insu­
lation and tight fit at distributor cap and spark
plugs or other deterioration. If corrosion cannot
be removed or other conditions above are noted,
replace wire.
C-10 IDLE STOP SOLENOID—Check for proper operation.
An inoperative solenoid must be replaced.
C-11 SPARK PLUGS—Replace plugs at designated in­
tervals with type specified in Owner's and
Driver's Manual.
C-12 TIMING AND DISTRIBUTOR CAP - Adjust ignition
timing following the specifications shown on
label under the hood. Also, carefully inspect the
interior and exterior of the distributor cap and
rotor for cracks, carbon tracking and terminal
corrosion. Clean or replace as necessary.
C-13 AIR CLEANER ELEMENT— Replace the engine air
cleaner element at designated intervals. The
PCV filter should be replaced at the same inter­
val. Operation of vehicle in dusty areas will
necessitate more frequent replacement. Your
dealer can be of assistance in determining the
proper replacement frequency for the condi­
tions under which you operate your vehicle.
CAUTION: Do not operate the engine without
the air cleaner unless temporary removal is
necessary during repair or maintenance of the
vehicle. When the air cleaner is removed, back­
firing can cause fire in the engine compartment.
C-14 EVAPORATOR CONTROL SYSTEM (ECS)-Check all
fuel and vapor lines and hoses for proper con­
nections and correct routing as well as condi­
tion. Remove canister and check for cracks or
damage. Replace damagedordeteriorated parts
as necessary. Replace filter in lower section of
canister.
C-15 FUEL CAP, FUEL LINES AND FUEL TANK -
1. Inspect the fuel tank, cap and lines for dam­
age which could cause leaks.
2. Remove fuel cap and inspect gasket for an
even imprint from the filler neck, and any indi­
cations of physical damage.
3. Replace any damaged or deteriorated parts.
SECTION C — EMISSION CONTROL MAINTENANCE
V-8 ENGINE
NOTE: Additional recommended maintenance
instructions relating to vehicle use, evidence of
maintenance, and service replacement parts are
included in the New Vehicle Warranty Informa­
tion folder.
C-1 THERMOSTATICALLY CONTROLLED AIR CLEANER -
Inspect installation to make certain that all
hoses and ducts are connected and correctly in­
stalled. Also check valve for proper operation.
C-2 CARBURETOR CHOKE AND HOSES - Check choke
mechanism and vacuum break for proper oper­
ation. Any binding condition which may have de­
veloped due to petroleum gum formation on
the choke shaft or from damage should be
corrected. Check carburetor choke hoses for
proper connection, cracking, abrasion or deteri­
oration and correct or replace as necessary.
C-3 ENGINE IDLE SPEED - Adjust engine idle speed
accurately (following the specifications shown
on the label under the hood). Adjustments must
be made with test equipment known to be accu­
rate.
C-4 EARLY FUEL EVAPORATION (EFE) SYSTEM-Check
valve for proper operation. A binding condition
must be corrected. Check thermal vacuum
switch for proper operation. Check hoses for
cracking, abrasion or deterioration. Replace
parts as necessary.
C-5 CARBURETOR MOUNTING— At designated intervals,