Chevrolet 70 1969 Series, Shop Manual

Page: 295 / 913

6V-53 DIESEL ENGINE 6C-2
only one belt may be damaged or defective. Check
drive belt adjustment at all belt driven accessories.
F U E L S Y S T E M
Make periodic inspection of fuel filters, lines
and injection units for evidence of leaks and dam­
age. Repair as necessary.
Refer to applicable portion of E N G IN E F U E L
S Y S T E M (SEC. 6M) for detailed information on
fuel filters, governor control mechanism and serv­
icing fuel injectors. Recommendations pertaining
to fuel system service intervals are contained in
applicable "Owner's and Driver's Manual."
N O T E : In case of complaints of hard starting
in cold weather, refer to suggested remedies in
"Trouble Diagnosis" under "Hard Starting."
ENGINE TUNE-UP OPERATIONS
To completely tune up an engine, all major ad­
justments must be made by following the applicable
tune-up sequence given below, after the engine
has reached its normal operating temperature.
Since the adjustments are normally made while
the engine is stopped, it may be necessary to run
the engine between adjustments to prevent it from
cooling off excessively.
1. Adjust exhaust valve clearance.
2. Time fuel injectors.
3. Adjust governor gap.
4. Position injector rack control levers.
5. Adjust maximum no-load speed.
6. Adjust idle speed.
7. Adjust buffer screw.
PRELIMINARY OPERATIONS
N O T E : Before starting tune-up, perform the
preliminary procedures as described following:
C H A R G IN G CIRCUIT W IRIN G A N D
G E N E R A T O R INSPECTION
Refer to EN G IN E E L E C T R I C A L (SEC. 6Y) in
this manual for procedure required to check per­
formance of charging circuit units.
C O O L IN G S Y S T E M INSPECTION
Refer to EN GIN E C O O L IN G S Y S T E M (SEC. 6K)
in this manual for arrangement of cooling system
units and for inspection and required maintenance
procedures.
C Y L IN D E R H E A D BOLTS
Normally the cylinder head bolts should not
require retightening at tune-up intervals. When
necessary to tighten cylinder head bolts, refer to
"Cylinder Head Replacement” covered later in this
section, for bolt tightening sequence.
M A N IF O L D BOLTS
Exhaust manifold end bolts are each secured
by a lock bent against bolt heads. At tune-up inter­
val, check all manifold bolts for proper torque and
be sure end bolts are locked to prevent loosening.
F U E L S Y S T E M INSPECTION
a. Inspect all fuel lines, both the supply line
and return line between engine and fuel tank, for
evidence of leakage.
b. Referring to EN G IN E F U E L S Y S T E M (SEC.
6M) in this manual, service air cleaners and fuel
filters. Also, check operation of accelerator con­
trol linkage for free movement. Check operation of
engine stop mechanism which must function per­
fectly.
B A T T E R Y A N D B A T T E R Y C A B L E S E R V IC E
1. Using battery hydrometer, check specific
gravity of storage battery electrolyte in each cell.
Gravity reading below 1.230 (corrected to 80°F.)
indicates insufficient charge.
2. Use a voltmeter to check cranking voltage.
Be sure to place engine control in "S T O P " position
to prevent engine firing during test.
3. With voltmeter connected between solenoid
positive terminal and ground, operate starter.
Voltage of 9 volts or more when starter is crank­
ing engine indicates that battery and circuit to
solenoid are satisfactory. If voltage reading is less
than 9 volts when engine is being cranked, or if
cranking speed is low - a weak battery, defective
starter switch, or excessive resistance in starting
circuit exists.
N O T E : If, when making check of cranking volt­
age, it is noted that cranking speed is uneven, this
is an indication of uneven cylinder compression,
defective starter or starter drive.
4. In cases where loose, corroded, or other­
wise defective battery cables and/or wiring are
found, the defects must be corrected to insure
good engine performance.
5. If battery is weak or shows other evidence
of being defective, refer to appropriate coverage
in EN G IN E E L E C T R IC A L (SEC. 6Y) of this manual
for method of diagnosing battery deficiencies.
C H E C K IN G D R IV E BELTS
1. Inspect drive belts for excessive wear and
damage. If no defects are found, check belts for
proper tension.
2. When installing new drive belts or adjust­
ing old belts, use tension gauge to provide correct
tension.
C A U T IO N : Adjusting drive belts too tightly
will impose too great a load on bearings in the
driven units. Slipping will occur if drive belts are
not adjusted tight enough. Belt life will be shorten­
ed if belts are not properly tightened.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHO P MANUAL