Buick LeSabre 1965 Service Manual page 45

ENGINE TROUBLE DIAGNOSIS 2 - 2 3
SECTION 2-C
ENGINE TUNE-CARE AND TROUBLE DIAGNOSIS
CONTENTS OF SECTION 2-C
Paragraph
2-8
2-9
Subject Page
Paragraph Subject Page
Engine Tune-Care 2-23
Hard Starting, Improper
Performance Excessive Fuel
or Oil Consumption 2-24
2-10 Excessive Valve Noise 2-25
2-11 Engine Vibration or Noise 2-26
2-12 Cooling System Trouble
Diagnosis 2-27
2-8 ENGINE TUNE-CARE
a. Purpose of Tune-up
The purpose of an engine tune-up
is to restore power and perfor-
mance that has been lost through
wear, corrosion or deterioration
of one or more parts or units. In
the normal operation of an engine,
these changes take place gradu-
ally at a number of points so that
it is seldom advisable to attempt
an improvement in performance
by correction of one or two items
only. Time will be saved and
more lasting results will be ob-
tained by following a definite and
thorough procedure of analysis
and correction of all items affect-
ing power and performance.
Economical, trouble-free opera-
tion can better be assured if a
complete tune-up is performed
each 12,000 miles.
The parts or units which affect
power and performance may be
divided into three groups.
(1) Units affecting compression
(2) Units affecting ignition, and
(3) Units affecting carburetion.
The tune-up procedure should
cover these groups in the order
given. While the items affecting
compression and ignition may be
handled according to personal
preference, correction of items
in the carburetion group should
not be attempted until all items
affecting compression and igni-
tion have been satisfactorily
corrected.
Most of the procedures for per-
forming a complete engine tune-
up are covered separately in
other sections of this manual;
therefore, this paragraph pro-
vided an outline only with refer-
ence to o t h e r sections w h e r e
detailed information is given.
a. If compression improves con-
siderably, rings are worn.
b. If compression does not im-
prove, valves are sticking or
seating poorly.
c. If two adjacent cylinders in-
dicate low compression and in-
jecting oil does not increase com-
pression, the cause may be a head
gasket leak between the cylinders.
Engine coolant and/or oil in cyl-
inders could result from this
defect.
NOTE: Low compression pres-
sure in two adjacent cylinders
indicates a possible head gasket
leak between the two cylinders?
8. Clean, inspect, gap to .035",
and install spark plugs.
9. Inspect battery and cables.
10. If battery is in good condition
but cranking speed is low, test
cranking motor circuit. (See
Group 10).
11. Adjust fan belt (and power
steering belt if so equipped). If
difficulty is experienced in keep-
ing battery charged, check gen-
erator regulator. (See par. 10-21).
12. Inspect entire ignition system
and make indicated corrections.
13. Inspect and test fuel pump.
(See par. 3-12).
14. Check gasoline filter. (See
par. 1-6).
15. Check operation of choke
valve and check setting of choke
thermostat. (See par. 3-17 and
3-18).
16. Check adjustment of fast idle
cam and choke unloader. (See
par. 3-17 and 3-18).
17. Check throttle linkage and
dash pot adjustment.
18. Adjust carburetor idle speed
and mixture. (See par. 3-8).
19. Inspect all water hose con-
nections and tighten clamps, if
necessary.
20. Road test car for power and
overall performance.