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ENGINE TUNE-UP
TUNE-UP SEQUENCE INDEX
SUBJECT
PAGE
SUBJECT
PAGE'
Spark Plugs
-
Removal.
. .
.
.
.
. . . .
.
. .
6C-1
Compression T e s t
.
.
. . . .
.
. . . . .
.
.
.
6C- 1
Spark Plugs
-
Clean
-
T e s t
-
Install.
.
.
.
.
6C-2
Ignition System
-
Service and Repairs
. . .
.
6C-2
Battery and Battery Cables
-
Clean
and T e s t .
.
.
. . . .
.
. .
.
. .
.
. .
. . .
.
6C-2
Generator and Regulator
.
.
.
. . . .
.
.
.
. .
6C-3
Fan Belt
-
inspect
and Adjust.
.'. . . . . . .
6C-3
Manifold Heat Valve
-
Check Operation
. . .
6C-3
Check Intake Manifold Bolts
.
.
. . . .
.
. .
.
6C-3
Air Cleaner
-
Service
.
.
.
. . . .
.
.
.
.
.
.
6C-3
INTRODUCTION
Fuel Lines and Filter-Inspect and Service
. .
6C-3
Coolant Level and Hoses
-
Check.
. . . . .
.
6C-3
Crankcase Oil Level
-
Check
.
.
. . . . . .
.
6C-3
Choke Adjustment.
. . . . . .
.
. . . . . . . .
6C-4
Idle Stop Solenoid.
. . .
.
. . . . . . . . .
.
.
6C-4
Connect Tune-Up Equipment
.
.
.
.
.
.
. .
. .
6C-4
Ignition Point Dwell
.
.
. . .
.
.
.
.
.
.
.
.
.
6C-4
Ignition Timing and Advance.
. .
.
. . . . .
.
6C-4
Idle Speed and Mixture Adjustment
.
.
. . . .
6C-5
Crankcase Ventilation.
. .
.
. .
.
.
. . . .
. .
6C-5
Road T e s t .
.
.
.
. .
. .
.
. . .
.
.
.
. . .
.
. 6 C - 5
EXAMPLE 1.
Engine tune-up is diagnosis and preventative mainte-
Cyl.
1
2
3
4
5
'6
nance performed at regular intervals to restore maxi-
Press.
139
137
140
131
126
112
mum performance and economy in an engine.
80% of 140 (highest) is 112. Thus cylinder No. 6 is less
It is advisable to follow a definite and thorough
than
of No.
3. This condition,
by
prmdure
and
as suggested
1 ,
speed missing, indica@s a burned valve or broken
the sequence-index above.
piston ring.
A quality tune-up is recommended every 12 months or
12,000 miles in order to assure proper engine
EXAMPLE 2.
perfomance and complete effectiveness of exhaust
Cyl.
1
2
3
4
5
6
emission systems.
Press.
95
106
100
97
95
101
SPARK PLUG REMOVAL
80% of 106 is 85. While all cylinders are well above 85.
they are all excessively low. This indicates all
Remove any foreign matter from around spark plugs
valves or, if accompanied by oil consumption, worn
by blowing out with compressed air, then disconnect
rings
or
low crank speed.
wires and remove plugs.
COMPRESSION TEST
Test compression with engine warm, all spark plugs
removed and throttle and choke wide open. Crank
engine through at least five compression strokes to
obtain highest possible reading. No cylinder should be
less than 80% of the highest cylinder (see examples).
Excessive variation between cylinders, accompanied by
low speed missing of the cylinder or cylinders which
are low, usually indicates a valve not .properly seating,
a burned valve or broken piston ring. Low pressures,
even though uniform, may indicate worn rings. Thsi
will usually be accompanied by excessive oil consump-
tion.
If compression is subnormal, tune-up will probably not
be satisfactory.
EXAMPLE 1.
Cyl.
1
2
3
4
5
6
7
8
Press.
146
148
145
154
112
147
150
151
80% of 154 (highest) is 123. Thus cylinder No. 5 is less
than 80% of No. 4. This condition, accompanied by
low speed missing, indicates a burned valve or broken
piston ring.
Example
2
NOTE:
Low compression pressures on ram air, 400
EXAMPLE 2.
H.O.
or 428
H.O.
engines are not a valid indication of
Cyl.
1
2
3
4
5
6
7
8
engine condition. Due to the long valve overlap period
Press.
95
97
106
103
97
99
with camshafis used in these engines compression
readings (at cranking speeds) as low as 120 psi are
80% of 106 is 85. While all cylinders are well above 85,
considered normal.
they are all excessively low. This indicates all poor
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