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ENGINE FUEL AND EXHAUST SYSTEMS
TROUBLE DIAGNOSIS
3-7
SECTION 3-8
FUEL SYSTEM TROUBLE DIAGNOSIS
CONTENTS OF SECTION 3-8
Paragraph
SubJect
Page
3-5
Hard Starting.
.
. .
. . .
.
. . . .
. . . . .
.
3-7
3-6
Improper Engine Performance
.
.
.
.
3-8
Paragraph
SubJect
Page
3-7
Excessive Fuel Consumption
.
. . .
.
3-8
Bulletin
No.
Page No.
SERVICE BULLETIN REFERENCE
SUBJECT
3-5 HARD STARTING
a. Improper Use of Accelerator Pedal
If
the engine has been operating satisfac-
torily and developing full power when hot, hard
.
starting
may
be due to improper use of the
accelerator pedal when cranking the
engine.
See paragraph
3-4.
b. Improper Ignition
Before attempting any correction in fuel sys-
tem make certain that the battery and ignition
system are in proper condition. See paragraph
10-44.
c. Improper Vacuum Switch Timing
Hard starting may be caused by incorrect
timing of the accelerator vacuum switch.
If
the
switch is timed too early, the engine will be
cranked with insufficient throttle opening and
failure to start, or stalling after
starting,
will
result. Extremely late timing may bring the
choke
unloader
into operation and cause hard
starting with a cold
engine.
See paragraph
10-32 (Carter) or
10-33
(Stromberg).
d. Improper Adjustinent of Fast Idle Cam or
Choke Unloader
An incorr ectly adjusted fast
idle
cam
may
provide insufficien
t
throttle
opening an
d
stall-
ing will result as soon as
accelerato r
pedal
is
released.
If
the choke unloader goes into action too
soon it may cause hard starting when engine
is cold.
If
choke unloader goes into action too
late or not at all, it may cause hard starting
when engine is partially warm, hot, or flooded.
See paragraph 3-23
(Carter)
or 3-30 (Strom-
berg).
e. No Fuel at Carburetor
No fuel may be delivered to carburetor due
to empty gasoline tank or stoppages in filters,
strainers or feed
pipes,
or inoperative fuel
pump. Test fuel supply as described in para-
graph
3-17.
f. Improper Carburetor Adjustment
Improper setting of carburetor idle needle
valves may cause stalling after
starting.
A
high fuel level in float bowl will cause flooding
and consequent hard
starting.
Check fuel level
and adjust carburetor
(par. 3-12) .
g. Low Grade Gasoline
Low grade gasoline is usually insufficiently
volatile to provide easy starting in cold weather
even though it may perform reasonably well
after the engine is started and warmed up. A
change to higher grade gasoline is the only
remedy.
h. Volatile Gasoline
In some parts of the country,
gasolines
are
marketed which are very volatile
and generally
advertised
as "easy starting
gasolines." Some
of
these
fuels are so
volatile they boil (com-
monly r
eferred
t
o
as "
per colation" ) in a
car-
buretor bowl which is only normally
warm,
especially when the engine is shut off following
a run. This overloads the manifold, resulting
in an over rich mixture which may cause "de-
layed"
starting.
Such gasolines are not necessary in a Buick
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