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Keeping
compression
at its
maximum
and
equalized in
all cylinders
insures
smooth powerful
operation.
The tests in
the compression
section check
the
compression
in
each
cylinder
and tell you
the
con-
dition
of
the piston rings and
valves.
Electrical-The
electrical system
in
your
car is like
a
miniature
electrical
plant
that serves
a
city.
The
generator
and
charging
circuit
are
like
a
central power house with the
battery as an
electrical
storage
tank. From
the generator
some
of
the main feed wires go to the
distributor, which can be thought
of as
the
central switchboard
~f
the
ignition system because it intermittently
and
automatically connects
each spark
plug with the electrical
current
so that
ignition
of the
gas
in
the cylinder occurs
at
exactly
the right
time.
Other
feed wires go
to the lights, horns,
and
electrical
accessories.
The tests on the
eleGtrical
system
check
each
of
the three electrical
circuits;
the starting, the ignition,
and the
charging circuits.
Carburetion-Carburetion is the
automatic
mixing
of gasoline with
air in the proper proportions
at all
engine speeds and temperatures.
This is done by the carburetor
and
the built-in
automatic
choke.
In
the
carburetor
all
the openings through which
fuel
and air travel
are
fixed, excepting the
idling jets which
are controlled by the idling
adjusting
screws.
All other mixtures of gasoline
and
air are
auto-
matically
controlled by
metereng rods in relation
to
the needs of the
engine.
As
you
probably know, a
fuel-air
mixture
which contains
a large
proportion
of gasoline is calle'd
a
"rich"
mixture. One that contains
relatively little
gas
is called a "lean" mixture. The proper richness
or
leanness of the mixture depends not
onty
on the
speed of
the
engine,
but
also
on the temperature of the
engine.
The carburetor takes
care of the former-automatic choke takes care
of
the
latter.
The choke controls the
choking of your
engine automatically. A ther-
mostatic arrangement lets the temperature of the
air
under the hood
control
the ridmess
of
the mixture.
A
linkage ill
also
provided which
is
connected with
the carburetor throttle and
causes
the engine to
operate
in
"fast
idle"
during the
warm-up
period.
As
the
engine
warms up, richness is
decreased.
When normal
oper-
ating
temperature is reached, the
choking
mechanism
automatically
shuts
off and engine
slows
down to the proper idle speed.
The
checks
made by
your
Pontiac dealer on the
carburetion system
will show
what
adjustments,
if
any, are
needed
.
[ 421
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