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1-6
GROUP
1-
ENGINE AND EXHAUST SYSTEM
uum
is high. The high
vacuum over
comes
the tension
of
the
spring
pres
sure
and
seats
the
valve
(Fig.
11).
With
the
valve
in
this
position,
all
the
ventilating
air
passes
through
a
calibrated
orifice
in
the
valve.
With
the
valve
seated, there
is
minimum
ventilation.
As
engine speed
increases
and manifold vacuum
decreases,
the
spring forces
the
valve
off
its
seat
and
to
the
full
open
position.
This
increases
the
flow
of
ventilating
air.
COOLING SYSTEM
The
coolant
is
drawn
from
the
bottom
of
the
radiator
by
the
water
pump
which
delivers
the
coolant
to
the
cylinder
block (Fig. 12).
The
coolant
travels through
cored
passages
to
cool
the
entire
length
of
each
cylinder
wall.
Upon reaching
the
rear
of
the
cylinder
block,
the
coolant
is directed
upward
into
the
cylinder
heads
where
it
cools
the
combustion
chambers,
valves,
and
valve seats on
its
return
to the
front
of
the
engine.
The
coolant
from
each
cylinder
head flows
through
the
water
pas
sages
in
the
intake
manifold
and
past
the
water
thermostat, if it is
open,
into
the
radiator
supply
tank.
If
the thermostat
is
closed,
a
small
TO
RADIATOR
SUPPLY TANK
FIG.
12
Cooling
System
portion of
the
coolant
is
returned
to
the
water
pump
for
recirculation.
A1249-B
The
entire
system
is
pressurized
to
12-15
psi.
ENGINE TROUBLE DIAGNOSIS
Engine
performance
complaints
usually fall
under
one
of
the
basic
headings
listed
in
the
"Engine
Trouble
Diagnosis
Guide."
When
a
particular
trouble
can not
be
traced
to
a
definite
cause
by
a simple
check,
the
possible
items
that
could
be
at
fault
are
listed in
the
order of
their
probable occurrence.
Check
the
items
in
the
order
listed.
For
example,
under
"Poor
Acceleration,"
the
igni
tion
system
is listed
as
a
probable
cause of
the trouble.
All
the
ignition
system
items
that
affect acceleration
are
listed.
Check
all
these
items
before proceeding
to the
next proba
ble
cause.
ENGINE
TROUBLE
DIAGNOSIS
GUIDE
ENGINE
WILL
NOT CRANK
The
cause of
this trouble
is
usually
starter.
If
the
engine
cranks,
it
indi-
in
the
starting
system
(Part
9-2).
cates
that
water
is
leaking
into
the
If
the
starting
system
is
not at
fault,
cylinders.
Remove
the
cylinder
check
for
a
hydrostatic lock
or
a
head(s)
and
inspect
the
gaskets(s)
seized engine as
follows:
and/ or
head(s)
for
cracks.
Examine
Remove
the
spark
plugs, then
at-
the
cylinder
block for
cracks.
tempt to
crank
the
engine
with
the
ENGINE
CRANKS
NORMALLY,
BUT WILL
NOT START
Check
the
fuel
supply.
If
there
is
to
be
checked.
Hold
the
adapter
ap-
sufficient
fuel in
the
tank,
the
cause
proximately
3/ie
inch from
the
exhaust
of
the trouble
probably
lies in
either
manifold
and
crank
the
engine.
the
ignition
or
the
fuel
system.
To determine
which
system
is
at
if
THERE
IS
NO SPARK OR
fault,
perform
the
following
test:
A WEAK
SPARK AT
THE
Disconnect
a
spark
plug
wire.
SPARK
PLUGS
Check
the
spark
intensity
at
the
end
of
the
wire
by installing
a
terminal
The
cause of
the trouble
is in
the
adapter
in
the terminal
of
the
wire
ignition
system.
CONTINUED ON
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