CRANKCASE BREATHER
.
MDJA
Prior
to
Spec
R
The crankcase breather is located
in
the left rear
corner
of
the crankcase and maintains
a
partial
vacuum in the crankcase during engine operation. Its
purpose is to ventilate the crankcase and control oil
loss.
It
consists of a metal filter packed
into
the tube
on the crankcase, a rubber cap with flapper valve, and
a
hose connecting it to the engine air horn.
To
disassemble, remove the rubber cap from the
crankcasetubeand prythevalveoutofthecap. Wash
the valve in fuel at regular intervals and, if defective,
replace
it.
At
the same time, pull the baffle out of the
breather tube and clean
it.
Install the valve with the
perforated disk toward the engine. Figure
81
shows
the crankcase breather.
BREATHER TUBE
FIGURE
81.
CRANKCASE BREATHER
PULSATION DAMPER
MDJC
Begin
Spec
S
and
MDJF
These enginesareequipped with a pulsation damper
which serves two major functions.
It
dampens pulsa-
tions which originate in the intake manifold and
which contribute to oil carry-over.
It
also acts as an oil
separatorto condense oil vapor and small oil droplets
(in the blowby fumes) to prevent them from getting
into the intake manifold and combustion chamber.
OVERFLOW
HOSE
OIL
DRAIN
FIGURE
82
PULSATION DAMPER
OIL
PRESSURE GAUGE
Some engines have an oil pressure gauge. If faulty,
replace
it.
Remove with a wrench and install
a
new
gauge. Check for a plugged oil passage.
The nonadjustable oil pressure switch controls the
decompression solenoid
in
the starting system,
allowing it to energize only when the switch closes.
This allows theengine
to
build upspeed, during start-
ing, before compression occurs. The switch closes at
about
5
psi
(35
kPa) under increasing oil pressure.
This is not a lowoilpressure profec-
.
fion swlfch.
If
will not profecf the
engine against slowly decreasing oil pressure.
On
MDJA
engines
if
the decompression switch does not energize,
check switch operation. Short the switch to ground when the
engine has built
up
speed during starting. The governor solenoid
should energize immediately and the engine should
start.
When fhe engine starts, check im-
mediafely for oil pressure. Shuf fhe
engine down iiollpressure does nof build up within a
few seconds. in this case, the lack
of
oil pressure
is
causing iaulfy operation, not fhe swifch.
65
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