Engine Equipment
If the engine coolant overheats, the temperature-
sensing valve will open and permit the oil in the
protective system to flow to the engine crankcase.
The resulting decrease in oil pressure will actuate the
shutdown mechanism and stop the engine. Also if the
engine loses its coolant, the copper plug will be heated
up by the hot exhaust gases passing over it and cause
the temperature-sensing valve to open and actuate the
shutdown mechanism.
Whenever the engine speed exceeds the overspeed
governor setting, the oil in the line flows to the sump,
resulting in a decrease in oil pressure. The oil pressure
bellows then releases the latch and permits the air
shut-off valve to close.
When an engine is stopped by the action of the
shutdown system, the engine cannot be started again
until the particular device which actuated the
Fig. 3 - Automatic Mechanical Shutdown
shutdown mechanism has returned to its normal
System Mounting
position. The abnormal condition which caused the
engine to stop must be corrected before attempting to
The overspeed governor (Fig. 4), used on certain
start it again.
applications, consists of a valve actuated by a set of
spring-loaded weights. Engine oil is supplied to the
valve through a connection in the oil line between the
bellows and the temperature-sensing valve. An outlet
Adjustment
in the governor valve is connected to the engine oil
The only adjustments necessary in the mechanical
sump. Whenever the engine speed exceeds the
shutdown system are the low oil pressure setting of the
overspeed governor setting, the valve (actuated by the
bellows and the overspeed setting of the overspeed
governor weights) is moved from its seat and permits
governor or overspeed valve assembly. Replace the
the oil to flow to the engine sump. This decreases the
t e m p e r a t u r e sensing valve when operation is
oil pressure to the bellows, thus actuating the shutdown
unsatisfactory.
mechanism and stopping the engine.
To adjust the low oil pressure setting of the bellows,
A restricted fitting, which will permit a drop in oil
start. and run the engine until the normal operating
pressure great enough to actuate the shutdown
temperature (160-185 F or 71-85C) has been
mechanism, is required in the oil line between the
reached and the oil pressure has stabilized. Then
cylinder block oil gallery and the shutdown sensing
reduce the engine speed slowly until the bellows
devices.
disengages the latch on the air shut off valve and stops
the engine. Note the oil pressure at which the shut
down occurred. The oil pressure at disengagement
Operation
should be 5-10 psi (35-69 kPa) at 450-600 rpm; 10-
15 psi (69-103 kPa) at 601-1400 rpm; or 15-20 psi
To start an engine equipped with a mechanical
(103-138 kPa) at 1401 and above rpm. If adjustment is
shutdown system, first manually open the air shut-off
necessary, loosen the lock nut on the bellows and turn
valve and then press the engine starting switch. As
the adjusting screw clockwise to increase the oil
soon as the engine starts, the starting switch may be
pressure setting or counterclockwise to decrease the
released, but the air shut-off valve must be held in the
setting. Hold the adjusting screw and tighten the lock
open position until the engine oil pressure increases
nut when the proper setting has been obtained.
sufficiently to permit the bellows to retain the latch in
the open position.
NOTE: Set the bellows disengagement pressure
as near as possible to the high end of the
pressure range for the low engine speed
During operation, if the engine oil pressure drops
specified for the engine. For an engine
below the setting of the pressure sensitive bellows, the
equipped with a dual speed governor, set the
spring within the bellows will release the latch and
permit the air shut-off valve to close, thus stopping the
bellows disengagement at the lower setting of
the engine governor.
engine.
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