A mechanical shutoff system (if equipped) provides
protection for low oil pressure and for high water
temperature. The main components are a water
temperature sensing valve (1), a oil pressure sensing
valve (2), and a shutdown cylinder (3). Pull out the
shutdown cylinder knob (4) while you start the
engine. Hold the knob out until the engine develops
enough oil pressure. When the engine has
developed enough pressure, the knob will stay in
place. If low oil pressure or if high water temperature
is sensed, the knob will be released and the plunger
in the governor housing will hold the fuel rack in the
“FUEL OFF” position.
Oil Pressure Switches
Illustration 78 g01008923
Typical example
An oil pressure switch has wires that are connected
to the electrical system for the alarm and/or for the
shutoff. The oil pressure switch senses oil pressure
at the bearing oil gallery. If sufficient oil pressure is
not achieved after engine starting, or if the engine is
running and then loses oil pressure, the fuel shutoff
solenoid is energized to shut the engine off. No
resetting procedure is required.
Engine Step Oil Pressure
This is an adjustable engine speed setting that
protects the engine from a failure that is caused by
too little oil pressure for a specified speed range. This
option requires two different oil pressure switches.
One switch has a high pressure rating. When the
engine is running above the speed setting, the
engine must maintain oil pressure higher than the
rating of the switch. The other switch has a low
pressure rating. When the engine is running below
the speed setting, the engine must maintain oil
pressure above the rating of the switch. In an
automatic start/stop system, an automatic reset
switch is used.
Overspeed Shutoffs
Illustration 79 g00293335
(1) Magnetic pickup
(2) Flywheel housing
The magnetic pickup senses the passage of the teeth
that are on the flywheel ring gear. The Electronic
Overspeed Switch is set at 118 percent of the rated
engine speed. If the engine speed increases above
the overspeed setting, the magnetic pickup will sense
the overspeed. A signal is sent to the Electronic
Overspeed Switch. The Electronic Overspeed Switch
activates both the air shutoff solenoid (if equipped)
and the fuel shutoff solenoid.
The shutoffs must be reset before the engine will
restart. The air shutoff lever that is located at the top
of the air inlet housing must be manually reset. The
cause of the overspeed must be determined before
the engine is restarted.
Water Temperature Contactor Switch
The water temperature contactor switch is located in
the cylinder head. High water temperature closes the
switch which activates an alarm or fuel shutoff. No
resetting is required. The switch will open as the
coolant cools.
NOTICE
Coolant level must be maintained in order for the
shutoff to function, because the sensing element
must be submerged in the coolant to operate.
Coolant Loss Sensor (If Equipped)
The optional coolant loss sensor is usually mounted
near the top of the expansion tank or radiator. The
sensor monitors the coolant level.
SEBU7125-13
71
Operation Section
Engine Shutoffs and Engine Alarms
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