SHUTOFF AND ALARM SYSTEMS
(WITH OIL PRESSURE DELAY OR FUEL PRESSURE SWITCH)
1. Rack 2. Oil pressure (time delay) or fuel pressure switch. 4. Magnetic pickup. s Diode assembly. 6. Starter. 7.
The engine speed is felt by magnetic pickup (4). As
the teeth of the flywheel go through the magnetic lines of
force around the pickup, an AC voltage is made. Dual
speed switch (3) measures engine speed from the
frequency of this AC voltage.
Rack solenoid (I) is connected to the fuel rack by
linkage. When it is activated, it will move to stop the flow
of fuel to the engine.
If the engine speed increases above the overspeed
setting ( i 18% of rated speed) of the dual speed switch,
the overspeed switch [which is part of dual speed switch
(3)] will close across terminals DSS-7 and DSS-8. This
completes the circuit to rack solenoid (I) through the now
closed pressure switch (2) and activates the solenoid to
shutdown the engine.
NOTICE To help prevent damage to the engine, find
and correct the problem that caused the engine to
overspeed, before the engine is started again.
After an overspeed shutdown, a button on the dual
speed switch must be pushed to open the overspeed
switch before the engine will run.
Diode assembly (5) is used to stop arcing, for protection
of the system.
An oil pressure (time delay) or fuel pressure switch
(2) is used to prevent discharge of battery (7) through the
solenoid when the engine is stopped. The dual speed
switch can be connected to the battery constantly
because it uses less than 20 MA of current when the
engine is stopped.