SHUTOFF AND ALARM SYSTEMS
WATER TEMPERATURE, OIL PRESSURE AND
ELECTRONIC OVERSPEED SHUTOFF WITH
TIME DELAY RELAY (Fuel Shutoff Solenoid
Energized to Run)
1. Magnetic pickup. 2. Dual speed switch. 3. Over-speed switch (N.C.). 4. Cranking speed switch (N.O.). 5. Water
temperature switch. 6. Oil pressure switch. 7. Time delay relay. 8. Switch (N.C.). 9. Fuel shutoff solenoid.
The engine speed is felt by magnetic pickup (1).
As the teeth of the flywheel go through the magnetic
lines of force around the pickup, an AC voltage is made.
Dual speed switch (2) determines engine speed from the
frequency of the voltage.
Time delay relay (7) controls the operation of fuel shutoff
solenoid (9). To prevent the engine from restarting, the
time delay relay turns off the current to the fuel shutoff
solenoid for approximately 70 seconds after the engine
When the electrical current is turned on to the time delay
relay terminal four, the current then goes to terminals six
and eleven of the dual speed switch
and to terminal one of oil pressure switch (6). Current
also flows to terminal six of the time delay relay and
through N.C. switch (8) to energize fuel shutoff solenoid
(9) so the engine will start.
When the engine starts, N.O. switch (4) in the cranking
circuit of the dual speed switch closes at a speed just
above cranking speed. This completes the circuit to
terminal two of the time delay relay. In approximately 9
seconds N.C. switch (8) in the time delay relay will open
and break the circuit between the fuel shutoff solenoid
and terminal six of the time delay relay. If engine oil
pressure has not closed oil pressure switch (6) by 9
seconds, N.C. switch (8) will