7032 SOUTH 196th - KENT, WA 98032 - (253) 872-0141 / FAX (253) 872-8710
OPERATION / MAINTENANCE MANUAL
MODEL 50 VIBRATORY HAMMER WITH MODEL 260 POWER UNIT
VII-2B. Controls: (Understanding How They Work) (Continued...)
7. Throttle "RAISE/OFF/LOWER" Switch
This switch is used to throttle the engine up or down. This switch turns a small motor hooked
to the engine throttle. APE power units with CAT engines use a system supplied by CAT. The
CAT engine throttle requires two small relays mounted inside the control panel. The APE
units with Cummins engines do not have relays and are wired directly to a Murphy worm
drive throttle box mounted on the engine.
8. "OIL PRESSURE" Gauge (CAT Engines Only Older Models)
An electric "OIL PRESSURE" Gauge is provided to monitor engine oil pressure. The CAT oil
pressure gauge is wired to an oil pressure sender that forces the gauge to read zero pressure
when the power is turned on. The CAT sender is a variable resistor that is normally grounded
and slowly decreases the grounded voltage as pressure is delivered to it. As the voltage
decreases, the pressure gauge reading increases. To test the sender, disconnect the wire
l eading to it and place one OHM meter lead on the sender terminal and the other lead on the
engine. It should shown maximum resistance. If not, replace it. (CAT ONLY Older Models.)
9. "ENGINE OIL PRESSURE" Gauge (CUMMINS Engines)
The engine oil pressure gauge on the Cummins engine is wired to a variable resistor that goes
from zero resistance when not pressurized to full resistance when at maximum pressure.
When the power switch is turned on the gauge reads zero. When the engine is started the
engine oil pressure increases and the variable resistor begins to ground out as engine oil
pressure pushes on it. If the gauge continues to read zero, the sender may be faulty. To test
the sender, disconnect the wire from the pressure gauge and place one lead of the OHM
meter on the sender terminal and the other lead on the engine. OHM meter should read
zero resistance. If OHM meter shows resistance then replace it.
10. "ENGINE OIL PRESSURE" Switch
A small ENGINE OIL PRESSURE Switch mounted on the diesel engine is designed to ground
out when pressure drops below 40 psi. The switch is designed to be normally open when
under pressure. When pressure is lost, the switch closes sending a grounded signal that
activates the safety shut down switch on the panel which cuts power to the fuel solenoid and
shuts down the engine.
11. "WATER TEMPERATURE" Gauge
An electric "WATER TEMPERATURE" Gauge is provided to monitor engine water
temperature.
VII. MODEL 260 POWER UNIT (Continued...)
Page 7-6
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