Manitowoc Published 10-01-2012, Control # 045-08 1-21
777 SERVICE MANUAL INTRODUCTION
1
Engine Start Circuit
See Figure 1-13 for following procedures.
Since voltage to engine start switch is provided through cab
power switch and engine run/stop switch, these switches
must be closed before attempting to start the engine. When
engine start switch is activated, power is supplied to start
solenoid relay MS1. When the contacts of MS1 close,
voltage is available to starter solenoid SS that closes
contacts to the starter motor.
The primary components of the crane throttle system include
electronic fuel control (EFC) module, EFC actuator,
magnetic engine rpm transducer, foot throttle, and hand
throttle.
When throttles are moved from the off position, a regulated
voltage circuit from the throttle linear potentiometer is
complete to EFC module. The EFC module compares this
input signal to an electric signal received from engine rpm
transducer, which monitors the speed of the engine flywheel
via a magnetic pickup.
FIGURE 1-13
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