Governor System
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GOVERNOR
These engines are equipped with an electronic governor or a mechanical governor.
ELECTRONIC GOVERNOR
Electronic Governor System
Engines with electronic governor are equipped with
either fi xed ignition timing (CH20, CH23, CH680,
CH730, certain CH740) or electronic spark advance
variable ignition timing (certain CH740). Electronic
governor components and basic function are similar, but
diagnostic and troubleshooting detail diff ers based on
which design GCU is on engine being serviced.
Electronic governor regulates engine speed at varying
loads. Typical electronic governor includes:
● Digital linear actuator (DLA).
● Throttle linkage.
● Linkage spring.
● Choke linkage.
● Throttle lever adapter.
● Governor control unit (GCU).
Components
A
B
C
D
E
F
G
A
DLA Mounting Plate
Screws
B
Digital Linear
Actuator (DLA)
C
Plastic Linkage
Retaining Clip
D Linkage Spring
E Throttle Linkage F Choke Linkage
G
Throttle Lever
Adapter
Digital Linear Actuator (DLA)
Energizing bi-directional digital linear actuator coils in
proper sequence, causes threaded shaft to move out
of, or back into rotor, in precise linear increments. When
power is removed, actuator shaft remains in position.
DLA must initialize (fully extend) to move throttle plate to
closed position, and partially open for starting. Correct
adjustment of DLA is critical to achieve full range of
throttle plate movement. See Adjustment.
Governor control unit (GCU) senses engine speed
by pulse voltage inputs from ignition modules. GCU
regulates engine speed by variable input voltage from a
customer-supplied potentiometer or a single pole, single
throw (SPST) switch.
NOTE: Actual speeds depend on application. Refer to
equipment manufacturer’s recommendations.
Potentiometer Specifi cations
Wiper Voltage Engine Speed (RPM)
0-1 Low Speed Endpoint
1-9 Variable Speed Endpoint
9-16 High Speed Endpoint
SPST Switch Specifi cations
Switch Position Engine Speed (RPM)
Open Low Speed Endpoint
Closed High Speed Endpoint
DLA Function
DLA function can be tested and confi rmed using a
stepper motor controller tool. Refer to Tools and Aids.
Testing instructions are included with this tool.
GCU Safety Features
In event of an engine overspeed condition, GCU may
shut down engine by grounding ignition modules.
GCU may shut down engine by grounding ignition when
power to GCU is lost.
Throttle Linkage
Throttle linkage spring will fully open throttle plate if
linkage becomes detached from DLA. This will create
an overspeed condition causing engine to shut down.
DLA shaft will have to be manually screwed back into
body, and then retracted before reassembling linkage, or
replace DLA and follow adjustment procedure.
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