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5.13
Section 5
Fuel System and Governor
5
Governor Control Unit (GCU) senses engine speed by
pulse voltage inputs from the ignition modules. The
GCU regulates the engine speed by variable input
voltage from a customer-supplied potentiometer or a
single pole, single throw (SPST) switch.
Potentiometer Specifications:
Adjustment Procedure
The DLA must be in the fully retracted position during
assembly. The full range of throttle plate movement will
not be achieved if the DLA is partially extended when
assembled. Loosen the two DLA mounting plate
screws located on the top of the actuator plate. With
the throttle linkage centered in the U-Clip at the end of
the DLA shaft, slide the DLA bracket assembly back
until the throttle plate is fully open. Torque the
mounting plate screws to 2.5 N·m (22 in. lb.).
Troubleshooting Procedure
Engine starts, but will not continue to run
1. Check the linkage connection between the DLA
and throttle plate.
2. Verify the DLA initializes when power is supplied
(key switch in the start or run position).
3. Test the potentiometer wiper output voltage (if
equipped).
4. Test the SPST switch (if equipped).
5. Check the wire harness and connections.
Engine does not run at the expected speed
1. Check to see that the throttle linkage and DLA
have full range of motion having no mechanical
interference.
2. Test the potentiometer wiper voltage (if equipped).
3. Test the SPST switch (if equipped).
1860 low speed endpoint
variable speed endpoint
3600 high speed endpoint
Wiper Voltage
0-1
1-9
9-16
Engine Speed (RPM)
1860 low speed endpoint
3600 high speed endpoint
Engine Speed (RPM)
Switch Position
Open
Closed
SPST Switch Specifications:
GCU Safety Features
In the event of an engine overspeed condition, the
GCU will shut down the engine by grounding the
ignition modules.
The GCU will shut down the engine by grounding the
ignition when power to the GCU is lost.
Linkage
The throttle linkage spring will fully open the throttle
plate if the linkage becomes detached from the DLA.
This will create an overspeed condition causing the
engine to shut down. The DLA shaft will have to be
manually screwed back into the body, and then
retracted before reassembling the linkage.