Engine System, Diesel
91
Service Manual – SC8000
Troubleshooting the Kubota Engine Speed Governing System
Follow these procedures if the engine will not run at operating speed (2200 RPM) or high speed (2400 RPM).
Governor – APECS 3000, manufactured by Woodward (manual # SE-4049). Additional information can be
found on their website.
To check the electrical control circuit:
1.
With key switch on, check for battery voltage at the governor control box (B+ and B-) inputs. The correct
value is 12 VDC.
2. Press the engine speed selection button (located on the operator control panel) with engine cranking/
running and test for 12 VDC at the governor speed select inputs 1 and 2. (See the ladder diagram for
speed selection voltage relationships.)
•
If 0 volts, check the continuity of the speed select input wiring from the governor to the Driver Box
(main controller).
•
If wiring check is OK, substitute a new Driver Box (main controller) and Dashboard Panel.
3.
Check the status lamp on the governor for fault codes. Reference the flash code table found on the
APECS 3000 website.
4. Test governor controller actuator output voltage at different speed selection modes (approximate value
3.9 VDC).
5. Check the continuity of the fuel control actuator wiring.
6. Test the
Fuel Solenoid Actuator
(see below) for an open circuit (the specification is 3.2 ohms).
7. With the engine cranking or running, check the governor magnetic pickup (RPM speed sensor) voltage
signal (see the table below).
8. Remove and inspect the magnetic speed pickup sensor for damage. When reinstalling, thread the sensor
in until it makes contact with the flywheel, then back it out one-half turn.
Table for APECS 3000 Governor Magnetic Pickup Sensor AC Voltage Values
Test condition
Approximate AC Voltage Value
Cranking
10-11 VAC
1300 RPM , Idle
34 VAC
2200 RPM, High Speed
44 VAC
2400 RPM, Turbo Speed
46 VAC
Approximate resistance value
Magnetic pick up sensor
2100K Ohms
