Maintenance of Major Components
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z
Unsatisfactory performance
If the governing system functions poorly, perform the following tests.
z
Insufficient magnetic speed sensor signal
A strong magnetic speed sensor signal will eliminate the possibility of missed or extra pulses. The
speed control unit will govern well with 0.5 volts RMS speed sensor signal. A speed sensor signal of
3 volts RMS or greater at governed speed is recommended. Measurement of the signal is made at
Terminals C and D.
The amplitude of the speed sensor signal can be raised by reducing the gap between the speed
sensor tip and the engine rind gear. The gap should not be any smaller than 0.020 in (0.45 mm).
When the engine is stopped, back the speed sensor out by 3/4 turn after touching the ring gear tooth
to achieve a satisfactory air gap.
Symptom Test Probable fault
Engine
overspeeds.
Do not crank. Apply DC
power to the governor
system.
Actuator goes to full fuel. then, disconnect speed
sensor at terminals C & D.
– If actuator still at full fuel
→
speed control unit
defective.
– If actuator at minimum fuel position
→
errorneous
speed signal.
Check speed sensor data.
Manually hold the
engine at the desired
running speed.
Measure the DC voltage
between terminals A(-) &
F(+) on the speed
control unit.
1. If the voltage reading is 4.0 to 6.0 VDC.
a) SPEED adjustment set above desired speed.
b) Defective speed control unit.
2. If the voltage reading is above 6.0 VDC.
a) Actuator or linkage binding.
3. If the voltage reading is below 4.0 VDC.
4. Gain set too low.
Actuator does not
energize fully.
Measure the voltage at
the battery while
cranking.
If the voltage is less than 15 V for a 24 V system,
replace the battery if it is weak or undersized.
Momentarily connect
terminals A and F.
The actuator should
move to the full fuel
position.
1. Actuator or battery wiring in error.
2. Actuator or linkage binding.
3. Defective actuator. See actuator troubleshooting.
4. Fuse opens. Check for short in actuator or actuator
wiring harness.
Engine remains
below desired
governed speed.
Measure the actuator
output.
Terminals A & B, while
running under governor
control.
1. If voltage measurement is within approximately 3
volts of the battery supply voltage, then fuel control
restricted from reaching full fuel position.
Possibly due to interference from the mechanical
governor, carburetor spring or linkage alignment.
2. Speed setting too low.
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