Hobart 6921 Series Operation And Maintenance Manual page 107

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
Engine and Controls (cont.)
Trouble, Symptom & Condition
Engine will not come "up" to
governed speed in GEN mode.
(Continued)
7. Engine goes to overspeed
when control switch (18, Fig. 1)
is in GEN position.
8. Engine is unsteady (surges)
under load.
February 28/94 Revised
Test or Inspection
h. Defective control unit.
a. Governed speed control
adjustment set too high
(see 2-3, Fig. 11).
b. Defective linkage or
actuator.
c. Defective control unit.
a. Fault in engine.
b. Governor system faulty or
mis-adjusted.
Corrective Action
Connect a DC voltmeter to the
leads from the control unit to the
actuator. Start the engine and
manually control speed. At
speeds below governed speed
the voltmeter should indicate
within two (2) volts of the
system voltage. If voltage is at or
near zero, turn speed adjusting
screw several turns clockwise to
be sure speed setting is not too
low because of tampering. If
voltage remains low or at zero,
replace control unit. Refer to the
Barber-Coleman Handbook for
control unit bench tests and
adjustments.
Turn speed control adjusting
screw 22 turns counterclock-
wise. Start engine. Place
control switch (18, Fig. 1) in
GEN position. If engine speed
is now well below governed
speed, turn adjusting screw
clockwise until correct speed
(2000 RPM, 400 Hz) is
reached. If engine still goes to
overspeed, proceed to step B.
Check governor linkage and
actuator for sticking or binding
in full-speed position. Repair as
required.
Replace control unit. Check unit
in accordance with Barber-
Colman operating instructions.
Before condemning the
governor system for surging,
make certain the fault is not in
the engine. Make certain all
cylinders are firing properly and
air and fuel supply is proper.
Check and adjust as follows:
Chapter 3-1
Page 15