Engine and Controls (cont.)
Trouble, Symptom & Condition
Test or Inspection
Corrective Action
Engine will not come “up” to
governed speed in GEN mode.
(Continued)
h. Defective control unit.
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.
7.
Engine goes to overspeed
when control switch (18, Fig. 1)
is in GEN position.
a. Governed speed control
adjustment set too high
(see 2-3, Fig. 11).
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.
b. Defective linkage or
actuator.
Check governor linkage and
actuator for sticking or binding
in full-speed position. Repair as
required.
c. Defective control unit.
Replace control unit. Check unit
in accordance with Barber-
Colman operating instructions.
8.
Engine is unsteady (surges)
under load.
a. Fault in engine.
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.
b. Governor system faulty or
mis-adjusted.
Check and adjust as follows:
OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
February 28/94 Revised
Chapter 3-1
Page 15
Summary of Contents for 6921 Series
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