HYDRAULIC ACTUATOR, SUMP AND FILTER REPAIR INSTRUCTIONS
Section I. HYDRAULIC ACTUATOR (CLASS I, PRECISE SETS ONLY)
The hydraulic actuator (figures 13-1 and 13-2) is part
of the generator set electro-hydraulic governing
system (para. 7-1 and 7-2) and is used to control the
speed of the generator set. An error voltage sensed
by the governor system control unit is magnetically
amplified to control the power to energize the sole-
noid of the hydraulic actuator, thus changing the
high pressure input oil into a differential pressure
across the piston.
This is accomplished by a sole-
noid controlled teeter bar within the actuator that
controls the position of the actuator piston.
A malfunction of the hydraulic throttle actuator is
usually indicated by engine shutdown or overspeed
when the START- STOP-RUN switch is transferred
from the START to the RUN position, frequency
drift observed on the frequency meters, sluggish
response to load changes, or no response to load
changes. To isolate the malfunction, proceed as
a. Check for 4-6 Vdc at test points AB and CD
(see figures 1-4 and 1-5) of electric governor control
unit (A and D are positive), with engine operating. If
voltage at either point is approximately 15 volts, the
malfunction is a result of an opening in an actuator
valve coil, or connecting circuit.
b. Check that the throttle linkage (see figure 13-1)
is not badly worn or disconnected. A worn linkage
can cause sluggish response or drifting frequency. A
disconnected or broken linkage can cause overspeed,
shutdown, or no response. Also check linkage for
binding due to dirt or distortion.
c. Check condition of hydraulic filter and the lev-
el of hydraulic oil.
Either a clogged or dirty filter
or low oil level can reduce the hydraulic pressure
required to operate the actuator.
d. Check pressure output of hydraulic actuator
by removing plugs in ports Al and A2 and inserting
0-400 psi range gages.
The pressure at each port
should be 160 + 25 psi and equal, with engine operat-
ing under governor control. Operating under manual
control, with J6 disconnected, the pressure at port
A2 should be 180 + 20 psi and approximately 50 psi
higher than the pressure at port Al.
e. Check the transducer in the actuator far free-
dom of movement. The transducer must move freely
for good response.
f. If any of the above examinations indicates that
theactuator has failed, proceed with removal, dis-
assembly and repair instructions.
13-3. Removal and Disassembly.
a. Clean all hydraulic fittings and couplings
throughly to prevent contamination of system
b. Remove drain plug on bottom of hydraulic
sump and drain and discard hydraulic oil (Refer to
Operator and Organizational Maintenance Manual for
c. Remove hydraulic actuator as illustrated in
d. Remove four bolts securing bracket to
activator and remove bracket.
Disassemble actuator as illustrated in figure
To remove connector (34) tag and unsolder all
attached to connector.
Cleaning, Inspection and Repair.
Clean all parts thoroughlv with cleaning
solvent Federal Specification-P-D-680 and dry
b. Inspect all parts for damage or defective
ball joints and linkage for excessive
actuator packing and piston for dam-
Replace all defective parts.
Reassembly and Installation.
Reassemble the hydraulic actuator as illustra-
Install set screw (37) in core assemblv (40)
Then install locknut (36). Proceed
C. When installing connector (13), locate keyway
at 12 oclock position. (See figure 13-2.)
d. When installing connector (34), locate keyway
at 6 oclock position, viewed from top of valve block
(48). (See figure 13-2.)
13-6. Actuator Valve and Piston Test.