CHAPTER 4
SPEED CONTROLLING DEVICES
In the EN3 TRAMAN, you learned some basic
information about the methods and the devices that
control the output of the injection pumps and injectors.
The purpose of these devices is to ensure control of
engine operation.
This chapter contains general information about
maintenance and repair of speed controlling devices
known as governors. You should refer to the appropriate
manufacturer’s technical manuals and the maintenance
requirements (3-M) for more specific information.
Woodward Diesel Engine Speed Governors Operation
and Maintenance Manual, NAVSHIPS 341-5017,
Marquette Governor Maintenance Manual,
NAVSHIPS 341-5505, and Naval Ships’ Technical
Manual, Chapter 233, “Diesel Engines,” are good
sources of information.
GOVERNORS
To control an engine means to keep it running at a
desired speed, either with, or regardless of, the changes
in the load carried by the engine. The degree of control
required depends on the following factors:
l The engine’s performance characteristics
l The type of load it drives
In diesel engines, the speed and power output is
determined by varying the amount of fuel injected into
the cylinders to control combustion. Hydraulic and
mechanical are the two principal types of governors.
HYDRAULIC GOVERNORS
This chapter will deal only with the most common
troubles that may be encountered with hydraulic
governors. Poor regulation of speed may be due to the
faulty adjustment of the governor or to the faulty action
of an engine. Or it could be a problem with a
synchronizing motor, a voltage regulator, or any piece
of equipment that has a direct bearing on the operation
of the engine.
Manufacturers stated that 50 percent of all governor
troubles are caused by dirty oil. For this reason, you
should take every precaution to prevent the oil from
becoming contaminated. Most hydraulic governors use
the same type of oil that is used in the engine crankcase,
provided it is absolutely clean and does not foam. You
should change the oil in the governor at regular intervals,
depending upon the type of operation. But regardless of
the operation or the preventive maintenance schedule, it
must be changed at least every 6 months. You must make
sure the oil containers used to fill the governors are clean
and that only clean, new, or filtered oil is used. You
should also check the oil level frequently to make sure
the proper level is maintained and the oil does not foam.
Foaming oil is usually an indication that water is present
in the oil. Water in the oil will cause serious damage to
the governor.
When a new or overhauled governor is installed,
you should adjust the governor compensating needle
valve (even though it has been adjusted previously at the
factory or repair facility). This adjustment is made with
the governor controlling an engine with a load. If this
adjustment is not made, high overspeeds and low
underspeeds after load changes will result and the return
to normal speeds will be slowed. Follow the procedure
listed in the manufacturer’s maintenance manual and the
PMS.
When a governor problem is suspected, before
performing any maintenance or adjustments, disconnect
the governor fuel rod end from the fuel control rack and
make sure there is no binding or sticking of the fuel
control rack. This procedure will determine if the trouble
is actually the governor.
The chart in table 4-1 lists some of the probable
causes of problems that are common to most hydraulic
governors. This chart is for your general information,
and it should not be used as a guide to troubleshoot a
governor. You should use the applicable manufacturer’s
instruction manual for troubleshooting.
The following are the definitions of some terms
used in the chart:
HUNTS: Rhythmic variations of speed that can be
eliminated by blocking the fuel linkage manually. They
will reappear when returned to governor control.
SURGES: Rhythmic variations of speed of large
magnitude that can be eliminated by blocking the fuel
linkage manually. They will not reappear when returned
4-1
