DETROIT DIESEL 53
Horsepower requirements on an engine may vary due to fluctuating loads; therefore, some method must be
provided to control the amount of fuel required to hold the engine speed reasonably constant during load
fluctuations. To accomplish this control, a governor is introduced in the linkage between the throttle control and
the fuel injectors.
The following type of mechanical governor used:
1. Limiting Speed Mechanical Governor.
Engines requiring a minimum and maximum speed control, together with manually controlled intermediate
speeds, are equipped with a limiting speed mechanical governor.
The governor has an identification plate located on the control housing, containing the governor
assembly number, type, idle speed range and drive ratio. The maximum engine speed, not shown on the
identification plate, is stamped on the option plate attached to the valve rocker cover.
Check Governor Operation
Governor. difficulties are usually indicated by speed variations of the engine; however, it does not necessarily
mean that all such speed fluctuations are caused by the governor. Therefore, when improper speed variations
are present, check the engine as follows:
1. Make sure the speed changes are not the result of excessive load fluctuations.
2. Check the engine to be sure that all of the cylinders are firing properly (refer to Section 15.2). If any
cylinder is not firing properly, remove the injector, test it and, if necessary, recondition it as outlined in Section
2.1 or 2.1.1.
3. Check for bind that may exist in the governor operating mechanism or in the linkage between the governor
and the injector control tube. With the fuel rod connected to the injector control tube lever, the mechanism
should be free from bind throughout the entire travel of the injector racks. If friction exists in the mechanism, it
may be located and corrected as follows:
1. If an injector rack sticks or moves too hard, it may be due to the injector hold-down clamp being too tight or
improperly positioned. To correct this condition, loosen the injector clamp, reposition it and tighten the clamp
2. An injector which is not functioning properly may have a defective plunger and bushing or a bent injector
rack. Recondition a faulty injector as outlined in Section 2.1 or 2.1.1.
3. An injector rack may bind as the result of an improperly positioned rack control lever. Loosen the rack
control lever adjusting screws. If this relieves the bind, relocate the lever on the control tube and position the
4. The injector control tube may bind in its support brackets, thus preventing free movement of the injector
racks to their no-fuel position due to tension of the return spring. This condition may be corrected by loosening
and realigning the control tube supporting brackets. If the control tube support brackets were loosened,
realigned and tightened, the injector racks must be repositioned as outlined in Section 14.
5. A bent injector control tube return spring may cause friction in the operation of the injector control tube. If
the spring has been bent or otherwise distorted, install a new spring.
6. Check for bind at the pin which connects the fuel rod to the injector control tube lever; replace the pin, if
necessary. If, after making these checks, the governor fails to control the engine properly, remove and
recondition the governor.
November, 1973 SEC. 2.7