DESCRIPTION
The limiting and rebalancing type PGR governor, Fig. 12-1, is used on the turbocharged engine. An electro-hydraulic speed control maintains the engine speed selected by the engine operator. The governor is provided with a sensor assembly, sensitive to abso-lute air pressure, which operates to adjust the engine load in proportion to the air supply, within the range of the load regulator, to ensure correct air-fuel ratio. In addition, a rocker arm and lever arrangement is provided on the governor to stop upward movement of the power piston through the action of the fuel lim-iter.
The governor incorporates an engine protective de-vice, Fig. 12-2, which shuts the engine down when actuated by low engine oil pressure, high oil tempera-ture, or as a result of the operation of the low water and crankcase pressure detector. A visual indication and an alarm is actuated in the event of an engine protection shutdown. A normal engine shutdown is obtained by actuating one of the speed solenoids with the stop button. Other auxiliary devices which are a part of the governor include the load regulator pilot valve, which controls oil to the load regulator, and the ORS solenoid which when energized raises the load regulator pilot valve to the minimum field posi-tion.

Fig. 12-3 illustrates the operation of the fuel control portion of the governor. The power piston spring acts to shut off fuel to the engine. Oil under pressure is used only to raise the power piston and increase the supply of fuel to the engine. The following paragraphs describe the sequence of events under different opera-tional conditions.

DESCRIPTION
The compensating mechanism prevents the engine from racing or hunting by arresting the movement of the power piston after it has traveled a sufficient amount to give the desired speed. The compensating mechanism includes the integral compensating receiv-ing piston, buffer piston and springs, and compensat-ing needle valve.
When the engine is started the first time or after instal-lation of a new or reconditioned governor or one that has been drained and cleaned and new oil added, the governor will require compensation adjustment. This is necessary to purge the governor oil system of trapped air

DESCRIPTION
Speed setting with the electro-hydraulic governor is accomplished in steps by energizing different combi-nations of the "A," "B," "C," and "D" solenoids, Fig. 12-4. Solenoids "A," "B," and "C" have plungers bear-ing on a triangular fulcrum plate at varying distances from a set fulcrum point. The triangular plate fulcrum bears on a lever which is connected to the speed con-trol pilot valve inside a rotating bushing. The "D" so-lenoid plunger bears on the rotating bushing through its cap and bearing.
To increase engine speed, the speeder spring must be compressed; or compression lessened to decrease speed. The speed setting piston position must be changed to satisfy these conditions. This is accom-plished by admitting or releasing governor oil above the speed setting piston. Admission or release of oil to or from the speed setting piston is controlled by the solenoids through the speed pilot valve and rotating bushing.
When a solenoid or different combinations of "A," "B," or "C" solenoids are energized, the triangular

fulcrum plate is forced down a distance depending on the solenoids energized. This causes the speed control pilot valve to go down. The regulating port in the ro-tating bushing is uncovered, permitting governor oil under pressure to force the speed setting piston down and compress the speeder spring. As the speed setting piston moves downward, the linkage raises the speed control pilot valve to again close the regulating port when the desired piston position has been reached.
Compression of the speeder spring forces the fly-weights in, allowing the governor pilot valve plunger to lower and permit oil to raise the power piston to increase fuel to the engine. Unbalanced oil pressure on the compensating land of the pilot valve plunger closes the regulating port when the power piston has been raised enough for the desired speed. When the new engine speed is reached, the flyweights will return to balance position against speeder spring pressure.
When a solenoid or a combination of "A," "B," or "C" solenoids is de-energized, the triangular fulcrum plate will rise, and the speed control pilot valve will also be moved upward. Since the pilot valve is raised, oil above the speed setting piston drains through the regu-lating port to the oil sump. The speed setting piston is raised by its spring. As the piston moves up, the con-necting linkage causes the speed control pilot valve to move down and close the regulating port when the de-sired position is reached.
Since the speed setting piston was raised, speeder spring compression is lessened. The flyweights will move outward under centrifugal force to lift the pilot valve plunger. Oil will then be released from under the power piston and it will move downward to decrease fuel supply and engine speed.
Energizing the "D" solenoid in combination with other solenoids lessens their effect on engine speed, since the "D" solenoid pushes down the rotating bushing and lowers the regulating port. When only the "D" sole-noid is energized, it opens the regulating port in the rotating bushing to sump, permitting oil above the speed setting piston to be released. The piston then raises and the piston extension lifts the shutdown bushing, causing the governor to shut off the engine fuel supply.
Note that oil enters the speed control rotating bushing through an intermittent supply port. This port is of such size as to allow the speed setting piston to move a full stroke in a specified time. Consequently speed in-crease is controlled under all conditions of operation. Time of speed decrease is controlled by a slot in the lower land.

DESCRIPTION
Engine shutdown can normally be accomplished by depressing the STOP button or placing the throttle in the STOP position. Either action will energize the "D" solenoid, Fig. 12-4. This action depresses the speed control rotating bushing so its port is below the land of the speed control pilot valve. This allows the trapped oil above the governor speeder spring piston to drain. The spring under the piston forces the speeder spring piston upward and the piston extension contacts the shutdown bushing on the shutdown rod. Raising the shutdown rod also lifts the power piston pilot valve. Oil will then be released from under the power piston, causing the power piston through the associated link-age to bring the injectors to the "no fuel" position.

CAUTION: Shutdown adjustment must be made on governor test stand, since this adjustment establishes the basis for fuel limit set-tings.
1. Operate governor at low idle speed.
2. Loosen shutdown bushing locknut, Fig. 12-7, and adjust shutdown bushing by turning the fuel limit nut until there is 0.79 mm (1/32) "clearance between the bottom of the shutdown bushing and of the speed setting piston fulcrum assembly.
3. Tighten bushing locknut.
Fig. 12-7 - Shutdown Adjustment Location
4. Turn test stand selector switch to OFF position and loosen speed setting piston stop screw lock-nut.
5. Adjust speed setting piston stop screw, Fig. 12-8, to position the speed indicator pointer at or slightly above the STOP mark on the speed scale.
6. Tighten stop screw locknut.
Fig.

DESCRIPTION
The purpose of the sensor assembly, Fig. 12-9, is to adjust the fuel limiter and pilot valve rebalancer ar-rangement in accordance with the absolute air pres-sure. The automatic positioning of these two controls is dependent upon engine air box pressure and atmos-pheric pressure.
The pressure sensor is a force-balance device consist-ing of an inlet check valve, an orifice pack restriction, a piston and cam assembly, a restoring spring, a bleed valve, an absolute pressure bellows arrangement, and a hydraulic amplifier.
Pressured oil enters the sensor through the inlet check valve, and is directed to the upper side of the sensor piston and through the orifice pack restriction to the under side of the sensor piston. The inlet check valve prevents siphoning of the oil from the limiter housing during shutdown periods.
The bleed valve regulates the rate of oil flow from the area under the sensor piston to the sump as a function of manifold air pressure. When the bleed valve by-passes a greater flow of oil from this area than is ad-mitted through the orifice pack, the sensor piston moves downward. Conversely, reducing the bypass oil flow to less than that admitted causes the sensor piston to rise. When the inflow and outflow of oil are equal, the piston remains stationary

The sensing element consists of two opposed, flexible, metallic bellows. The upper bellows is evacuated, and the lower bellows senses air box r pressure. A spacer joins the bellows at the center wnile the outer end of each bellows is restrained to prevent movement. Air box pressure acting internally on the sensing bellows produces a force causing the spacer to move towards the evacuated bellows. The evacuated bellows pro-vides an absolute reference, therefore the sensing bel-lows force is directly proportional to the absolute air box pressure. Movement of the bellows spacer is transmitted through an output strap and a bleed valve pin to the bleed valve diaphragm.
When the governor speed setting is advanced, the gov-ernor power piston moves upward supplying additional fuel. Since air box pressure lags engine acceleration, the fuel limiter cam and bellcrank initially remain sta-tionary until air box pressure rises. As the governor power piston moves upward increasing fuel, the fuel limit floating lever depresses the right end of the feed-back lever on the hydraulic amplifier. This pushes the amplifier pilot valve plunger below center, allowing pressured oil to flow into the area under the amplifier piston, causing the piston to rise. As the piston rises, it lifts the fuel limit lever. When the fuel limit lever con-tacts the fuel limit nut on the shutdown bushing it be-gins lifting the shutdown rod to recenter the governor pilot valve plunger. The upward movements of the fuel limit and feedback levers continue until the left end of the feedback lever raises far enough to recenter the amplifier pilot valve plunger and stop the flow of oil to the amplifier piston. At this point, the fuel limit lever recenters the governor pilot valve plunger, stopping the upward movement of the governor power piston. Although the governor flyweights are in an underspeed condition at this time, the power piston remains sta-tionary until air box pressure rises.
As engine speed and load increases, air box pressure begins to rise after a short time lag. The increase in air box pressure produces an increase in the sensing bel-lows force. The bellows force, causes the bleed valve diphragm to move further off its seat. This allows a greater flow of oil to the sump than is admitted through the orifice pack. Governor oil pressure acting on the upper side of the sensor piston forces the piston downward and further compresses the restoring spring. The piston continues its downward movement until the net increase in restoring spring force equals the bel-lows force. This restores the bellows and bleed valve diaphragm to their original positions. At this point, the outflow of oil is again equal to the inflow and move-ment of the piston is halted.
As the sensor piston and cam move downward in re-sponse to a rise in air box pressure, the bellcrank ro-tates in a clockwise direction. This allows the floating lever pivot point, the left end of the lever, and in turn the hydraulic amplifier pilot valve plunger to rise.
When the pilot valve plunger rises above center, the oil under the amplifier piston bleeds to sump through a drilled passage in the center of the plunger. The pas-sage in the plunger restricts the rate of oil flow to sump and decreases the rate of movement of the am-plifier piston to minimize hunting. As the amplifier piston moves downward, the left end of the fuel limit lever also moves downward. This lowers the shutdown rod which in turn lowers the governor pilot valve plunger and increases engine fuel.
The sequence of events described above occurs in a continuous and rapid sequence. Normal governor op-eration is overridden during an acceleration transient and engine fuel is scheduled as a function of air box pressure, regardless of governor speed setting. During steady state operation, air box pressure is normally greater than that at which fuel limiting occurs, and the sensor piston and cam will be positioned below the effective limiting point.

DESCRIPTION
The purpose of the fuel limiter is to prevent supplying fuel to the engine in excess of that which can be prop-erly consumed with the available air supply.
In response to a demand for fuel, the governor pilot valve is lowered to permit governor oil to raise the power piston. The power piston upon being raised will also lift the fuel limit floating lever, Fig. 12-10. If suf-ficient air is not available for proper combustion, the hydraulic amplifier piston, contacts the fuel limit lever which will raise the shutdown bushing and governor power piston pilot valve. The governor oil port to the power piston will then be closed and the upward or increase fuel movement of the power piston will be stopped.

DESCRIPTION
The governor drive assembly, Fig. 12-16, is mounted at the front of the engine on the accessory drive cover adjacent to the water pumps. The governor is mounted on the housing and driven through the 90° bevel gear drive. The serrated end of the drive shaft is mated into a drive plate on the governor drive gear in the accessory gear train. Lubrication of the gover-nor drive bearings is provided through drilled pas-sages in the drive housing.
A cover having a removable plug, is provided on the housing so that a tachometer adapter, Fig. 12-16, can be inserted in the drive shaft end. The adapter end is inserted into a reamed hole in the end of the governor drive shaft and has a friction fit.