Best 10 Tips on How to Maintain Diesel Engine Governors

How to Maintain Diesel Engine Governors

Diesel engine governors are a vital part of any marine diesel engine and need to be maintained properly in order to ensure reliable operation. Proper maintenance of these components will help to extend the life of your marine diesel engine and ensure that it operates at peak efficiency. In this article, we will discuss how to properly maintain your Diesel Engine Governors, including the different types available and the best practices for each type. We’ll also discuss common issues that may arise with these components and how they can be addressed. By following these tips, you can rest assured that your marine diesel engine governor is well maintained for optimal performance.

What is Engine Governor

Diesel Engine Governors

A governor is a device that automatically maintains the rotary speed of an engine or other prime mover within reasonably close limits, regardless of the load. It controls the speed of engines, pumps, compressors, and other machinery. The primary purpose of a governor is to maintain a uniform rate over varying loads and changing conditions. Modern governors use electronic sensors and sophisticated algorithms to ensure that the machine runs steadily and efficiently.

Types of Engine Governor

  • Hydraulic type
  • Mechanical type
  • Inertia type
  • Electronic type

Governor Characterstic

  • A droop speed governor with over speed device is installed on the diesel generators.
  • A constant speed Governor with over speed tripping function is installed on the main Engines. The importance of over-speed trip fitted in the main engine is for the following important factors.
  • A sudden increase in speed and sudden change of load. This type of condition might arrive due to a loss of propeller in the rough sea.
  • Over speed, a trip is provided to safeguard against the damage of parts.
  • Over speed, the trip is attached to the camshaft through gear arrangements.
  • Over speed, the trip device cuts off the supply in the event of speed rising above 10 to 15% above the rated speed.
  • Manually reset is required before the re-start of the engine.

Use of Hydraulic Servo Engine Governor

Hydraulic Engine Governor is used for the following purpose.

  • Sensitivity
  • Isochronous.
  • Have the more high power to operate the fuel control mechanism.

Hunting of Engine Governor

Hunting is the result of abnormal increase or decrease of speed due to control of fuel supply. Hunting is caused due to the unavoidable time lag between the governor movement and response of the engine.

Engine Governor Droop

  • Governor droop is the difference between the no load speed and full load speed in percentage.
  • Small droop will result in frequent swinging.
  • Large droop setting will result in slow response of Governor.

Governor Isochronous type

  • Constant speed governor are known as Isochronous Governor.
  • Isochronous Governor has the ability to maintain the speed with zero hunting.
  • Isochronous type Governor has proportional and reset properties.

Method of Generator Engine Over speed trip test

  1. Slowly raise speed of Engine by speed adjusting knob at idle condition.
  2. The mechanism of Over speed device, should cut off the fuel supply above 15% of the engine normal speed.

Purpose of using the Speed Droop Governor in generator Engine

  1. For the load sharing ability

2.Governor should function as per the function of AVR of Alternator

Advantage of over speed trip in addition to the Governor

  1. Speed is controlled within prescribed limits by the governor.
  2. Rise of speed more than 15 % of the rated speed in the event of an accidental change in load from full load to no load.
  3. Parts may damage in the event of sudden over-speed due to the time delay action of Governor Control.
  4. For the above reasons the Over speed trip is provided.
Operation of Isochronous Governor
  1. Isochronous Governor maintains the constant speed without hunting.
  2. Isochronous Governor has the temporary speed droop.
Sensitivity of a Engine Governor

 Is the ability of a governor to control the speed in narrow limits?

Maintenance schedules on Engine Governor
  1. Periodically check of Oil
  2. Change of Governor oil
  3. Greasing of linkages and joints

Governor function in details (Engine Governor)

Diesel Engine Governors
Diesel Engine Governors

The amount of fuel is required to be controlled for an engine operating under changing loads and speed range.This device is called the governor. 

Factors affecting the Diesel Engine speed.. (Engine Governor)

  1. Injected fuel amount in to the cylinders.
  2. Engine working load. 

Assuming the engine is operating at a certain speed. The Engine slows down upon the increase in load. Engine will speed up due to the fuel injection while the decrease of load. Engine speed at a specific range can be kept by regulating the fuel injection amount. Various types of governor has been desigined to do this.

Operating principle of the Governor is centrifugal force. Due to the centrifugal force an object rotating in a circular path will have the tendency of keeping away from its rotating axis. Forces due to the increase in speed will affect the rotating weights. Vital centrifugal force pushes the weights from their axis.

   The speed governor prevents Engines from speeding or racing. Over speed governor is based on pair of flyweights fitted on the governor drive shaft. Flyweight’s outward motion is conveyed to a collar. Which slides on the shaft? Fuel pump linkage is actuated with the movement of this collar. A spring presses upward against the collar.

Collar is pressed upward by the spring. Flyweight has the tendency to move upward during the operation of the engine at average speed. Movement is retarded by the spring. As soon as the engine speed rises above the safe speed, the centrifugal for ce of the flyweight depresses the spring. This decreases the Engine speed by reducing the amount of fuel injected.

Over speeding of the engine is prevented by the over speed governor.

 In some engines over speed governor is also named as over speed trip, prevents the engine from over speeding if the speed exceeds the limit.P rinciple of One flyweight over speed working is centrifugal force.The rotating flyweight is held closely to the driveshaft by a spring, during the engine operation at safe speed. Flyweights trip a latch by moving outward during the over speeding of Engine. Engine will stop shutting off the fuel to the injection vavle by the movement of fly weights.

Consider repeating the action in steps. A spring holds the flyweight to the drive shaft. Centrifugal force controls the resistance of spring during the engine speeding up, and the flyweights fly out away from the drive shaft.  Spring loaded plunger is released due to the flyweights tripping the latch. Engine stops due to fuel cut out lever bringing the  fuel control of the fuel pumps to no fuel position.

Reset the latch and fuel pumps before restarting the engine.This is done by this reset arm which is mounted on the reset lever shaft. 

Stopping the engine manually (by hand) is done with the help of  the cut-off cam mounted on the engine. Cam turns the cut-out lever and shuts off the fuel pumps when the Engine’s starting lever is moved to stop.

 The regulating Engine Governor not only keeps the Engine from over speeding but maintains the engine speed at a fixed rate despite changes in load. In this governor, the flyweights are linked hydraulically to the fuel control assembly. A piston connected to the fuel system controls a housing spring is part of this assembly. Oil pressure on the lower side of the piston balances the downward pressure of the spring. The amount of oil in this space is regulated by a valve called the pilot valve controlled by the flyweights. 

During the operation of engine at set speed, pilot valve plunger covers the port to power cylinder. The plunger is held in this position by the fly weights .if the engine load decreases however the engine speeds up and the additional centrifugal force throws the fly weights outward raising the pilot valve plunger.

Thus the pilot valve plunger uncovers the port and oil from the power cylinder flows to drain passage through pilot valve cylinder. The power spring forces the piston down actuated the linkage to the fuel system controls and the supply of fuel to the engine cylinders is diminished.

As the engine speed returns to the set rate the flyweights resume their original position and the pilot valve plunger again covers the port. The flyweights move inward if the load decreases. Inward movement of flyweights causes to lower the pilot valve plunger allowing the oil to flow the pilot valve chamber to the power cylinder.

This oil supplied by a pump is under a pressure sufficiently high to overcome the pressure of the power spring. The upward movement the power piston increases the amount of fuel injected. Once again as the speed returns to the set rate the flyweights resume their central position.

Governor shaft transmits the drive to the gear pump for the supply of high pressure into the system. Gear pump takes the suction from the governor sump. Return of excess oil to sump is affected by the spring loaded accumulator which maintains the stable head.

To increase the regulating governor’s sensitivity and to prevent overcorrection a compensating mechanism is used. Compensation mechanism enables the pilot valve port to keep in open for the suitable period for the engine speed to return back to pre-adjusted speed.

 A compensating plunger on the power piston shaft moves in a cylinder which is also filled with oil. When the engine speed increases and the power piston moves downward the compensating plunger is also carried down drawing oil from a cylinder below the pilot valve bushing. This creates suction above the receiving compensating plunger which is part of the bushing. The bushing moves upward closing the port to the power piston. Hence the power piston in stop conditions to disable the overcorrection.

As the flyweights and pilot valve returned to their central position Oil flowing through a needle valve allows the compensating spring to return the pilot valve bushing to its central position. Bushing and Plunger should come down at the similar speed for closing the port. Therefore adjust the needle valve to ensure the pass of oil at the suitable rate for the particular engine.

The actuating compensating plunger moves upward with the power piston during the reduction of speed below its nominal set range. This increases the oil pressure above the receiving compensating plunger. The compensating plunger travels down along with the pilot valve bushing.

 As before the port leading to the power cylinder is closed. the excess oil in the compensating system now drains out through the needle valve as the spring returns the bushing to its central position. By changing the tension of the speed adjusting spring the speed of the engine is set.

Oil allowed to leak past the various plungers for lubrication purposes is drained into the governor oil sump .these are the basic elements of this type of regulating governor In actual operation.

We shall review the functioning of the governor and maintain the engine speed under the sudden increase of load. Drop of engine speed takes place and the pilot valve plunger is lowered by the inward movement of fly weights.

 Oil from the gear pump and the accumulator forces the power piston upward increasing the amount of fuel injected into the engine cylinders. in the meantime the pilot valve bushing has moved downward closing the port in the pilot valve. As the engine speed returns to normal the fly weights and the pilot valve plunger and bushing returned to their central position .now if the load suddenly decreases and the engine start to race the fly weights move outward lifting the pilot valve plunger.

The decreasing of injected fuel amount is affected by the movement of the power piston due to the oil drain from the power cylinder. In the meantime, the pilot valve bushing has moved upward closing the port in the pilot valve. Flyweights, plunger, and bushing resume their original position upon the normalization of engine speed. Always keep the governor clean and keep it free from dirty lubricating oil.

Flush it out every two weeks with clean fuel oil. Flush it out every six months with carbon tetrachloride. Refill it with lubricating oil of the viscosity specified by the operator’s manual. Be sure that the oil is always at the proper level keeping it above five-eighths of an inch in the gauge glass never. Never tamper with the governor unless you are positive that there is some trouble with it and even then all repairs should be made only by experienced personal.

Famous brands of Governors

Woodward Governors for Engines

Diesel Engine Governors
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Woodward hydraulic-mechanical governors provide reliable and precise control of engine speed and output in virtually every type of engine application. Woodward governors are used in power generation, marine, pump, compression, and vehicle applications. Available in work output ratings from 10.8 in-lbs up to 500 ft-lbs.

These governors control Engine speed by sensing turbine rotor speed via their input drive shaft, comparing this speed to an internal speed set point, then using a rotary output terminal shaft connected to the turbine’s governor valve to control Engine inlet fuel flow. The basic principle of working of governor is that the governor spring and flyweights are so selected that at any designed engine speed centrifugal force and spring force are in equilibrium



Regulateour Europa  is the world-class governor for the control and monitoring solutions. These Governors are used for Mechanical and electronics Governors and control systems for marine, traction, industrial and offshore applications.

FAQ on Diesel Engine Governors

A diesel engine alternator governor is sometimes called a diesel engine governor.

The purpose of the governor is to control fuel to the engine cylinders in order to control the speed of the unit.

The basic principle of governor operation is that the governor springs and flyweights are chosen to balance centrifugal and spring forces at any rated engine speed.

Mechanical governors use flyweights to generate a force based on crankshaft speed, which is balanced by the governor’s spring force.

Blog Conclusion

A diesel engine governor is an essential device for any power plant that runs on diesel. It is designed to automatically maintain the rotary speed of an engine or other prime mover within close limits, regardless of changes in load and fuel consumption. This device ensures that diesel engines run efficiently, produce consistent power, and are reliable over time.

Additionally, it helps reduce maintenance costs associated with excessive wear caused by fluctuating speeds. With a dedicated and accurate diesel engine governor, businesses can benefit from improved performance and longer-term savings.

We hope you enjoyed our blog post on Diesel Engine Governors. Whether you are an expert or just a casual reader, we hope that you found this article to be informative and helpful. Please send us any questions or thoughts you have about Diesel Engine Governors in the comments section of our blog. We would love to hear from you! Thank you for reading, we are always excited when one of our posts is able to provide useful information on a topic like this!

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