Common Causes Analysis Of Diesel Generator 'Surging' (Fluctuating Speed, Unstable, Gasping) Faults

Common Causes Analysis of Diesel Generator 'Surging' (Fluctuating Speed, Unstable, Gasping) Faults
 

The core nature of a running engine: imbalance in fuel supply, speed regulation, air intake, and mechanical resistance matching, causing the governor to repeatedly adjust the speed back and forth. This results in visible fluctuations in RPM and corresponding swings in voltage frequency.

 

Ⅰ. Governor System Faults (accounting for 80% of running engine faults)

 

1. Mechanical Governor Models

 

1. Governor spring fatigue and uneven elasticity
The spring becomes soft or deformed, sensitivity is out of balance, and even slight load changes cause large adjustments in fuel, leading to oscillations.

 

2. Wear, sticking, or excessive clearance of flyweights
Flyweight pins are loose, rusted, or stuck, causing delayed opening/closing actions and unsynchronized governor responses.
 

3. Insufficient or excessively dirty oil inside the governor / oil viscosity too high

Abnormal lubrication damping, buffer failure, resulting in periodic fluctuations; oil impurities obstruct the flyweight.

 

4. Oil quantity adjustment rack, shift fork sticking, excessive clearance

The push-pull resistance of the rack fluctuates greatly, and the governor cannot smoothly control the fuel supply.

 

5. Improper adjustment of the idle adjustment screw and high-speed limit screw

The governor in the idle range is too sensitive, causing large increases or decreases in fuel with slight disturbances.

 

2. Electronic Speed Regulation Unit

 

1. Loose speed sensor, incorrect gap, poor signal wire contact

Intermittent speed signal collection causes the controller to misjudge and frequently increase or decrease fuel.

 

2. Actuator (throttle motor) sticking, insufficient travel, feedback potentiometer damaged

 

3. Speed controller parameter setting errors (gain, stability parameters too high)

 

4. Unstable battery voltage, power supply fluctuations causing actuator action disorder

 

II. Fuel Supply System Faults

 

1. Air in the fuel line (most common)

Fuel pipe leakage, filter sealing problems, air leakage in manual fuel pump, fuel tank level too low, air enters high-pressure fuel line, fuel supply intermittent, causing periodic speed fluctuations.

 

2. Diesel filter clogging, fuel pipe collapse

Insufficient fuel flow, fuel supply cannot keep up with load changes, causing repeated fluctuations.

 

3. Injector poor atomization, dripping, sticking

Uneven injection in single/multiple cylinders, uneven cylinder work, engine torque fluctuates.

 

4. High-pressure fuel pump plunger wear, outlet valve seal poor

Unstable fuel pressure, periodic changes in fuel supply.

 

5. Diesel contains water or impurities

Unstable combustion, fluctuating explosion pressure, causing engine hunting.

 

Ⅲ. Intake System Issues

 

1. Severe air filter blockage
Insufficient air intake, the air-fuel mixture fluctuates between rich and lean, causing drastic combustion variations.

 

2. Air intake pipe leaks, turbocharger piping loose
For turbocharged models, intake pressure is unstable, and intake volume fluctuates.

 

3. Turbocharger malfunction (sticking, impeller wear)
Boost pressure fluctuates, leading to unstable power output.

Ⅳ. Engine Mechanical Body Faults

 

1. Inconsistent compression pressure across cylinders
Valve leaks, piston ring wear, minor head gasket leaks, resulting in significant differences in single-cylinder work.

 

2. Valve clearance too large/too small
Intake and exhaust are not smooth, causing unstable intake air volume.

 

3. Crankshaft, connecting rod, bearing wear with excessive clearance
Mechanical resistance changes periodically, affecting speed stability.

 

4. Incorrect fuel injection advance angle
Ignition and combustion timing shifts, leading to uneven power output.

Ⅴ. Load and Supporting External Factors

 

1. Severe and unbalanced load fluctuations
Intermittent impact loads or seriously unbalanced three-phase loads cause the unit to frequently adjust output.

 

2. Generator bearing sticking, rotor scraping
Mechanical resistance changes periodically, dragging engine speed.

 

3. Belt drive abnormal resistance, coupling buffer blocks damaged
Power transmission vibration feeds back to the engine causing hunting.

Quick troubleshooting sequence (from simple to difficult)

1. Check the fuel line for air ingress, replace the diesel filter, and bleed the air

 

2. Clean the air filter and check the sealing of the intake pipe

 

3. Check the governor oil, fly weights, and rack for sticking

 

4. Calibrate the fuel injector and check the condition of the high-pressure fuel pump

 

5. For electronic governor models: check the speed sensor, wiring, and controller parameters

 

6. Verify the valve clearance and cylinder compression pressure

 

7. Check the load and mechanical resistance of the generator