Core Essence of Hunting: Imbalanced matching of fuel supply, speed regulation, air intake and mechanical resistance. The governor repeatedly adjusts the engine speed back and forth, resulting in visible fluctuations of rotational speed, as well as corresponding swings of voltage and frequency.
I. Faults of Speed Governing System (Accounting for 80% of Hunting Failures)
1. Units with Mechanical Governors
(1) Fatigued or Uneven Elasticity of Governor Spring
Deformed or softened springs cause out-of-sync sensitivity. Minor load variations will trigger drastic fuel adjustment and periodic oscillation.
(2) Worn, Stuck Flyweights with Excessive Clearance
Loose or rusted flyweight pins lead to sluggish opening/closing movements and asynchronous speed regulation response.
(3) Insufficient, Contaminated or Overly Viscous Governor Internal Oil
Abnormal lubrication damping eliminates buffering effect and causes periodic speed fluctuation; impurities in engine oil may jam flyweights.
(4) Stuck or Loose Fuel Control Rack and Shift Fork
Unstable push-pull resistance of the rack prevents the governor from stabilizing fuel supply.
(5) Improper Adjustment of Idle Speed Screw and High-Speed Limit Screw
Overly sensitive speed regulation within idle range triggers drastic fuel increase/decrease upon tiny disturbances.
2. Units with Electronic Speed Governors
(1) Loose Speed Sensor, Incorrect Sensor Clearance or Poor Signal Cable Contact
Fluctuating collected speed signals mislead the controller to frequently adjust fuel delivery.
(2) Stuck Actuator (Throttle Motor), Insufficient Stroke or Damaged Feedback Potentiometer
(3) Incorrect Parameter Settings of Governor Controller (Excessively High Gain & Stability Parameters)
(4) Unstable Battery Voltage
Power supply fluctuations disorder the movement of the actuator.
II. Faults of Fuel Supply System
1. Air Intake in Fuel Circuit (Most Common Issue)
Leaking fuel pipes, poorly sealed filters, defective hand fuel pumps or excessively low fuel tank level allow air to enter the high-pressure fuel circuit, leading to intermittent fuel delivery and periodic speed surges.
2. Clogged Diesel Filter or Crushed Fuel Pipe
Insufficient fuel supply cannot cope with load changes and results in repeated speed fluctuations.
3. Poor Atomization, Fuel Dripping or Seized Fuel Injectors
Uneven power output among cylinders caused by inconsistent fuel injection.
4. Worn High-Pressure Pump Plungers or Poor Sealing of Delivery Valves
Unstable fuel supply pressure leads to periodic variations in fuel delivery volume.
5. Excessive Water or Impurities in Diesel Fuel
Unstable combustion and fluctuating explosion pressure induce hunting.
III. Malfunctions of Air Intake System
1. Severely Clogged Air Filter
Insufficient air intake creates inconsistent air-fuel mixture and violent combustion fluctuations.
2. Leaking Intake Pipe or Loose Turbo Pipeline
Turbocharged units suffer unstable intake pressure and fluctuating air intake volume.
3. Turbocharger Failures (Stuck Shaft, Worn Impeller)
Volatile boost pressure causes unstable power output.
IV. Mechanical Body Failures of the Engine
1. Inconsistent Compression Pressure Across Cylinders
Leaking valves, worn piston rings or slight cylinder head gasket leakage create uneven power output per cylinder.
2. Improper Valve Clearance (Too Large or Too Small)
Restricted intake & exhaust flow destabilizes cyclic air intake volume.
3. Excessive Wear Clearance of Crankshaft, Connecting Rod and Bearings
Periodic changes in mechanical resistance disrupt steady engine speed.
4. Disordered Fuel Injection Advance Angle
Offset combustion timing generates uneven power delivery.
V. External Factors of Load & Supporting Equipment
1. Severe Fluctuation or Imbalance of Load
Intermittent impact loads or severely unbalanced three-phase loads force the unit to adjust output power frequently.
2. Stuck Generator Bearing or Rotor Scuffing
Periodic mechanical drag resistance disturbs engine speed stability.
3. Abnormal Belt Transmission Resistance or Damaged Coupling Buffer Rubber Block
Jittery power transmission feeds back to the engine and triggers hunting.
Step-by-Step Quick Troubleshooting Sequence (From Simple to Complex)
1. Inspect fuel circuit for air ingress, replace diesel filter and bleed air from fuel system
2. Clean air filter and check tightness of intake pipeline connections
3. Inspect governor oil, flyweights and fuel rack for jamming
4. Calibrate fuel injectors and test operating condition of high-pressure fuel pump
5. For electronic governor units: Inspect speed probe, wiring and controller parameters
6. Verify valve clearance and cylinder compression pressure
7. Check load status and mechanical resistance of generator