Generator Common Faults

Powercontinuity have listed below generator common faults which are either totally avoidable or easily resolved.

Generator Common Faults

Emergency Stop pressed 

  • A generator is often located outside. Therefore, potentially accessed by many. It often happens that someone will press the emergency stop. NOTE: a generator will not start automatically when the emergency stop is not reset.

Low Fuel level

  •  A generator can happily run for hours. Also refuelled whilst running.
  • Always remember to keep an eye on the fuel tank level, especially during a prolonged power outage. You would not want to run out of fuel.

Wet Stacking

  • Running a generator continuously at low power ratings can cause wet stacking, which results in a build up of uncombusted fuel.
  • Ensuring the generator runs with a decent amount of load (either by doing an on load test or using a load bank) will avoid wet stacking.

Won’t start

  • After 3 starting attempts the generator stops and won’t start. Typically, the first place to check are the batteries. Are the terminals furred up? Or are the Lead Acid batteries over 5 years old? When batteries are old, they lose power as the chemicals degrade dramatically reducing their energy storage capability. Replace with NEW VRLA batteries with correct power rating for Diesel Generator engines.
  • Inspect the rain flap on the exhaust. The rain flap rusted down will stop the diesel generator starting. Rain flap permanently open will allow rainwater into the turbo on the engine. Check the rain flap open and closes easily. Keep well lubricated.


  • Check for loose battery terminals and if loose tighten them. Check the fluid level in the VRLA are topped up. Never allow to run dry.Generator Maintenance Daily Checks Interior common faults

Earth connection

  • Check the earthing cable is connected. Look for rust.
  • Check the earth point connection is tight.
  • Ensure the copper earth rod is firmly in the ground

Reference Voltage

  • Without an earth rod connection the generator will loose reference voltage. This will cause the generator either to stop, not start or become unstable. Every generator must have a secure fixed earth rod into the ground.
    Preferably to a depth of 1 metre.

Generator runs then stops

  • First, look at the fuel level. Should the fuel be low then the diesel generator has sucked up debris from the lower section of the fuel tank. All diesel tanks acuminate bacteria and residue at the bottom of the fuel.
  • Clean the fuel by regular fuel polishing.
  • Always keep topped up.

Generator been running for hours then stops

  • Check for low quality fuel, dirty fuel, low fuel level, blocked fuel filters.

BLACK smoke   

  • Too much fuel getting through the injections. Check the engine timing. Timing belts become slack over time and need replacing. Could be that the injections need cleaning or replacing.Black smoke is an issue.

WHITE smoke

  • Water is in the diesel fuel. Check the quality of the last fuel delivery.
  • Look at the diesel tank, is the dust cap securely tightened on the fuel fill point. White smoke is an issue.


  • Usually dirty fuel issue. Or dirty clogged fuel filters. Can also be the load on the generator is too light. For example load is 50kVA on a 500kVA generator.

Generator Overheating

  • Inspect the radiator. Is the coolant topped up? Any debris blocking the radiator veins. Is the coolant level low? Last resort is the coolant too old and become cloggy? Inspect the coolant hoses for any holes or cracks.
  • Check the oil level. Ensure the engine oil is clean and never run a diesel generator with a low oil level.
  • Check the oil filter have been replaced recently with a manufacturers approved fuel filter.generator hose checks

Voltage issues

  • Random increase and crease of voltage output from the generator. Usually associated with the AVR.
  • Check the connections.
  • Check cable condition.
  • Look for any water penetration into the AVR unit.

Generator is running but vibrating and unstable

  • Check the load being supported by the diesel generator is balanced equally across the 3 phases. Imbalanced loads will cause the diesel generator to struggle. Especially if the load is mainly on one of the phases.

Generator surging

  • Generator speeds up and then slows down randomly. Inconsistent surging. Typically a fuel blockage.
  • Check the fuel filters have been replaced with good quality filters.
  • Check the fuel level isn’t low. Look for an restrictions in the flexible fuel lines.
  • Fuel lines firmly attached to the engine block. The jubilee clips aren’t loose. Should they be loose then air can get into the fuel causing surging and hunting.


  • AVR ( Automatic Voltage Regulator ) needs attention. Check the connections. Check cable condition. Look for any water penetration into the AVR unit.

Diesel Generator completely DEAD

  • Ensure the battery charger auxiliary supply hasn’t been turned off.
  • Check the auxiliary supply to the control panel is still connected and LIVE.
  • What to do next?


For Technical help on Generator Common Faults

 contact Power Continuity engineers on 0845 055 8455


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