EGSA System Troubleshooting and Maintenance 2 — Questions and Answers
Question 1: A generator set shows high coolant temperature alarms shortly after startup. After ruling out a low coolant level, what is the next most likely cause to investigate?
- Faulty coolant temperature sensor
- Clogged radiator fins or restricted airflow (Correct answer)
- Incorrect fuel-to-air ratio
- Low oil pressure
Correct answer: Clogged radiator fins or restricted airflow
Clogged radiator fins or restricted airflow are common causes of overheating once low coolant level has been ruled out.
Question 2: When performing a load bank test on a standby generator, what parameter is used to verify the unit can sustain rated output?
- No-load frequency stability
- Voltage regulation under full rated kW load (Correct answer)
- Idle speed RPM
- Battery charge current
Correct answer: Voltage regulation under full rated kW load
Voltage regulation under full rated kW load confirms the generator can sustain its nameplate output without excessive voltage drop.
Question 3: A diesel engine cranks but will not start. Fuel pressure is confirmed adequate. Which component failure could prevent fuel injection from occurring?
- Faulty radiator cap
- Defective fuel injection solenoid or ECM (Correct answer)
- Worn alternator brushes
- Low coolant temperature
Correct answer: Defective fuel injection solenoid or ECM
A defective fuel injection solenoid or ECM can prevent fuel from being injected even when supply pressure is adequate.
Question 4: What is the purpose of an automatic voltage regulator (AVR) self-test function found on modern generator control panels?
- To calibrate the fuel governor
- To verify the AVR can maintain voltage within specified limits under simulated conditions (Correct answer)
- To test the battery charger output
- To reset the maintenance timer
Correct answer: To verify the AVR can maintain voltage within specified limits under simulated conditions
The AVR self-test verifies that voltage regulation circuits function correctly within specified limits before a live load event.
Question 5: A generator producing voltage but tripping on overcurrent when connected to a known good load most likely has which problem?
- Undersized circuit breaker or a misconfigured overcurrent relay setpoint (Correct answer)
- Defective coolant thermostat
- Low engine oil level
- Incorrect air filter restriction
Correct answer: Undersized circuit breaker or a misconfigured overcurrent relay setpoint
An undersized breaker or misconfigured overcurrent relay will trip prematurely when the load is within the generator's rated capacity.
Question 6: During preventive maintenance, technicians measure insulation resistance on generator windings. What minimum IR value in megohms is typically considered acceptable for a low-voltage generator?
- 0.1 MΩ
- 1 MΩ (Correct answer)
- 10 MΩ
- 100 MΩ
Correct answer: 1 MΩ
A minimum of 1 MΩ is the general industry-accepted threshold for low-voltage generator winding insulation resistance.
Question 7: What condition does wet stacking in a diesel generator indicate, and how is it typically corrected?
- Overloading; reduce load below rated kW
- Unburned fuel accumulation in the exhaust due to chronic light loading; corrected by running the engine at 75–100% load (Correct answer)
- Coolant contamination of oil; corrected by flushing the cooling system
- High ambient temperature operation; corrected by adding supplemental cooling
Correct answer: Unburned fuel accumulation in the exhaust due to chronic light loading; corrected by running the engine at 75–100% load
Wet stacking results from unburned fuel accumulating in the exhaust when a diesel runs at insufficient load, and is resolved by load banking to 75–100% capacity.
EGSA System Troubleshooting and Maintenance 2
A generator set shows high coolant temperature alarms shortly after startup.
After ruling out a low coolant level, what is the next most likely cause to investigate?