EGSA Generator Set Maintenance 3 — Questions and Answers
Question 1: A diesel generator set starts and runs normally but trips on high coolant temperature after 10 minutes of operation. Which maintenance action should be performed first?
- Replace the thermostat
- Flush and refill the cooling system, and check for airlock (Correct answer)
- Replace the radiator cap
- Inspect and clean the alternator
Correct answer: Flush and refill the cooling system, and check for airlock
Air trapped in the cooling system prevents proper coolant circulation and is the most common cause of rapid overheating; flushing and bleeding the system is the first diagnostic step.
Question 2: What is the primary purpose of performing a dielectric absorption test (DAR) on a generator's alternator windings?
- Measuring winding resistance
- Evaluating insulation condition and detecting moisture contamination (Correct answer)
- Checking bearing alignment
- Measuring output voltage regulation
Correct answer: Evaluating insulation condition and detecting moisture contamination
The DAR test compares insulation resistance at 30 and 60 seconds to detect moisture or contamination in winding insulation before failures occur.
Question 3: When should the maintenance interval for a generator set be shortened from the manufacturer's recommended schedule?
- When operating in extreme temperatures, high humidity, or dusty environments (Correct answer)
- When the generator is used only for emergency standby duty
- When premium fuel is used
- When the generator is less than 2 years old
Correct answer: When operating in extreme temperatures, high humidity, or dusty environments
Severe operating environments such as extreme heat, cold, dust, or humidity accelerate component wear and contamination, requiring more frequent service.
Question 4: During routine maintenance, a technician notices the engine oil has a milky grey appearance. What contamination does this indicate?
- Fuel dilution from injector leak-down
- Water or coolant contamination of the engine oil (Correct answer)
- Excessive carbon buildup
- Air ingestion into the oil system
Correct answer: Water or coolant contamination of the engine oil
A milky grey oil color is a definitive sign that water or coolant has entered the crankcase, often caused by a head gasket failure or cracked block.
Question 5: What is the correct procedure for testing a generator's automatic transfer switch (ATS) without interrupting utility power to the facility?
- Manually operate the ATS while monitoring voltage with a meter
- Use the ATS test function which starts the generator and transfers load to it before switching back (Correct answer)
- Pull the main utility fuse while personnel are on standby
- Disconnect the ATS control wiring and test the generator separately
Correct answer: Use the ATS test function which starts the generator and transfers load to it before switching back
The built-in ATS test function allows a complete transfer sequence test under generator power without actually disrupting utility supply to the facility.
Question 6: What maintenance action is required when diesel fuel stored in a day tank shows visible microbial contamination (dark slime)?
- Add extra fuel stabilizer and leave it in service
- Drain, clean, and treat the tank, then refill with fresh fuel and biocide treatment (Correct answer)
- Filter the fuel through an extra stage filter only
- Increase the fuel turnover rate by running the generator more frequently
Correct answer: Drain, clean, and treat the tank, then refill with fresh fuel and biocide treatment
Microbial growth must be physically removed by draining and cleaning the tank; biocide treatment of contaminated fuel without cleaning will not eliminate the biofilm.
Question 7: Which condition is most likely to cause a generator set to fail to start during an emergency after passing its most recent weekly exercise test?
- Slightly low oil pressure reading
- Battery sulfation due to insufficient charging current between exercise cycles (Correct answer)
- Minor coolant weepage at a hose clamp
- Engine running 5°F above normal operating temperature during exercise
Correct answer: Battery sulfation due to insufficient charging current between exercise cycles
Battery sulfation from inadequate float charging is a leading cause of unexpected start failures, as the battery may deliver enough cranking amps during short exercise tests but fail under real conditions.
EGSA Generator Set Maintenance 3
A diesel generator set starts and runs normally but trips on high coolant temperature after 10 minutes of operation.
Which maintenance action should be performed first?