EGSA Generator Set Maintenance 2 — Questions and Answers
Question 1: When performing a load bank test on a standby generator, what minimum load level is typically recommended to prevent wet stacking?
- 25% of rated capacity
- 50% of rated capacity
- 75% of rated capacity (Correct answer)
- 100% of rated capacity
Correct answer: 75% of rated capacity
Load bank testing at 75% or more of rated capacity burns off carbon deposits and unburned fuel that cause wet stacking in lightly loaded diesel engines.
Question 2: Which maintenance task is most critical before storing a generator set for an extended period of more than 6 months?
- Replacing the air filter
- Fogging the engine cylinders with preservation oil (Correct answer)
- Replacing the starter motor brushes
- Installing a new fuel injector
Correct answer: Fogging the engine cylinders with preservation oil
Fogging cylinders with preservation oil prevents rust and corrosion on cylinder walls and piston rings during long-term storage.
Question 3: A generator's voltage regulator is replaced but the output voltage still fluctuates. What is the most likely next component to inspect?
- Main circuit breaker
- Alternator brushes and slip rings (Correct answer)
- Battery charger
- Fuel pressure regulator
Correct answer: Alternator brushes and slip rings
Worn or contaminated brushes and slip rings cause irregular contact, producing voltage fluctuation even with a new AVR installed.
Question 4: What does a rising trend in crankcase pressure readings during routine maintenance indicate?
- Blocked air cleaner
- Worn piston rings or cylinder liners allowing blow-by (Correct answer)
- Low coolant level
- Clogged fuel return line
Correct answer: Worn piston rings or cylinder liners allowing blow-by
Elevated crankcase pressure indicates combustion gases are bypassing worn piston rings into the crankcase, a sign of internal engine wear.
Question 5: During a maintenance inspection, technician finds white crystalline deposits around coolant hose fittings. What does this indicate?
- Excessive antifreeze concentration
- Slow coolant leak allowing deposits to form as coolant evaporates (Correct answer)
- Normal condensation buildup
- Blocked radiator fins
Correct answer: Slow coolant leak allowing deposits to form as coolant evaporates
White crystalline deposits around fittings are a classic sign of a slow coolant leak where the liquid evaporates and leaves mineral residue behind.
Question 6: What is the recommended method for checking injector spray pattern without removing injectors from the engine?
- Ultrasonic flow meter attached to fuel rail
- Observing exhaust smoke color under controlled load conditions (Correct answer)
- Measuring fuel return flow rate
- Testing fuel pressure at the injector body
Correct answer: Observing exhaust smoke color under controlled load conditions
Exhaust smoke analysis under controlled load provides a practical field assessment of combustion quality and injector performance without disassembly.
Question 7: When replacing a flexible exhaust coupling on a generator set, what characteristic is most important when selecting the replacement part?
- Matching the original manufacturer's temperature and vibration rating (Correct answer)
- Selecting the lowest cost available part
- Using the longest available flex section for maximum movement
- Choosing stainless steel regardless of the original material
Correct answer: Matching the original manufacturer's temperature and vibration rating
The replacement coupling must meet or exceed the OEM temperature and vibration specifications to ensure safe and reliable operation.
EGSA Generator Set Maintenance 2
When performing a load bank test on a standby generator, what minimum load level is typically recommended to prevent wet stacking?