MDE Unit 14 start systems Quiz

MDE 14 Q1

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Question 4:

What role does the hydraulic accumulator play in the hydraulic oil start system of a diesel engine?

C) It maintains hydraulic pressure for starting the engine

A) It stores excess hydraulic fluid for future use

D) It filters impurities from the hydraulic oil

B) It regulates the fuel supply to the engine

Correct Answer: C) It maintains hydraulic pressure for starting the engine
Explanation: The hydraulic accumulator stores hydraulic pressure and releases it when needed to engage the starting mechanism, ensuring that sufficient pressure is available for engine start-up.

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Question 3:

Which interlock is commonly found in a diesel engine hydraulic oil start system to ensure safe operation?

D) Fuel pressure regulator

A) Engine oil pressure switch

C) Coolant temperature gauge

B) Hydraulic fluid level sensor

Correct Answer: B) Hydraulic fluid level sensor
Explanation: The hydraulic fluid level sensor is an interlock that ensures there is sufficient hydraulic fluid in the system to prevent damage or malfunction during the start-up process.

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Question 6:

In a hydraulic oil start system, what is the purpose of the hydraulic control valve?

C) To monitor the temperature of the hydraulic oil

B) To filter impurities from the hydraulic fluid

D) To provide additional cooling to the hydraulic system

A) To regulate the flow of hydraulic fluid to the starting motor

Correct Answer: A) To regulate the flow of hydraulic fluid to the starting motor
Explanation: The hydraulic control valve regulates the flow of hydraulic fluid to the starting motor, controlling the engagement and operation of the engine start mechanism.

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Question 5:

Which safety interlock prevents the hydraulic oil start system from operating if certain conditions are not met?

B) Battery voltage sensor

D) Starting motor relay

C) Engine temperature sensor

A) Hydraulic pressure switch

Correct Answer: A) Hydraulic pressure switch
Explanation: The hydraulic pressure switch is a safety interlock that ensures the hydraulic oil start system only operates if there is adequate hydraulic pressure, preventing damage or improper start-up.

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Question 2:

Which of the following components is typically included in a diesel engine hydraulic oil start system?

A) Hydraulic pump

D) Turbocharger

B) Fuel filter

C) Air compressor

Correct Answer: A) Hydraulic pump
Explanation: The hydraulic pump is a key component in the hydraulic oil start system, providing the necessary hydraulic pressure to engage the starting mechanism.

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Question 1:

What is the primary function of the hydraulic oil start system in a diesel engine?

D) To enhance the lubrication of engine components

C) To initiate the engine’s start-up by engaging the starting mechanism

A) To assist with fuel injection timing

B) To provide additional cooling to the engine

Correct Answer: C) To initiate the engine’s start-up by engaging the starting mechanism
Explanation: The hydraulic oil start system is primarily used to engage the starting mechanism of the diesel engine, helping to initiate the engine’s start-up.

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MDE 14 Q2

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Question 2:

Which component of the electric starting system provides the electrical power needed to turn the starter motor?

A) Alternator

D) Voltage regulator

C) Battery

B) Starter motor

Correct Answer: C) Battery
Explanation: The battery provides the electrical power needed to turn the starter motor, enabling the engine to crank and start.

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Question 1:

What is the primary function of the solenoid in a solenoid-operated, battery-powered electric starting system?

B) To engage the starter motor with the engine’s flywheel

C) To monitor the engine’s oil pressure

D) To cool the battery during operation

A) To regulate the fuel flow to the engine

Correct Answer: B) To engage the starter motor with the engine’s flywheel
Explanation: The solenoid’s primary function is to engage the starter motor with the engine’s flywheel, enabling the starter motor to crank the engine.

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Question 3:

How is the solenoid activated in a solenoid-operated starting system?

B) By an electronic control unit (ECU)

D) By a current flowing through its coil

C) By a push-button on the dashboard

A) By a mechanical switch

Correct Answer: D) By a current flowing through its coil
Explanation: The solenoid is activated by a current flowing through its coil, which creates a magnetic field that moves the solenoid plunger to engage the starter motor.

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Question 5:

What happens when the starter switch is turned on in a solenoid-operated starting system?

D) The fuel pump is deactivated

B) The solenoid engages the starter motor and the engine cranks

C) The alternator charges the battery

A) The battery is disconnected from the starter motor

Correct Answer: B) The solenoid engages the starter motor and the engine cranks
Explanation: Turning the starter switch sends current to the solenoid, which engages the starter motor and causes the engine to crank.

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Question 7:

What is the purpose of the starter relay in an electric starting system?

B) To supply power to the ignition system

C) To amplify the current to the starter motor

A) To engage the solenoid

D) To monitor the engine temperature

Correct Answer: C) To amplify the current to the starter motor
Explanation: The starter relay amplifies the current from the battery to the starter motor, enabling it to provide the high torque needed to crank the engine.

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Question 6:

Which component prevents the starter motor from operating when the engine is already running?

D) Starter inhibitor switch

B) Ignition switch

C) Neutral safety switch

A) Starter relay

Correct Answer: D) Starter inhibitor switch
Explanation: The starter inhibitor switch prevents the starter motor from operating if the engine is already running or if the transmission is not in the correct position, ensuring safe operation.

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Question 4:

Which of the following describes the role of the starter motor in the electric starting system?

B) To provide cooling to the engine

A) To generate electrical power for the ignition system

C) To crank the engine and initiate combustion

D) To regulate the engine’s fuel injection

Correct Answer: C) To crank the engine and initiate combustion
Explanation: The starter motor cranks the engine, turning the flywheel and initiating the combustion process necessary for engine start-up.

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MDE 14 Q3

1 / 9

Question 1:
Which of the following is a safety device commonly fitted to the air starting system of a large medium-speed marine diesel engine?

C) Fuel oil purifier

A) Pressure relief valve

B) Exhaust gas temperature sensor

D) Governor actuator

Correct Answer: A) Pressure relief valve
Explanation: The pressure relief valve is a critical safety device in the air start system to prevent over-pressurization, which could lead to system failure or damage.

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Question 5: Which of the following could cause a failure to start in a large marine diesel engine due to an issue with the air starting system?

D. Excessive crankcase pressure.

B. Incorrect fuel injection timing.

A. Air start valve stuck in the open position.

C. Low engine coolant level.

Correct Answer: A. Air start valve stuck in the open position.

Explanation: If the air start valve is stuck in the open position, it can prevent the correct buildup and release of pressure needed to start the engine. This issue directly affects the air starting system and can lead to a failure to start. Other options like incorrect fuel injection timing or low engine coolant level, while important, do not directly impact the air starting process.

Correct Answer: A. Air start valve stuck in the open position.

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Question 3:
In an air starting system, the interlock system is designed to:

B) Maintain constant air pressure in the starting air system

A) Ensure that the engine cannot be started unless the turning gear is disengaged

D) Monitor the lube oil temperature during engine start-up

C) Regulate the amount of fuel injected during startup

Correct Answer: A) Ensure that the engine cannot be started unless the turning gear is disengaged
Explanation: The interlock system prevents the engine from starting while the turning gear is engaged, which could otherwise lead to severe mechanical damage.

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Question 2: If an engine does not start when initiating the start sequence, and the air start lever is in the correct position, what should be the next step?

B. Inspect the turbocharger for blockages.

D. Check the engine cooling water temperature.

A. Check for leaks in the starting air system.

C. Verify the correct positioning of the camshaft.

Correct Answer: A. Check for leaks in the starting air system.

Explanation: After confirming that the air start lever is in the correct position, the next logical step is to check for leaks in the starting air system. Leaks can cause a drop in pressure, preventing sufficient air from reaching the cylinders to start the engine. This is a critical issue to address before considering other potential problems.

Correct Answer: A. Check for leaks in the starting air system.

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Question 4:
Which safety device in the air starting system is responsible for releasing excess air to the atmosphere in case of an overpressure condition?

A) Safety valve

C) Starting air valve

B) Air distributor

D) Crankcase relief valve

Correct Answer: A) Safety valve
Explanation: The safety valve releases excess air to the atmosphere when the pressure in the air start system exceeds a set limit, protecting the system from potential damage.

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Question 1: When initiating the start sequence on a large medium-speed marine diesel engine with individual air starting valves, the engine fails to start. Which of the following is the first check you should perform?

A. Check the air start valve timing.

B. Check if the main starting air receiver is pressurized.

D. Check the lube oil level in the sump.

C. Check the condition of the fuel injectors.

Correct Answer: B. Check if the main starting air receiver is pressurized.

Explanation: If the engine fails to start, the first thing to check is whether the main starting air receiver has enough pressure to deliver the required air for starting. Without sufficient pressure, the starting system won't function correctly, and the engine will not start. This is a fundamental step before checking more complex components like timing or fuel injectors.

Correct Answer: B. Check if the main starting air receiver is pressurized.

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Question 2:
What is the primary function of the non-return valve in the air starting system of a medium-speed marine diesel engine?

A) To prevent backflow of air into the receiver

D) To control the flow of cooling water

B) To regulate the fuel injection timing

C) To measure exhaust gas temperature

Correct Answer: A) To prevent backflow of air into the receiver
Explanation: The non-return valve ensures that compressed air does not flow back into the air receiver, which is crucial for maintaining system safety and efficiency.

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Question 3: During an attempt to start a large marine diesel engine, you find that no air is being delivered to the cylinders. What could be a likely cause?

B. Exhaust valve stuck in the open position.

D. Low cylinder compression.

A. Faulty fuel pump.

C. Closed starting air supply valve.

Correct Answer: C. Closed starting air supply valve.

Explanation: If no air is being delivered to the cylinders, one of the most likely causes is that the starting air supply valve is closed. This valve must be open to allow pressurized air to flow into the cylinders during the start sequence. Other issues like a faulty fuel pump or exhaust valve problems would not directly cause a lack of air delivery.

Correct Answer: C. Closed starting air supply valve.

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Question 4: What should be inspected if there is air leakage during the start sequence of a marine diesel engine?

B. Starting air valve condition.

A. Fuel injection timing.

C. Piston ring clearance.

D. Turbocharger speed.

Correct Answer: B. Starting air valve condition.

Explanation: Air leakage during the start sequence often indicates a problem with the starting air valve, such as improper seating or wear. The condition of the starting air valve should be inspected to ensure it is functioning correctly and sealing properly to prevent leaks.

Correct Answer: B. Starting air valve condition.

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MDE 14 Q4

1 / 8

Question 3:
Which interlock prevents a medium-speed diesel engine from being started if the engine's crankcase doors are open?

C) Exhaust valve interlock

B) Crankcase door interlock

A) Crankcase explosion relief valve interlock

D) Cooling water pressure interlock

Correct Answer: B) Crankcase door interlock
Explanation: The crankcase door interlock ensures that the engine cannot be started if any of the crankcase doors are open, preventing accidental starting during maintenance.

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Question 1:
Which of the following interlocks is most commonly fitted to a direct air start medium-speed diesel engine to prevent the engine from starting if the turning gear is engaged?

B) Turning gear engagement interlock

D) Fuel injection interlock

C) Lube oil pressure interlock

A) Over-speed trip interlock

Correct Answer: B) Turning gear engagement interlock
Explanation: The turning gear engagement interlock prevents the engine from starting if the turning gear is engaged, ensuring that the engine cannot start accidentally during maintenance.

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Question 4:
What is the significance of the crank angle at which the air start valve closes on a four-stroke diesel engine?

D) It guarantees maximum compression during the power stroke

A) It ensures that the exhaust valve opens immediately

B) It prevents the backflow of exhaust gases into the starting air system

C) It allows the inlet valve to open at the right moment

Correct Answer: B) It prevents the backflow of exhaust gases into the starting air system
Explanation: The air start valve closes before the exhaust valve opens to prevent the backflow of exhaust gases into the starting air system, maintaining system integrity and safety.

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Question 3:
How does the timing of the air start valve's opening relate to the inlet and exhaust valves' operation in a four-stroke diesel engine?

C) The air start valve opens when both the inlet and exhaust valves are open

B) The air start valve opens when the inlet valve is open and the exhaust valve is closed

A) The air start valve opens when both inlet and exhaust valves are closed

D) The air start valve opens when the inlet valve is closed and the exhaust valve is open

Correct Answer: A) The air start valve opens when both inlet and exhaust valves are closed
Explanation: The air start valve opens when both the inlet and exhaust valves are closed to ensure that the compressed air effectively pushes the piston downwards without escaping through either valve.

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Question 2:
During which stroke of a four-stroke diesel engine cycle is the air start valve usually open?

D) Exhaust stroke

C) Power stroke

B) Compression stroke

A) Intake stroke

Correct Answer: B) Compression stroke
Explanation: The air start valve opens during the compression stroke, when the piston is moving upwards, to inject compressed air into the cylinder and drive the piston downwards, initiating the engine's rotation.

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Question 4:
The low lube oil pressure interlock in a direct air start medium-speed diesel engine is designed to:

C) Ensure the fuel pumps are correctly aligned

A) Prevent starting if the oil temperature is too high

D) Ensure that the governor is set to the correct speed

B) Prevent starting if lube oil pressure is below a safe threshold

Correct Answer: B) Prevent starting if lube oil pressure is below a safe threshold
Explanation: The low lube oil pressure interlock prevents the engine from starting if the lubricating oil pressure is insufficient, which could otherwise cause severe engine damage.

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Question 1:
At what approximate crank angle does the air start valve typically begin to open on a four-stroke diesel engine during the starting process?

B) 90° after TDC

A) 0° (TDC)

D) 360° (BDC)

C) 270° after TDC

Correct Answer: A) 0° (TDC)
Explanation: The air start valve typically begins to open at or near 0° crank angle (TDC) during the starting process to initiate the engine’s rotation.

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Question 2:
What is the function of the starting air interlock in a direct air start medium-speed diesel engine?

A) To prevent the engine from starting if the cooling water temperature is too low

C) To prevent starting if the main starting air valve is not fully open

D) To ensure that the crankcase doors are properly secured

B) To ensure that the fuel valves are in the open position

Correct Answer: C) To prevent starting if the main starting air valve is not fully open
Explanation: The starting air interlock prevents the engine from being started if the main starting air valve is not fully open, avoiding potential damage to the system due to improper air flow.

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MDE 14 Q5

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Question 5:
During a routine check, what should be done if moisture is found in the air motor's air supply line?

D) Lubricate the air motor components more frequently

A) Replace the entire air supply line

C) Increase the air pressure to blow out the moisture

B) Drain the moisture and inspect the air dryer or moisture separator

Correct Answer: B) Drain the moisture and inspect the air dryer or moisture separator
Explanation: Moisture in the air supply line can cause corrosion and damage to the air motor, so it should be drained, and the air dryer or moisture separator should be inspected and maintained.

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Question 3:
Why is it important to inspect the condition of the air motor’s drive gear during routine maintenance?

D) To confirm the air pressure is within the specified range

C) To verify the air motor's air intake is clear

B) To ensure the gear is properly aligned with the engine's flywheel

A) To check for signs of overheating

Correct Answer: B) To ensure the gear is properly aligned with the engine's flywheel
Explanation: Proper alignment of the air motor's drive gear with the engine's flywheel is critical for efficient power transfer and to avoid damage to both the gear and the flywheel.

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Question 1:
What is the primary purpose of regularly checking the air pressure in the air motor starting system?

A) To ensure the air motor operates at the correct speed

D) To avoid excessive wear on the engine's crankshaft

C) To prevent the air motor from overheating

B) To maintain the correct fuel-air mixture

Correct Answer: A) To ensure the air motor operates at the correct speed
Explanation: Maintaining proper air pressure is crucial for the air motor to operate at the correct speed, ensuring reliable engine starting performance.

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Question 2:
Which of the following is a key maintenance task for the air motor to prevent corrosion and ensure long-term reliability?

B) Cleaning the fuel injectors

C) Replacing the air intake filter

D) Adjusting the valve clearances

A) Lubricating the air motor components regularly

Correct Answer: A) Lubricating the air motor components regularly
Explanation: Regular lubrication of the air motor components helps prevent corrosion, reduces friction, and ensures the longevity and reliability of the system.

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Question 4:
What is a common sign that the air motor’s exhaust port needs to be inspected or cleaned?

B) Increased air pressure in the system

A) Reduced engine starting speed

C) Unusual noise from the air motor

D) Oil leaks around the air motor housing

Correct Answer: A) Reduced engine starting speed
Explanation: A clogged or dirty exhaust port can cause back pressure, leading to reduced engine starting speed, making it essential to inspect and clean the exhaust port regularly.

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