MDE 5 End of Unit Quiz

Answer: C) Leaking nozzle seals
Explanation: Leaking nozzle seals can allow fuel to continuously leak into the combustion chamber, leading to excess fuel consumption and potential engine damage.

Answer: C) By changing the position of the plunger within the pump cylinder
Explanation: In Bosch or Jerk type fuel injection pumps, the delivered quantity of fuel oil is controlled by varying the position of the plunger within the pump cylinder. This adjustment changes the volume of fuel drawn into the pump and subsequently delivered to the injector, thereby controlling the amount of fuel injected into the engine.

Answer: A) By using a pressure relief valve to divert excess fuel
Explanation: In scroll type fuel injection pumps, a pressure relief valve is used to divert excess fuel if the high-pressure pipe fails. This valve prevents fuel from spraying out by redirecting it, thus protecting the system and maintaining safety in the event of a pipe failure.

Answer: A) Increased engine knocking and reduced power output
Explanation: Retarded fuel injection, where the fuel is injected later in the engine cycle, can lead to increased engine knocking and reduced power output. This is because the combustion process starts later, potentially causing incomplete combustion and higher pressure in the cylinder, which can result in knocking and decreased performance.

Answer: C) By modifying the position of the scroll or cam mechanism
Explanation: In scroll type fuel injection pumps, the delivered quantity of fuel is varied by modifying the position of the scroll or cam mechanism. This adjustment changes the volume of fuel that is pumped and delivered to the injector, allowing for control over the fuel quantity injected into the engine.

Answer: A) Scroll mechanism, camshaft, delivery valve, and pump housing
Explanation: The main components of a scroll type fuel pump include the scroll mechanism (which moves the fuel), the camshaft (which drives the scroll mechanism), the delivery valve (which controls fuel delivery), and the pump housing (which encloses the pump components). These parts work together to ensure efficient fuel delivery and operation.

Answer: C) By varying the displacement of the scroll mechanism
Explanation: In a scroll type fuel pump, fuel metering for high and low loads is achieved by varying the displacement of the scroll mechanism. This adjustment changes the volume of fuel pumped, allowing the pump to deliver the appropriate amount of fuel for different engine loads and operating conditions.

Answer: A) Clogged nozzle orifices
Explanation: Clogged nozzle orifices can lead to poor atomization of the fuel, resulting in incomplete combustion, reduced engine performance, and increased exhaust smoke.

Answer: A) The depth to which fuel droplets penetrate into the combustion chamber
Explanation: In diesel engine fuel injection, "penetration" refers to the depth to which the fuel droplets travel into the combustion chamber. Effective penetration ensures that the fuel reaches the areas where it can mix thoroughly with air for optimal combustion.

Answer: A) Clogged nozzle orifices
Explanation: Clogged nozzle orifices can affect the performance of the fuel nozzle by disrupting the spray pattern and reducing the efficiency of fuel injection, which can lead to poor engine performance and increased emissions.

Answer: B) It increases the spray pattern's spread and improves atomization
Explanation: High fuel pressure improves the atomization of the fuel by forcing it through the nozzle more forcefully, which increases the spray pattern’s spread and enhances mixing with air for better combustion.

Answer: B) The process of breaking down fuel into fine droplets for efficient mixing with air
Explanation: Atomization refers to the process of breaking down the fuel into fine droplets, which allows for better mixing with air in the combustion chamber. This enhances combustion efficiency and overall engine performance.