MDE 5 End of Unit Quiz

Answer: A) Nozzle tip
C) Needle valve
E) Spring
Explanation: In a cross section through the nozzle of a fuel injector, the main components typically include the nozzle tip, needle valve, and spring. The nozzle tip is where the fuel is ejected, the needle valve controls the opening and closing of the nozzle, and the spring helps maintain the correct position of the needle valve.

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 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: B) Improved power output and reduced exhaust emissions
Explanation: Advanced fuel injection, where the fuel is injected earlier in the engine cycle, can lead to improved power output and reduced exhaust emissions. This is because it allows for better mixing of fuel and air, leading to more complete combustion and enhanced engine efficiency.

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: C) To prevent backflow of fuel from the high-pressure side to the low-pressure side
Explanation: The delivery valve in scroll type fuel injection pumps prevents the backflow of fuel from the high-pressure side to the low-pressure side. This ensures that the fuel remains under pressure within the injection system, maintaining the correct amount of fuel delivered to the injector.

Answer: B) Leaking nozzle tip
Explanation: A leaking nozzle tip can cause uneven fuel delivery, leading to a rough engine idle and excessive exhaust smoke due to incomplete combustion.

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: 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: A) The nozzle tip
Explanation: The nozzle tip is responsible for controlling the spray pattern of the fuel. It ensures that the fuel is distributed in the correct manner to achieve optimal combustion.

Answer: A) Incorrect spray pattern
Explanation: An incorrect spray pattern from the injector can lead to poor fuel-air mixing, causing erratic engine operation and knocking.

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.