MDE 5 End of Unit Quiz

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) 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: 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: 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) 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) 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: 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: 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: 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: 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: B) To inject fuel into the combustion chamber at high pressure
Explanation: The primary function of a diesel engine fuel nozzle is to inject fuel into the combustion chamber at high pressure, ensuring proper atomization and mixing with air for efficient combustion.