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) 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: 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) 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: A) Clogged nozzle orifices
B) Leaking nozzle seals
D) Corrosion or erosion of the nozzle tip
Explanation: Diesel engine fuel nozzles may encounter defects such as clogged nozzle orifices, leaking nozzle seals, and corrosion or erosion of the nozzle tip. These issues can impair the nozzle's performance by affecting fuel atomization, causing leakage, or altering the spray pattern, which can lead to inefficient combustion and reduced engine performance.

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: 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: 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) 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 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 fuel consumption and reduced power output
Explanation: Low compression pressure in a four-stroke engine can lead to increased fuel consumption and reduced power output. This occurs because insufficient compression pressure results in incomplete combustion of the fuel-air mixture, leading to less efficient engine performance and higher fuel usage.