Automobile Engineering Multiple Choice Questions on “Fuel Injection Systems”.
1. In which of the following fuel injector is used?
a) Compression-ignition engines
b) Spark-ignition engines
c) Steam engines
d) Sterling engines
Clarification: In compression – ignition (CI) engines, only air is compressed in the cylinder and by means of fuel – injection system fuel is injected into the cylinder. In CI engines, compressed air temperature plays a main role in combustion.
2. At which stroke the fuel is injected in the CI engine?
a) Suction stroke
b) Compression stroke
c) Expansion stroke
d) Exhaust stroke
Clarification: Fuel injection in the CI engines start at the end of the compression stroke. Fuel is injected directly into the combustion chamber.
3. Which of the following is the port fuel – injection system?
a) D – MPFI
b) L – MPFI
Clarification: L – MPFI system uses port fuel – injection. In this, the fuel metering is regulated by the speed of the engine and the amount of air that actually enters the engine. D – MPFI system uses manifold injection. GDI system uses direct injection. TBI system uses throttle body injection.
4. What is the range of pressure is achieved in the injection pump?
a) 120 – 200 bar
b) 10 – 20 bar
c) 400 – 500 bar
d) < 10bar
Clarification: The purpose of the fuel injection pump is to increase the pressure of the quantity of fuel in the range of 120 – 200 bars and deliver it at the correct instant to the injector.
5. In pneumatic governor, which of the following control the amount of vacuum applied to the diaphragm?
b) Accelerator pedal
c) Butterfly valve
Clarification: The vacuum applied to the diaphragm is controlled by the accelerator pedal. The diaphragm is in contact with the fuel pump control rack.
6. A six-cylinder, four-stroke diesel engine develops a power of 200 kW at 2000 revolution per minute. The brake specific fuel consumption is 0.3 kg / kW – h. What is the time for injection if the injection takes place over 20° crank angle?
a) 1 millisecond
b) 2 milliseconds
c) 1.5 milliseconds
d) 1.66 milliseconds
Clarification: Power output / cylinder = 200 / 6 = 33.33 kW. Fuel consumption / cylinder = 33.33 * brake specific fuel consumption = 33.33 * 0.3 = 9.99 kg / h. Time for injection = (20 * 60) / (360 * 2000) = 1.667 * 10-3 sec = 1.66 milliseconds.
7. What is the spray cone angle in the Pintle nozzle?
Clarification: Spray cone angle of a Pintle nozzle is 60°. The main advantage of this nozzle is that it avoids weak injection and dribbling. Also, it prevents the carbon deposition on the nozzle hole.
8. Which of the following is not the part of the injector assembly?
a) Needle valve
d) Compressor spring
Clarification: The injector assembly consists of a needle valve, nozzle, compressor spring, and an injector body. The diaphragm is a part of the injection pump governor. A nozzle is used to atomize the fuel and break up into small particles.
9. Which of the following is not the function of the fuel injection system?
a) Time the fuel injection
b) Filter the fuel
c) Atomize the fuel to fine particles
d) Control the engine speed
Clarification: The functions of the fuel injection system are to filter the fuel, to time the fuel injection, to break up the fuel into small particles.
10. The cold start injector provides a lean air-fuel ratio.
Clarification: The cold start injector gives a rich air-fuel ratio. Its objective is to supply the engine with additional fuel to make the rich mixture in cold temperatures where the air density is increased and additional fuel is required.