4.7 Exercises for Unit 4
1. What factor makes it possible to ignite the air-fuel mixture of a diesel
engine without the use of a spark plug as required in a gasoline engine?
- A. The ignition temperature of diesel fuel is low.
- B. The compression ratio of the diesel engine is low.
- C. The compression temperature of the diesel engine is high.
- D. The speed of the diesel engine’s moving parts is high.
2. What action controls the speed of a diesel engine?
- A. Regulation of the amount of fuel delivered to the engine’s cylinders
- B. Alteration of the compression pressure within the engine’s cylinders
- C. Regulation of the volume of air entering the cylinders
- D. Limitation of the capacity of the fuel injection system
3. Which characteristic is one advantage of the diesel engine over the gasoline
- A. Low production cost
- B. Suitability for vehicles transporting small loads
- C. Smoothness of operation
- D. High ratio of power output to fuel consumed
4. What agency is responsible for grading diesel fuel?
- A. Society of Automotive Engineers
- B. American Petroleum Institute
- C. American Society for Testing And Materials
- D. Society of Automotive Petroleum
5. What grade of diesel fuel is used in truck fleets because of its greater heat
- A. 4D
- B. 3D
- C. 2D
- D. 1D
6. Which factor must be considered when selecting a fuel oil?
- A. Engine size and design
- B. Fuel cost and availability
- C. Atmospheric conditions
- D. Speed and load range
7. The measure of the volatility of a diesel fuel is known as the _____ number.
- A. cetane
- B. octane
- C. distillation
- D. stability
8. If the cetane number of a diesel fuel is too low, which condition can result?
- A. Pre-ignition
- B. Difficulty in starting
- C. Puffs of blue smoke during start-up
- D. Detonation
9. Current diesel fuels have a cetane rating that ranges between .
- A. 50 and 60
- B. 40 and 50
- C. 30 and 40
- D. 20 and 30
10. Low volatile fuels tend to provide better fuel economy and produce .
- A. more crankcase dilution
- B. higher exhaust temperature
- C. less exhaust smoke
- D. less lubrication
11. Which property has a direct bearing on the life expectancy of the engine and
- A. Sulfur content
- B. Viscosity
- C. Volatility
- D. Cleanliness and stability
12. Which combustion chamber design is the most common?
- A. Swirl
- B. Pre-combustion
- C. Indirect
- D. Direct
13. When precombustion chambers are used on a diesel engine, which factor causes
the greatest amount of fuel atomization?
- A. Rapid air movement within the cylinders
- B. High fuel injection pressure
- C. Dispersion of fuel from the multiorifice fuel injectors
- D. Turbulence within the precombustion chamber
14. What component is designed to prevent an engine from over-speeding and allow
the engine to meet changing load conditions?
- A. Fuel pump
- B. Carburetor
- C. Throttle valve
- D. Governor
15. At what location is the governor connected on a diesel engine?
- A. Next to the fuel pump
- B. Between the throttle and the fuel injector
- C. Between the fuel pump and the fuel filter
- D. Between the fuel filter and throttle
16. What type of governor prevents an engine from exceeding a specified maximum
- A. Limiting-speed
- B. Constant-speed
- C. Variable-speed
- D. Load-control
17. What type of governor maintains any specified engine speed between idle and
- A. Load-limiting
- B. Load-control
- C. Pressure-regulating
- D. Variable-speed
18. What type of governor provides a regular or stable engine speed, regardless
of load conditions?
- 19. What part of a spring-loaded mechanical governor does the manual throttle
- A. Linkage between flyballs and injectors
- B. Spring tension
- C. Position of flyballs
- D. Centrifugal-force generator
20. The tension of the spring in the mechanical flyweight governor has a
tendency to _____.
- A. stabilize the amount of fuel delivered to the cylinders
- B. reduce the amount of fuel delivered to the cylinders
- C. increase the amount of fuel delivered to the cylinders
- D. increase and reduce the amount of fuel delivered to the cylinders
21. For engine speed to stabilize, what condition must exist within the
- A. Centrifugal force must overcome spring tension.
- B. Spring tension must overcome centrifugal force.
- C. Centrifugal force and spring tension must balance fuel supply pressure.
- D. Centrifugal force and spring tension must be equalized.
22. Which characteristic is NOT an advantage of a mechanical governor?
- A. Inexpensive to manufacture
- B. Very simple, contains few parts
- C. Large deadbands
- D. Not required to maintain the same speed, regardless of load
23. The hydraulic governor is inherently unstable. To maintain stability,
hydraulic governors employ .
- A. speed droop
- B. deadbands
- C. sensitivity
- D. isochronous
24. In an electronic governor, at what location is the magnetic pickup sensor
- A. Next to a drive shaft gear
- B. Between the crankshaft and electronic control module
- C. Between the flyweights and springs
- D. Next to the idle speed control
25. Sediment or water is prevented from entering the fuel system because the
inlet fuel line is how far from the bottom of the tank?
- A. 2 inch
- B. 1½ inch
- C. 1 inches
- D. ½ inches
26. Why is it necessary to have a supply pump to transfer fuel from the tank to
the injection pump of a diesel engine?
- A. Because the injection pump will not create sufficient suction
- B. Because the fuel filters pass fuel only under pressure
- C. Because the injection pump will deliver excessive fuel to the engine
- D. Because use of the injection pump alone will cause the fuel system to become
27. What are the five functions of a diesel fuel injection system?
- A. Measure, introduce, time, atomize, and create force
- B. Meter, inject, time, atomize, and create pressure
- C. Measure, insert, time, atomize, and catalyze
- D. Metered, introjection, timer, atomism, and catalyze
28. The rate at which fuel is injected also determines the rate of _____.
- A. combustion
- B. speed
- C. timing
- D. distribution
29. What type of injection system is used on Caterpillar diesel engines?
- A. Unit injection
- B. Pump and nozzle
- C. Distributor
- D. Pressure time
30. What action varies the metering of fuel in a Caterpillar injection system?
- A. An increase and decrease in the nozzle orifices
- B. Controlled cam and spring action
- C. Turning of the plungers in the barrels
- D. Turning of the rack and pinion
31. With the engine operating at full load, the transfer pump fills the
injection pump housing with fuel at approximately _____ psi.
- A. 10 to 15
- B. 20 to 25
- C. 30 to 35
- D. 40 to 45
32. At approximately what rate, in gallons per hour, does the constant bleed
valve return fuel back to the fuel tank?
- A. 12
- B. 9
- C. 5
- D. 2
33. What type of governor is used on the sleeve metering fuel system?
- A. Mechanical
- B. Hydraulic
- C. Electronic
- D. Hydromechanical
34. The sleeve metering fuel system uses what for lubrication?
- A. Oil
- B. Fuel
- C. Greese
- D. Not required
35. What type of seal is used to prevent engine oil from entering the DB2 fuel
- A. Two cone seals
- B. Two lip seals
- C. Two O rings
- D. Two Quad-X rings
36. What positive displacement type of transfer pump is used in the DB2 fuel
- A. Vane
- B. Rotary
- C. Electric
- D. Piston
37. What action limits the maximum amount of fuel that can be injected by the
DB2 fuel pump?
- A. Outward travel of the plungers
- B. Roller shoes contacting the leaf spring
- C. Opening of the charging ports
- D. Movement of the cam lobes
38. In the PTG-AFC fuel pump, what determines the AFC plunger position?
- A. Positive boost pressure in the exhaust manifold
- B. Positive boost pressure in the intake manifold
- C. Negative boost pressure in the intake manifold
- D. Negative boost pressure in the exhaust manifold
39. After replacing the injectors in a Cummins PT fuel system, you should
readjust them after the engine has been warmed up to within what temperature
- A. Between 160° and 180°
- B. Between 140° and 160°
- C. Between 120° and 140°
- D. Between 110° and 130°
40. When overhauling a set of PT fuel injectors, you must keep them together because they are _____ sets.
- A. matched
- B. paired
- C. connected
- D coupled
41. What drives a turbocharger?
- A. Exhaust
- B. Belt
- C. Chain
- D. Gear
42. What type of cold weather starting devices uses convection as a means to
- A. Circulating tank heater
- B. Immersion block heater
- C. Manifold flame heater
- D. Fuel-fired heater
43. Blue smoke coming from the exhaust indicates the existence of which
- A. High exhaust back pressure
- B. Water leaking into the combustion chamber
- C. Low cylinder compression from worn rings
- D. Oil entering the combustion chamber