1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 25
Diesel Injection
Fundamentals

3. Contents Basic diesel injection system
Diesel injection system accessories
Piezo diesel injectors

4. Diesel Fuel Injection System
High-pressure mechanical system that delivers fuel directly into the combustion chambers
Unlike a lower-pressure gasoline system, which meters fuel into the intake manifold

5. Diesel versus Gasoline
High compression
17:1 to 25:1
Compression ignition
No throttle valve
Compresses air
Direct injection into combustion chamber
Engine power controlled by the amount of fuel injected
Lower compression
8:1 to 10:1
Spark ignition
Throttle valve
Compresses air/fuel
Fuel metered into intake manifold
Engine power controlled by regulating air and fuel flow

6. Diesel Injection System
Injection pump plunger produces high pressure to open the injector

7. Components Injection pump Injection lines
high-pressure mechanical pump
meters fuel to each injector nozzle at the proper time
Injection lines
high-strength steel tubing
carry fuel to each injector nozzle

8. Components Injector nozzles Glow plugs spring-loaded valves
spray fuel into each combustion chamber
Glow plugs
electric heating elements
warm air in the cylinder precombustion chambers
aid starting of a cold engine

9. Components
Diesel fuel supply system feeds fuel from the fuel tank to the injection pump
Components
inline pump
filters and water separator to clean the fuel
fuel return lines to carry unused fuel back to the tank

10. Complete Diesel System
Supply pump feeds the injection pump

11. Diesel Injection Pumps
Bolted to the top or side of the engine
Meter correct amount of fuel to the injectors
Time fuel injection
Control idle speed and maximum speed
Provide a means of shutting off the engine

12. Located on the right side of the engine
Diesel Injection Pump
Located on the right side of the engine

13. Inline Injection Pump Components
Camshaft acts on roller tappet
Tappet pushes on plunger

14. Camshaft Operates one plunger per cylinder
When the engine turns the pump camshaft, lobes push on the roller tappets to move them up, forcing plungers up
Plunger return springs force plungers back down as the lobes rotate away from the roller tappets

15. Pump Plungers
Small pistons that slide in individual barrels to push fuel
Plungers pressurize the fuel, forcing it through the injector lines and to the injector nozzles

16. Inline Pump Components
Control sleeves alter amount of fuel to each injector nozzle

17. Control Rod or Rack Delivery Valves
Toothed shaft
Acts as a throttle to control speed and power
Rotates the control sleeves
Delivery Valves
Spring-loaded valves in the outlets to the injection lines
Ensure quick, leak-free closing of the injector nozzles

18. Pump Operation Fuel supply pump fills the barrel with fuel
Camshaft forces the roller tappet and plunger upward in the barrel
Fuel is forced through the delivery valve, through the injection line, and out the nozzle
Delivery valve closes when the plunger reaches the end of its stroke

19. Plunger action in an inline pump
Pump Operation
Plunger action in an inline pump

20. Metering The rack slides across the control sleeves to rotate them
A helix-shaped (spiral) groove and a slot are cut into the side of the plunger
When the helix is aligned with the port (hole) in the side of the barrel, the plunger cannot develop pressure
Fuel flows down the slot, through the helix groove, and out the port

21. Control rack is linked to the gas pedal and governor
Metering
Control rack is linked to the gas pedal and governor

22. Effective Plunger Stroke
Amount of plunger movement that pressurizes the fuel
When the plunger moves up and the helix is not aligned with the port, fuel is trapped and pressurized
Sleeve rotation regulates how much fuel is injected

23. Controls idle speed and limits maximum engine speed
Inline Pump Governor
Controls idle speed and limits maximum engine speed

24. Governor Operation Uses weights, springs, and levers
Levers are connected to control rack
As engine speed increases, weights are thrown outward (centrifugal force)
This moves the levers and control rack to reduce effective plunger stroke
Engine speed is limited

25. Governor Operation
When driver presses the gas pedal, throttle lever spring pressure overcomes governor spring pressure
The control rack is moved to increase fuel delivery (effective plunger stroke is increased)
When engine speed reaches the desired level, the governor overcomes throttle lever spring pressure

26. Governor Operation

27. Governor Operation

28. Accelerator-Injection Pump Linkage

29. Injection Timing
Relationship between the moment fuel is injected into cylinder and piston position
Controlled by spring-loaded weights in an inline injection pump
As engine speed increases, weights fly outward to advance injection timing, providing more time to ignite and burn fuel

30. Injection Pump Fuel Flow

31. Distributor Injection Pumps
Only one or two plungers supply fuel for all the cylinders
Most common type of pump used on passenger cars
There are two common types of distributor injection pumps:
single-plunger pumps
two-plunger pumps

32. Single-Plunger Pumps
Components
Operation
Metering
Timing

33. Single-Plunger Pump Components

34. Transfer Pump Cam Plate
Forces fuel into the injection pump
Lubricates injection pump
Fills the pumping chambers
Cam Plate
Rotating lobed disc
Operates plunger
Forces plunger to move and develop injection pressure

35. Fuel Metering Sleeve Hydraulic Head
Can be slid sideways on the plunger to change effective plunger stroke
Surrounds the plunger
Hydraulic Head
Housing around the plunger
Contains passages for filling the barrel and injecting fuel into the delivery valves

36. Centrifugal Governor Controls amount of fuel injected and engine speed
Flyweight action moves the metering sleeve to limit top speed

37. Note the system fuel flow
Single-Plunger Pump
Note the system fuel flow

38. Single-Plunger Pump Operation
As the shaft rotates, the fill port in the hydraulic head lines up with the port in the plunger
The transfer pump forces fuel into the high-pressure chamber in front of the plunger
The fill port moves out of alignment
The injection port lines up
The cam plate lobe pushes the plunger sideways, forcing fuel to the injector nozzle

39. Metering

40. Injection Timing As speed increases, injection must occur sooner
Transfer pump turns faster, increasing pressure output
Increased pressure moves an injection advance piston
Cam plate ramps engage plunger sooner

41. Vane pump pressure can be used to control injection timing

42. Two-Plunger Pump

43. Two-Plunger Pump Components
Two plungers
force fuel to each injector nozzle
Distributor rotor
controls fuel flow to each injector nozzle
Internal cam ring
acts as a cam to force plungers inward
Fuel metering valve
regulates injection quantity by controlling how far plungers move apart on the fill stroke

44. Two-Plunger Pump Operation
The transfer pump pulls fuel into the injection pump
When charging ports line up, fuel fills the high-pressure chamber
Charging ports move out of alignment
Discharge ports line up
Plungers are forced inward by the cam ring, forcing fuel out of the hydraulic head and to the injector nozzles

45. Injector Nozzles
Spring-loaded valves that spray fuel directly into precombustion chambers

46. Injector Nozzle Construction

47. Injector Nozzle Operation
High pressure fuel flows into the injector nozzle inlet
Fuel flows down the fuel passage in the body into the pressure chamber
The needle is forced upward, compressing the spring
Fuel sprays out in a conical pattern
Fuel that leaks past the needle returns to the fuel tank through return lines

48. Injector Nozzle Operation
With enough injection pressure, the needle valve is pushed up and fuel sprays into the precombustion chamber

49. Inward Opening Nozzles

50. Spray patterns for different types of injectors
Nozzle Types
Spray patterns for different types of injectors

51. Glow Plugs Heating elements that warm air in precombustion chambers
Threaded into the cylinder head
Control circuit automatically disconnects the glow plugs after a few seconds of operation

52. Tip protrudes into the precombustion chamber
Glow Plug
Tip protrudes into the precombustion chamber

53. Glow Plug
Current flow through the plug heats the element to warm air in the precombustion chamber

54. Control Circuit Components
Engine coolant temperature sensor
Glow plug control unit
Indicator lights

55. Glow Plug Circuit

56. Engine Temperature Sensor
Senses coolant temperature
Feeds data to control unit
If engine is warm, the control unit will not turn on glow plugs

57. Indicator Lights Operated by control unit
Inform driver if engine is ready to start because glow plugs are fully heated

58. Glow Plug Operation Engine cold The driver turns on ignition switch
High current flows from battery to glow plugs
Glow plugs heat to a dull red glow
When the indicator light goes out, the engine is ready to crank
Glow plug heat supplements the heat of compression to ignite mixture

59. Diesel Injection System
Accessories
Water detector
Fuel heater
Block heater
Vacuum pump

60. Water Detector Fuel Heater
Warns driver of water in fuel
Water and other contaminants are very harmful to the fuel injection pump and injectors
Fuel Heater
May be used to warm diesel fuel
Prevents fuel from jelling in very cold weather
Electric heating element is located in the fuel line, ahead of the injection pump

61. Water Detector and Fuel Heater

62. Diesel Injection Electrical Circuit

63. Block Heater May be used to warm the engine in cold weather
Cold starting aid
Heating device plugs into wall electric outlet

64. Vacuum Pump
Diesel engines have little manifold vacuum since there is no throttle valve
Provides a source of vacuum for vehicle systems:
power brakes
A/C ventilation controls
emission control devices (EGR)

65. Diaphragm Vacuum Pump

66. Mounted in back of the alternator
Vane-Type Vacuum Pump
Mounted in back of the alternator

67. Computer-Controlled Diesel
Uses a computer, sensors, and actuators to increase efficiency

68. Injection Pump Solenoids
Control injection timing and quantity
Controlled by the computer
When energized or de-energized electrically, solenoids open or close fuel passages to alter pump operation

69. Diesel Injection Sensors
Monitor temperature, speed, and other variables that affect fuel needs
Similar to those on gasoline systems

70. Diesel Injection Computer
Monitors sensor inputs
Calculates fuel needs
Controls outputs such as pump solenoids and emission control devices
Precisely controls mechanical high-pressure plungers inside the injection pump

71. Piezo Diesel Injectors
Use piezoelectric crystals to meter fuel
Provide precise fuel metering
Reduce exhaust emissions
Produce smoother engine operation

72. Piezoelectric Crystals
Used to open or close injector needle
When current is applied, crystal expands and forces injector needle open
When polarity is reversed, crystal contracts and closes injector needle
Rapid operation allows for more precise timing

73. Piezo Diesel Injector
Current flow causes piezoelectric element to open or close needle valve