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Modern Automotive

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by Russell Krick Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois Advanced diagnostics Vacuum and pressure gauge tests Vacuum pump tests Diesel engine ... – PowerPoint PPT presentation

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Title: Modern Automotive


1
PowerPoint for
Modern Automotive Technology
by Russell Krick
2
Chapter 46
Advanced Diagnostics
3
Contents
  • Advanced diagnostics
  • Vacuum and pressure gauge tests
  • Vacuum pump tests
  • Diesel engine testers
  • Advanced scan tools
  • Checking computer terminal values
  • Using a breakout box
  • (Continued)

4
Contents
  • Isolating electromagnetic interference
  • Using a digital pyrometer
  • Finding temperature-related performance problems
  • Using a dynamometer
  • Using an oscilloscope
  • Engine analyzer (computer analyzer)

5
Advanced Diagnostics
Advanced methods used to troubleshoot
difficult-to-locate problems
6
Diagnostic Techniques and Tools
  • By using some advanced techniques and tools, a
    technician can diagnose the most difficult
    problems
  • Some tools that may be used
  • vacuum and pressure gauge
  • scan tool
  • breakout box
  • engine analyzer with oscilloscope

7
Strategy-Based Diagnostics
8
Troubleshooting Chart
9
Vacuum and Pressure Gauge Tests
10
Vacuum Gauge
  • Measures pressure that is lower than atmospheric
    pressure
  • Used for
  • fuel pump vacuum tests
  • vacuum pump testing
  • intake manifold vacuum testing
  • vacuum solenoid testing

11
Pressure Gauge
  • Measures pressure that is higher than atmospheric
    pressure
  • Used for
  • fuel pump output pressure testing
  • turbocharger boost testing
  • exhaust back pressure testing

12
Vacuum Gauge Diagnosis
13
Vacuum-Pressure Gauge
  • Set up to measure boost on a road test

14
Vacuum Pump Tests
  • Used to check vacuum-actuateddevices and vacuum
    diaphragms

15
Hand Vacuum Pump
  • Connect the pump, pump the handle, and see if the
    device holds a vacuum

16
Diesel Engine Testers
  • A set of pressure gauges and valves used to
    measure injector system pressure
  • Measure various operating parameters
  • fuel pump pressure and volume
  • injector operation
  • lubrication system pressure

17
Diesel Engine Testers
18
Advanced Scan Tools
  • In addition to retrieving trouble codes, modern
    scan tools can be used for advanced diagnostic
    procedures

19
Advanced Scan Tool Tests
  • Snapshot
  • instantaneous reading of the operating parameters
    present when a problem occurs
  • useful when intermittent problems occur
  • program the scan tool for a road test
  • when the symptom occurs, capture the data
  • return to the shop and review the snapshot data

20
Advanced Scan Tool Tests
  • Datastream
  • live electrical values
  • read the scan tool screen to see computer input
    and output values

21
(No Transcript)
22
Advanced Scan Tool Tests
  • Actuator tests
  • most scan tools can switch computer-controlled
    actuators on and off
  • allows the technician to verify operation
  • the scan tool can fire an ignition coil, control
    the idle speed motor, disable a fuel injector,
    and perform a balance test

23
Checking Computer Terminal Values
24
Computer Terminal Voltage Checks
  • Use a digital voltmeter
  • Probe between the computer terminals and ground
  • Do not pierce the wires
  • Compare the terminal voltages to specified values

25
Terminal Voltage Chart
26
Breakout Box
  • Allows the technician to check electrical values
    at specific pins on an ECM or in the system the
    ECM controls
  • Inserted into wiring harness at the ECM

27
Breakout Box
28
Isolating Electromagnetic Interference
29
Electromagnetic Interference
  • Occurs when an induced voltage enters another
    systems wiring
  • Sources
  • loose, misrouted, or unshielded plug wires
  • police and CB radios
  • aftermarket accessories
  • May cause noise in stereo speakers or a
    computer-controlled system malfunction

30
Isolating Interference
  • Turn off or disable circuits or devices
  • remove the alternator drive belt
  • turn accessories on and off
  • If the problem goes away, the cause has been
    isolated
  • Use an AM radio tuned between stations to probe
    for sources

31
Using a Digital Pyrometer
32
Digital Pyrometer
  • An electronic device used to measure temperature
  • engine operating temperature
  • exhaust temperaturecatalytic converter
  • coolant temperature
  • sensor temperature
  • ambient temperature
  • air conditioning system temperatures

33
Finding Temperature-Related Performance Problems
34
Finding Temperature-Related Problems
  • Freeze spray on the ECM

35
Finding Temperature-Related Problems
  • Heat gun on the ECM

36
Using a Dynomometer
37
Dynamometer
  • Measures power output by loading the engine
  • Check acceleration, maximum power, and on-road
    performance characteristics

38
Dynamometer
  • Using a five-gas analyzer witha dynamometer

39
Using a Oscilloscope
40
Oscilloscope
  • Displays voltages in relation to time
  • Produces a line on a cathode ray tube or liquid
    crystal screen

41
Oscilloscope Screen
  • A. 25,000 volt scale
  • B. 50,000 volt scale
  • C. Time scale milliseconds
  • D. Time scale degrees

42
Scope Sweep Rate
  • Frequency or time division on screen
  • Affects the horizontal, or time, measurement
  • Set to match the waveform frequency to be
    analyzed
  • a low sweep rate compresses the signal
  • a high sweep rate expands the signal

43
Ignition Patterns
  • Primary
  • low voltage ignition components
  • the secondary circuit cannot work properly unless
    the primary circuit is in good condition
  • Secondary
  • high voltages needed to fire the spark plugs

44
Primary Waveform
45
Secondary Waveform
46
Scope Test Patterns
  • A. Superimposed display
  • Patterns on top of each otherchecks that all
    patterns are uniform

B. Parade display Patterns side by side in
firing ordercompares firing voltages
C. Stacked display Cylinders one above the
othercompares duration of events
47
Distributorless Waveform
  • True spark is on compression stroke
  • Wasted spark is on exhaust stroke

48
Magnetic Sensor Pattern
  • Probe across sensor leads

49
Hall-Effect Sensor
  • Oscilloscope connection

50
Hall-Effect Sensor Pattern
  • The sensor signal frequency should increase as
    engine speed increases

51
Optical Sensor Pattern
  • If the shutter widths vary, the pulse widths vary

52
Crankshaft Position Sensor
  • Oscilloscope connection

53
Crankshaft Position Sensor Pattern
54
Throttle Position Sensor
  • Scope connection

55
Throttle Position Sensor Pattern
  • The TPS should produce a smooth curve as the
    throttle is opened and closed

56
Throttle Position Sensor Pattern
  • A switching-type TPS should produce a good square
    wave without ringing

57
MAP Sensor
  • Scope connection

58
MAP Sensor Pattern
  • The digital waveform frequency should increase as
    engine speed increases

59
MAP Sensor Pattern
  • Analog waveform amplitude should increase as
    engine speed increases

60
Mass Airflow Sensor
  • Jumpers connect power to the sensor

61
Mass AirflowSensor Pattern
  • As flow increases, an analog airflow meter should
    produce more voltage

62
Mass AirflowSensor Pattern
  • A digital waveform frequency usually increases
    with airflow

63
Knock Sensor
  • Oscilloscope connection

64
Knock Sensor Pattern
  • Analog waveform

65
Electronic FuelInjector Patterns
  • A. Normal
  • B. Stuck
  • C. Open
  • D. Partial short

66
ECM Scope Tests
  • Oscilloscope connection

67
ECM Scope Tests
  • Reference voltage

68
Flight Record Test
  • Stores the sensor waveforms in a scopes memory
    for playback after a road test
  • Useful for checking an intermittent condition

69
Flight Record Test
  • Normal, consistent signal
  • Signal breakdown

70
Engine Analyzer
71
Engine Analyzer
  • Group of test instruments in a large, roll-around
    cabinet
  • scope
  • tach-dwell meter
  • volt-ohmmeter
  • exhaust gas analyzer
  • May be equipped with a modem to allow
    communication over telephone lines

72
Engine Analyzer
73
AnalyzerDigital Display
  • Cranking tests Running tests

74
Analyzer Connection
  • Coil separate from distributor

Unitized coildistributor
75
Analyzer Connection
  • Distributorless ignition

76
Analyzer Connection
  • Direct ignition

77
Analyzer Connection
  • Make sure all leads are clear ofhot or moving
    parts

78
Coil Output Test
  • Measures the maximum available voltage produced
    by the ignition coil
  • Spark plug requires 520 kV
  • Coil should have higher reserve voltage

79
Coil Output Test
  • Run engine at 10001500 rpm
  • Select secondary parade pattern
  • Note the spark plug firing voltages
  • Using insulated pliers, disconnect a plug wire
    (or install a spark tester before startup)
  • The open circuit should cause one firing line to
    rise to maximum coil output
  • Reconnect as soon as possible

80
Load Test
  • Snap acceleration test
  • Measures the spark plug firing voltage when an
    engine is accelerated
  • voltage requirements increase
  • Set the scope to parade
  • Quickly open and release the throttle valve
  • The firing lines should be no more than 75 of
    coil output, or about 1520 kV

81
Cylinder Balance Test
  • Measures the power output from each of the
    engines cylinders
  • The analyzer kills the spark of a selected
    cylinder, allowing the technician to observe and
    compare the rpm drop
  • All cylinders should have the same percentage of
    rpm drop (within 5)

82
Cranking Balance Test
  • Checks the engines mechanical condition
  • Measures how much current is drawn by the starter
    motor as each cylinder goes through its
    compression stroke
  • High current means high compression pressure
  • Low current means low compression pressure

83
Cranking Balance Test
  • All cylinders have the same compression

Lower compression on cylinder 5
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