AUTOMOTIVE SCOPE TESTING

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BRIDGWATER COLLEGE

• AUTOMOTIVE SCOPE TESTING

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OSCILLOSCOPE TESTER

• An oscilloscope is like a voltmeter. It is
  connected across, or in parallel, with the
  circuit being tested, and its most important use
  is to give information about voltage changes in a
  circuit againts time.

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OSCILLOSCOPE TESTER

• The ignition oscilloscope can have markings
  on its screen which are a number of horizontal
  lines, starting from 0KV and extending in
  increments of 5KV on the left and 10KV on the
  right side (secondary).

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OSCILLOSCOPE TESTER

• The screen can also be read from 0V extending
  in increments of 5V on the left hand side and in
  increments of 10V on the right hand side
  (primary).
• The bottom of the screen is marked off in
  degrees and percentage.
• Computer scopes may use menus for voltage and
  time.

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SECONARY OSCILLOSCOPEPATTERN
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SCOPE PATTERNS

• SECONDARY PATTERN
• PURPOSE
• TO IDENTIFY
• 1. OPEN CIRCUITS IN THE SECONDARY IGNITION
  CIRCUIT.
• 2. COMPRESSION PROBLEMS.

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• 3. FUEL FAULTS
• 4. SPARK PLUG DEFECTS
• 5. CONDENSER PROBLEMS
• 6. POINTS DEFECTS
• 7. ELECTRONIC IGNITION PROBLEMS

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SECONDARY PATTERN

• 1.You are required to build up in your work book
  a complete diagram of a secondary ignition scope
  pattern.
• 2.Answer a number of multi-choice questions.
• 3.List the ignition faults against particular
  pictures showing incorrect secondary patterns.

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SECONDARY PATTERN

• FIRING LINE

a
a
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SECONDARY PATTERN

• FIRING LINE
• Voltage required to establish the spark.
• Normally 5 to 15 KV. Maximum variation
  between cylinders 3KV

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SECONDARY PATTERN

• The required firing voltage is affected by
  secondary circuit gaps, cylinder compression and
  temperature, fuel mixture and ignition timing.

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SECONDARY PATTERN

• SPARKLINE

b
FIRING LINE
b
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SECONDARY PATTERN

• SPARK LINE
• Voltage required to maintain the spark. Max.
  height 3KV
  Max. slope 1.5KV

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SECONDARY PATTERN

• The required spark voltage and characteristics
  of the spark line are affected by the secondary
  circuit resistance, spark plug and cylinder
  conditions.

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SECONDARY PATTERN

• COIL OSCILLATIONS

c
FIRING LINE
SPARK LINE
c
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SECONDARY PATTERN

• INTERMEDIATE OSCILLATIONS
• Dissipation of remaining coil energy by
  condenser action.
• Normally at least 4 gradually diminishing
  oscillations at 2000RPM.

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SECONDARY PATTERN

• The number of coil oscillations is affected
  by engine speed and defects in the coil,
  condenser, or primary circuit.

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SECONDARY PATTERN

• START OF DWELL COIL BUILDING UP ITS MAGNETIC
  FIELD d

FIRING LINE
SPARKLINE
d
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SECONDARY PATTERN

• START OF DWELL
• The points closed signal is affected by points
  condition, alignment, spring tension and defects
  in the coil or primary circuit.

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SECONDARY PATTERN

• Points open signal is affected by points
  condition and gap, or arcing due to poor
  condenser action, primary circuit defects or high
  primary current.
• ELECTRONIC IGNITION
  Start of dwell the amplifier turns on, the end of
  dwell the amplifier turns off.
• All modern amplifiers are fitted with

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• vary dwell. Vary dwell will alter the dwell
  angle with changes of speed, if the engine speed
  is low then the dwell angle is small, as the
  engine speed increases the dwell angle will also
  increase providing a constant energy ingnition
  system.

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PRIMARY OSCILLOCOPEPATTERN
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PRIMARY PATTERN

• Since any voltage variation in the primary
  ignition circuit will be reflected in secondary
  circuit testing, it is not always necessary to
  use primary circuit testing to determine the
  general condition of the ignition system.
• The trace patterns of the primary circuit are
  very simular to that of the secondary. The
  voltage values represented in the primary
  patterns are much lower than the secondary
  patterns(primary is measured in VOLTS).

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PRIMARY PATTERN

• The diagram below shows a single cylinder
  primary pattern

250V
Firing section
Dwell section
Intermediate section
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MULTI-CHOICEQUESTIONSTYPES OF
OSCILLOSCOPEPATTERNS
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SECONDARY PATTERN

• 1. STATE THE PATTERN TYPE BELOW a)
  Superimposed b) Single cylinder
  c) Raster d) Display
• 2. State the permitted variation between
  cylinders a) 8KV b) 12KV c) 3KV d) 4KV

1
3
4
2
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SECONDARY PATTERN

• 3. NAME THE TYPE OF PATTERN BELOW a) Superimposed
  b) Raster c) Display

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SECONDARY PATTERN

• 4. Name the pattern below
  a) Raster b) Single cylinder c) Display
  d) Superinposed

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IGNITION SYSTEMFAULT DIAGNOSIS
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SECONDARY PATTERN

• MAKE A LIST AGAINST THE FOLLOWING FAULTS
• 1. No firing line or spark line

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SECONDARY PATTERN

• 2. Low firing line and long spark line

3KV
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SECONDARY PATTERN

• 3. Normal firing line and short and steep
  sparkline

8KV
5KV
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SECONDARY PATTERN

• 4. High firing line short spark line

16 KV
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SECONDARY PATTERN

• 5. Hashing when points close and open

8KV
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SECONDARY PATTERN

• 6. Pattern is upside down

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SECONDARY PATTERN

• 7. No 3 cylinder has a low firing line and long
  sparkline

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4
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1
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SECONDARY PATTERN

• 8. No 4 cylinder dwell section is out of line
  with the other cylinders

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1
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SECONDARY PATTERN

• 9. Lack of coil oscillations

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AUTOMOTIVE SCOPECONNECTIONS TO VEHICLE
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SCOPE CONNECTION

• Identify the parts of the engine the
  connections are made.

BOOM
a b c d e f g
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SCOPE CONNECTIONS

• a) Red clamp to_____________
• b) Chrome clamp to___________
• c) Green clip to_______________
• d) Yellow clip to______________
• e) Black clip to_______________
• f) Red clip to_________________
• g) Green clamp to____________