Download SCOPE PATTERNS

BRIDGWATER COLLEGE
AUTOMOTIVE SCOPE
TESTING
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 it’s
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
OSCILLOSCOPE
PATTERN
SCOPE PATTERNS
SECONDARY PATTERN
PURPOSE
TO IDENTIFY:
1. OPEN CIRCUITS IN
THE SECONDARY
IGNITION CIRCUIT.
2. COMPRESSION
PROBLEMS.
3. FUEL FAULTS
4. SPARK PLUG DEFECTS
5. CONDENSER PROBLEMS
6. POINTS DEFECTS
7. ELECTRONIC IGNITION
PROBLEMS
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.
SECONDARY PATTERN
FIRING LINE = a
a
SECONDARY PATTERN
FIRING LINE
Voltage required to establish the spark.
Normally 5 to 15 KV. Maximum
variation between cylinders 3KV
SECONDARY PATTERN
The required firing voltage is affected by
secondary circuit gaps, cylinder
compression and temperature, fuel
mixture and ignition timing.
SECONDARY PATTERN
SPARKLINE = b
FIRING LINE
b
SECONDARY PATTERN
SPARK LINE
Voltage required to maintain the spark.
Max. height 3KV
Max. slope 1.5KV
SECONDARY PATTERN
The required spark voltage and
characteristics of the spark line are
affected by the secondary circuit
resistance, spark plug and cylinder
conditions.
SECONDARY PATTERN
COIL OSCILLATIONS = c
FIRING LINE
SPARK LINE
c
SECONDARY PATTERN
INTERMEDIATE OSCILLATIONS
Dissipation of remaining coil energy by
condenser action.
Normally at least 4 gradually diminishing
oscillations at 2000RPM.
SECONDARY PATTERN
The number of coil oscillations is
affected by engine speed and defects in
the coil, condenser, or primary circuit.
SECONDARY PATTERN
START OF DWELL COIL BUILDING
UP IT’S MAGNETIC FIELD = d
FIRING LINE
SPARKLINE
d
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.
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
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.
PRIMARY OSCILLOCOPE
PATTERN
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).
PRIMARY PATTERN
The diagram below shows a single
cylinder primary pattern
250V
Firing section
Intermediate
section
Dwell
section
MULTI-CHOICE
QUESTIONS
TYPES OF OSCILLOSCOPE
PATTERNS
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
SECONDARY PATTERN
3. NAME THE TYPE OF PATTERN BELOW
a) Superimposed b) Raster c) Display
SECONDARY PATTERN
4. Name the pattern below
a) Raster b) Single cylinder c) Display
d) Superinposed
IGNITION SYSTEM
FAULT DIAGNOSIS
SECONDARY PATTERN
MAKE A LIST AGAINST THE
FOLLOWING FAULTS
1. No firing line or spark line
SECONDARY PATTERN
2. Low firing line and long spark line
3KV
SECONDARY PATTERN
3. Normal firing line and short and steep
sparkline
8KV
5KV
SECONDARY PATTERN
4. High firing line short spark line
16 KV
SECONDARY PATTERN
5. Hashing when points close and open
8KV
SECONDARY PATTERN
6. Pattern is upside down
SECONDARY PATTERN
7. No 3 cylinder has a low firing line and long
sparkline
2
4
3
1
SECONDARY PATTERN
8. No 4 cylinder dwell section is out of line with
the other cylinders
2
4
3
1
SECONDARY PATTERN
9. Lack of coil oscillations
AUTOMOTIVE SCOPE
CONNECTIONS TO
VEHICLE
SCOPE CONNECTION
Identify the parts of the engine the
connections are made.
BOOM
a b c d e f g
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____________