Mitsubishi Space Star. Manual — part 98
ENGINE ELECTRICAL –
Ignition System
16-11
IGNITION FAILURE SENSOR CHECK
NOTE
An analog-type circuit tester should be used.
Check that the resistance between terminals 3 and 4 is at
the standard value.
Standard value: 0.1
Ω
or less
WAVEFORM CHECK USING AN ANALYZER
<4G13-MPI>
Ignition Secondary Voltage Waveform Check
MEASUREMENT METHOD
1.
Clamp the secondary pickup around the spark plug cable.
NOTE
(1) The peak ignition voltage will be reversed when the
spark cables No. 2 and No. 4, or No. 1 and No. 3
cylinders are clamped.
(2) Because of the two-cylinder simultaneous ignition
system, the waveforms for two cylinders in each group
appear during waveform observation (No. 1 cylinder
– No. 4 cylinder, No. 2 cylinder – No. 3 cylinder).
However, waveform observation is only applicable for
the cylinder with the spark plug cable clamped by
the secondary pickup.
(3) Identifying which cylinder waveform is displayed can
be difficult. For reference, remember that the waveform
of the cylinder attached to the secondary pickup will
be displayed as stable.
2.
Clamp the spark plug cable with the trigger pickup.
NOTE
Clamp the trigger pickup to the same spark plug cable
clamped by the secondary pickup.
ENGINE ELECTRICAL –
Ignition System
16-12
STANDARD WAVEFORM
Observation Conditions
Function
Secondary
Pattern height
High (or Low)
Pattern selector
Raster
Engine revolutions
Curb idle speed
kV
Secondary
ignition
voltage
waveform
Ignition voltage
(point D)
Dwell
section
Point C
Spark line (point A)
Wave damping
reduction section
(point B)
Time
Observation Condition (The only change from above condition is the pattern selector.)
Pattern selector
Display
Secondary
ignition
voltage
waveform
kV
No. 4 cylinder
No. 2 cylinder
ignition noise
No. 1 cylinder
No. 3 cylin-
der ignition
noise
Neutral section
0
2
Time
ENGINE ELECTRICAL –
Ignition System
16-13
WAVEFORM OBSERVATION POINTS
Point A: The height, length and slope of the spark line show the following trends (Refer to abnormal
waveform examples, 1, 2, 3 and 4).
Spark line
Plug gap
Condition of
electrode
Compression
force
Concentration of
air mixture
Ignition timing
Spark plug
cable
Length
Long
Small
Normal
Low
Rich
Advanced
Leak
Short
Large
Large wear
High
Lean
Retarded
High
resistance
Height
High
Large
Large wear
High
Lean
Retarded
High
resistance
Low
Small
Normal
Low
Rich
Advanced
Leak
Slope
Large
Plug is fouled
–
–
–
–
Point B: Number of vibration in reduction vibration section (Refer to abnormal waveform example 5).
Number of vibrations
Coil and condenser
Three or more
Normal
Except above
Abnormal
Point C: Number of vibrations at beginning of dwell section (Refer to abnormal waveform example 5).
Number of vibrations
Coil
5 – 6 or higher
Normal
Except above
Abnormal
Point D: Ignition voltage height (distribution per each cylinder) shows the following trends.
Ignition
voltage
Plug gap
Condition of
electrode
Compression
force
Concentration of
air mixture
Ignition timing
Spark plug cable
High
Large
Large wear
High
Lean
Retarded
High resistance
Low
Small
Normal
Low
Rich
Advanced
Leak
ENGINE ELECTRICAL –
Ignition System
16-14
EXAMPLES OF ABNORMAL WAVEFORMS
Abnormal waveform
Wave characteristics
Cause of problem
Example 1
01P0215
Spark line is high and short.
Spark plug gap is too large.
Example 2
Spark line is low and long, and is
sloping.
Also, the second half of the spark line
is distorted. This could be a result of
misfiring.
Spark plug gap is too small.
Example 3
Spark line is low and long, and is
sloping. However, there is almost no
spark line distortion.
Spark plug gap is fouled.
Example 4
Spark line is high and short.
Difficult to distinguish between this
and abnormal waveform example 1.
Spark plug cable is nearly falling off.
(Causing a dual ignition)
Example 5
No waves in wave damping section.
Rayer short in ignition coil.
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