Mitsubishi Galant. Manual — part 354

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-42

Point B:

Number of vibrations in reduction vibration section (Refer to
Abnormal Waveform Example 5)

Point C:

Number of vibrations at beginning of dwell section (Refer to
Abnormal Waveform Example 5)

Point D:

Ignition voltage height (distribution per each cylinder) shows
the following trends.

ABNORMAL WAVEFORMS EXAMPLES
Example 1

•

Wave characteristics
Spark line is high and short.

•

Cause of problem
Spark plug gap is too large.

Example 2

•

Wave characteristics
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.

•

Cause of problem
Spark plug gap is too small.

NUMBER OF VIBRATIONS

COIL AND CAPACITOR

Three or more

Normal

Except above

Abnormal

NUMBER OF VIBRATIONS

COIL

5

−

6 or higher

Normal

Except above

Abnormal

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

AKX00280

AKX00281

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-43

Example 3

•

Wave characteristics
Spark line is low and long, and is sloping. However, there is
almost no spark line distortion.

•

Cause of problem
Spark plug gap is fouled.

Example 4

•

Wave characteristics
Spark line is high and short. Difficult to distinguish between
this and abnormal wave pattern example 1.

•

Cause of problem
Spark plug cable is not properly connected. (Causing a dual
ignition)

Example 5

•

Wave characteristics
No waves in wave damping section

•

Cause of problem
Layer short in ignition coil.

IGNITION PRIMARY VOLTAGE WAVE PATTERN
CHECK

M1163004600020

<3.0L ENGINE>

MEASUREMENT METHOD
1. Disconnect the distributor connector and connect special

tool (Test harness: MB991348) in between. (All of the
terminals should be connected.)

2. Connect the analyzer primary pickup to the distributor

connector terminal 2.

3. Connect the primary pickup ground terminal.

4. Clamp the spark plug cable with the trigger pickup.

NOTE: The wave pattern of the cylinder clamped to the
trigger pickup will appear at the left edge of the screen.

AKX00282

AKX00283

AKX00284

AKX01282

OSCILLOSCOPE

PRIMARY
PICKUP

GROUND

1 2 3 4 5 6 7

AB

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-44

STANDARD WAVE PATTERN

OBSERVATION CONDITIONS

FUNCTION

SECONDARY

Pattern height

High (or low)

Pattern selector

Raster

Engine speed

Curb idle speed

OBSERVATION CONDITIONS

Pattern selector

Display

Pattern height

High (or low)

Engine speed

Curb idle speed

AKX00286

PRIMARY
VOLTAGE
WAVE PATTERN

(V)

100

0

ZENER
VOLTAGE
(POINT C)

(APPROXIMATELY
40

~

10V)

DWELL SECTION

SPARK LINE
(POINT A)

WAVE DAMEPING REDUCTION
SECTION(POINT B)

TIME

AB

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-45

WAVEFORM OBSERVATION POINTS

NOTE: Abnormal waveform examples are shown
subsequently.
Point A:

The height, length and slope of the spark line (refer to
abnormal waveform examples 1, 2, 3 and 4) show the
following trends.

Point B:

Number of vibrations in reduction vibration section (Refer to
Abnormal Waveform Example 5)

Point C:

Height of Zener voltage

AKX01284

(V)

10

0

IGNITION PRIMARY
VOLTAGE
WAVE PATTERN

CENTER
SECTION

TIME

AB

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

Length Short

Large

Large wear

High

Lean

Retarded

High
resistance

Height

High

Large

Large wear

High

Lean

Retarded

High
resistance

Height

Low

Small

Normal

Low

Rich

Advanced

Leak

Slope

Large

Plug is fouled

-

-

-

-

NUMBER OF VIBRATIONS

COIL, CAPACITOR

Three or higher

Except above

Normal

Abnormal