Mitsubishi Montero (2004+). Manual — part 396

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-39

Observation conditions (Only pattern selector below
changes from the above conditions.)

Pattern selector

Display

AKX00286

PRIMARY
VOLTAGE
WAVE PATTERN

(V)

100

0

ZENER
VOLTAGE
(POINT C)

(APPROXIMATELY
40

× 10 V)

DWELL SECTION

SPARK LINE
(POINT A)

WAVE DAMEPING REDUCTION
SECTION (POINT B)

TIME

AB

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-40

.

WAVEFORM OBSERVATION POINTS
Point A:

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

Point B:

SPARK LINE

PLUG
GAP

CONDITION
OF
ELECTRODE

COMPRES-
SION FORCE

CONCENT-
RATION 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

−

−

−

−

AKX00287

PRIMARY
IGNITION VOLTAGE
WAVE PATTERN

TIME

NO.1 (OR NO.4)
CYLINDER

NO.4 (OR NO.1)
CYLINDER

NO.2 (OR NO.5)
CYLINDER
IGNITION NOISE

NO.5 (OR NO.2)
CYLINDER
IGNITION NOISE

NO.3 (OR NO.6)
CYLINDER
IGNITION NOISE

NO.6 (OR NO.3)
CYLINDER
IGNITION NOISE

NEUTRAL
SECTION

AB

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-41

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

Point C:

Height of Zener voltage

.

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.

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.

NUMBER OF VIBRATIONS

COIL, CAPACITOR

3 or higher

Except above

Normal

Abnormal

HEIGHT OF ZENER
VOLTAGE

PROBABLE CAUSE

High

Problem in zener diode

Low

Abnormal resistance in
primary coil circuit

AKX00288

AKX00289

AKX00290

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-42

Example 4

• Wave characteristics

Spark line is high and short

• 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.

AKX00291

AKX00292