Mitsubishi Eclipse. Manual - part 676

 

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Mitsubishi Eclipse. Manual - part 676

 

 

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-47

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 USING AN OSCILLOSCOPE

M1163004600097

<3.0L ENGINE>

.

MEASUREMENT METHOD

Required Special Tool:
MB991348: Test Harness Set
1. Disconnect the distributor connector and connect the test 

harness set of the special tool (MB991348) in between. All 
terminals should be connected.

AKX00282

AKX00283

AKX00284

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-48

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 trig-
ger pickup will appear at the left edge of the screen.

.

STANDARD WAVE PATTERN

AKX01282

OSCILLOSCOPE

PRIMARY
PICKUP

GROUND

1 2 3 4 5 6 7

AB

OBSERVATION CONDITIONS 

FUNCTION

SECONDARY

Pattern height

High (or low)

Pattern selector

Raster

Engine speed

Curb idle speed

AKX00286

PRIMARY
VOLTAGE
WAVE PATTERN

(V)

100

0

ZENER
VOLTAGE
(POINT C)

(APPROXIMATELY
40 

× 10 V)

DWELL SECTION

SPARK LINE
(POINT A)

WAVE DAMPING REDUCTION
SECTION (POINT B)

TIME

AB

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-49

.

WAVEFORM OBSERVATION POINTS
NOTE:  Abnormal waveform examples are shown subse-
quently.
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: 

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

OBSERVATION CONDITIONS 

Pattern selector

Display

Pattern height

High (or low)

Engine speed

Curb idle speed

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

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-50

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.

HEIGHT OF ZENER 
VOLTAGE

PROBABLE CAUSE

High

Problem in zener diode

Low

Abnormal resistance in 
primary coil circuit

AKX00288

AKX00289

AKX00290

 

 

 

 

 

 

 

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