Mitsubishi Eclipse. Manual — part 673

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-35

IGNITION SYSTEM

GENERAL DESCRIPTION

M1163000100250

<2.4L ENGINE>

This system is provided with two ignition coils (A and
B) with built-in ignition power transistors for the num-
ber 1 and number 4 cylinders, and number 2 and
number 3 cylinders respectively.
Interruption of the primary current flowing in the pri-
mary side of ignition coil A generates a high voltage
in the secondary side of ignition coil A.
The high voltage thus generated is applied to the
spark plugs of number 1 and number 4 cylinders to
generate sparks. At the time that the sparks are gen-
erated at both spark plugs, if one cylinder is at the
compression stroke, the other cylinder is at the
exhaust stroke, so that ignition of the compressed
air/fuel mixture occurs only for the cylinder which is
at the compression stroke.
In the same way, when the primary current flowing in
ignition coil B is interrupted, the high voltage thus
generated is applied to the spark plugs of number 2
and number 3 cylinders.

The engine control module (ECM) or power train
control module (PCM) controls the two ignition power
transistors to turn them alternately ON and OFF. This
causes the primary currents in the ignition coils to be
alternately interrupted and allowed to flow to fire the
cylinders in the order 1

− 3 − 4 − 2.

The ECM or PCM determines which ignition coil
should be controlled by means of the signals from
the camshaft position sensor which is incorporated in
the camshaft and from the crankshaft position sensor
which is incorporated in the crankshaft.
It also detects the crankshaft position in order to pro-
vide ignition at the most appropriate timing in
response to the engine operation conditions.
When the engine is cold or operated at high alti-
tudes, the ignition timing is slightly advanced to pro-
vide optimum performance.

<3.0L Engine>

Interruption of the primary current flowing in the pri-
mary side of the ignition coil generates high voltage
in the secondary side of the ignition coil. The high
voltage thus generated is directed by the distributor
to the applicable spark plug. The engine firing order
is 1

− 2 − 3 − 4 − 5 − 6 cylinders.

On application of high voltage, the spark plug gener-
ates a spark to ignite the compressed air fuel mixture
in the combustion chamber.
The engine control module (ECM) or power train
control module (PCM) makes and breaks the primary
current of the ignition coil to regulate the ignition tim-
ing.

AK100055

INTAKE AIR TEMPERATURE SENSOR

BAROMETRIC PRESSURE SENSOR

CAMSHAFT POSITION SENSOR

CRANKSHAFT POSITION SENSOR

VEHICLE SPEED SENSOR

TRANSMISSION RANGE SWITCH <A/T>

IGNITION SWITCH-ST
KNOCK SENSOR

ENGINE COOLANT TEMPERATURE
SENSOR

VOLUME AIRFLOW SENSOR

ECM
<M/T>,
PCM
<A/T>

TO TACHOMETER

IGNITION COIL A

IGNITION COIL B

IGNITION
SWITCH

BATTERY

SPARK PLUGS

CYLINDER NO.

3

2

4

1

AG

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-36

The ECM or PCM detects the crankshaft position by
the crankshaft position sensor. This sensor is
installed at the front end of the crankshaft to provide
ignition at the most appropriate timing for the engine
operating condition.

When the engine is cold, the ignition timing is slightly
advanced to provide optimum performance to the
operating condition.

SPECIAL TOOLS

M1163000600051

AKX01291

INTAKE AIR TEMPERATURE SENSOR

BAROMETRIC PRESSURE SENSOR

CRANKSHAFT POSITION SENSOR

CAMSHAFT
POSITION
SENSOR

IGNITION
POWER
TRANSIST-
OR

VEHICLE SPEED SENSOR

TRANSMISSION RANGE SWITCH <A/T>

IGNITION SWITCH-ST

KNOCK SENSOR

ENGINE COOLANT TEMPERATURE
SENSOR

VOLUME AIRFLOW SENSOR

ECM
<M/T>,
PCM
<A/T>

TO TACHOMETER

IGNITION COIL

DISTRIBUTOR

IGNITION
SWITCH

BATTERY

SPARK PLUG

AD

TOOL

TOOL NUMBER AND
NAME

SUPERSESSION

APPLICATION

MB991348
Test harness set

Tool not available

Inspection of ignition
primary voltage (Ignition
power transistor
connection)

MD998773
Knock sensor wrench

MD998773-01

Knock sensor removal
and installation

MB991348

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-37

ON-VEHICLE SERVICE

SPARK PLUG CABLE TEST

M1163000900074

<3.0L ENGINE>

WARNING

Wear rubber gloves while performing this test.

1. Disconnect, one at a time, each of the spark plug cables

while the engine is idling to check whether the engine's
running performance changes or not.

2. If the engine performance does not change, check the

resistance of the spark plug cable, and check the spark plug
itself.

IGNITION COIL CHECK

M1163001200205

<2.4L ENGINE

− With built-in ignition power

transistor>

Check by the following procedure, and replace the coil if there
is a malfunction.

.

SECONDARY COIL RESISTANCE CHECK
Measure the resistance between the high-voltage terminals of
the ignition coil.

Standard value: 8.5

− 11.5 kΩ

.

PRIMARY COIL AND IGNITION POWER TRANSISTOR
CONTINUITY CHECK

NOTE: An analog-type ohmmeter should be used.

AK101391

SPARK PLUG CABLE

AK101391AB

AKX01264

AKX01265AB

1.5 V

1 2 3

+

–

IGNITION SYSTEM

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ENGINE ELECTRICAL

16-38

NOTE: Connect the negative probe of the ohmmeter to termi-
nal 1.

CAUTION

This test must be performed quickly (in less than 10 sec-
onds) to prevent coil from burning and ignition power tran-
sistor from breaking.
As described in the chart below, perform a continuity check on
the ignition coil and power transistor.

IGNITION COIL CHECK

M1163001200078

<3.0L ENGINE>

1. Measurement of the primary coil resistance

Measure the resistance between connector terminals 1 and
2 of the distributor.

Standard value: 0.56

− 0.68 Ω

2. Measurement of the secondary coil resistance

Measure the resistance between the high-voltage terminal
and connector terminal 1.

Standard value: 9.4

− 12.8 kΩ

IGNITION COIL POWER TRANSISTOR
CONTINUITY CHECK

M1163001300097

<3.0L ENGINE>

.

NOTE: An analog-type ohmmeter should be used.
NOTE: Connect the negative probe of the ohmmeter to termi-
nal 2.

1.5 V POWER SUPPLY
BETWEEN 2

− 3

CONTINUITY BETWEEN
1

− 2

Current flowing

Yes

Current not flowing

No

AKX01266

HIGH-VOLTAGE
TERMINAL

1 2 3 4 5 6 7

AB

AKX01267

1.5 V

1 2 3 4 5 6 7

+

–

AB