Mitsubishi Eclipse. Manual - part 673
IGNITION SYSTEM
TSB Revision
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