Ignition System Description And Operation - Jeep Cherokee 2000 Service Manual

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DESCRIPTION AND OPERATION
IGNITION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . 1
DISTRIBUTOR-2.5L ENGINE. . . . . . . . . . . . . . . . . 2
SPARK PLUGS . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
SPARK PLUG CABLES-2.5L ENGINE . . . . . . . . . . 2
IGNITION COIL-2.5L ENGINE . . . . . . . . . . . . . . . . 3
IGNITION COIL—4.0L ENGINE. . . . . . . . . . . . . . . 3
CRANKSHAFT POSITION SENSOR. . . . . . . . . . . . 4
CAMSHAFT POSITION SENSOR-2.5L ENGINE. . . 4
CAMSHAFT POSITION SENSOR—4.0L
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
IGNITION SWITCH AND KEY LOCK
CYLINDER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DIAGNOSIS AND TESTING
DISTRIBUTOR CAP-2.5L ENGINE. . . . . . . . . . . . . 6
DISTRIBUTOR ROTOR-2.5L ENGINE . . . . . . . . . . 6
SPARK PLUG CABLES . . . . . . . . . . . . . . . . . . . . . 7
SPARK PLUG CONDITIONS . . . . . . . . . . . . . . . . . 8
IGNITION SWITCH AND KEY LOCK
CYLINDER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
REMOVAL AND INSTALLATION
SPARK PLUG CABLES . . . . . . . . . . . . . . . . . . . . 10
DESCRIPTION AND OPERATION
IGNITION SYSTEM
DESCRIPTION
Two different ignition systems are used. One type
is used for the 2.5L 4–cylinder engine. The other is
used for the 4.0L 6–cylinder engine.
OPERATION
2.5L 4–Cylinder Engine:
The ignition system is controlled by the Powertrain
Control Module (PCM).
The ignition system consists of:
• Spark Plugs
• Ignition Coil
• Secondary Ignition Cables
• Distributor (contains rotor and camshaft position
sensor)
• Powertrain Control Module (PCM)
• Crankshaft Position, Camshaft Position, Throt-
tle Position and MAP Sensors
IGNITION SYSTEM
TABLE OF CONTENTS
page
SPARK PLUGS . . . . . . . . . . . . . . . . . . . . . . . . . . 10
IGNITION COIL—2.5L ENGINE. . . . . . . . . . . . . . 12
IGNITION COIL—4.0L ENGINE. . . . . . . . . . . . . . 12
CRANKSHAFT POSITION (CKP) SENSOR . . . . . 13
CAMSHAFT POSITION SENSOR—2.5L
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
CAMSHAFT POSITION SENSOR—4.0L
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
DISTRIBUTOR—2.5L ENGINE . . . . . . . . . . . . . . 17
IGNITION SWITCH AND KEY CYLINDER . . . . . . 20
SHIFTER/IGNITION INTERLOCK . . . . . . . . . . . . . 22
SPECIFICATIONS
IGNITION TIMING. . . . . . . . . . . . . . . . . . . . . . . . 23
ENGINE FIRING ORDER—2.5L 4-CYLINDER
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
ENGINE FIRING ORDER—4.0L 6-CYLINDER
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SPARK PLUGS . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SPARK PLUG CABLE RESISTANCE . . . . . . . . . . 23
IGNITION COIL RESISTANCE—2.5L ENGINE . . 23
IGNITION COIL RESISTANCE—4.0L ENGINE . . 23
TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.0L 6–Cylinder Engine:
The 4.0L 6–cylinder engine uses a one-piece coil
rail containing three independent coils. Although cyl-
inder firing order is the same as 4.0L engines of pre-
vious years, spark plug firing is not. The 3 coils dual-
fire the spark plugs on cylinders 1–6, 2–5 and/or 3–4.
When one cylinder is being fired (on compression
stroke), the spark to the opposite cylinder is being
wasted (on exhaust stroke). The one-piece coil bolts
directly to the cylinder head. Rubber boots seal the
secondary terminal ends of the coils to the top of all
6 spark plugs. One electrical connector (located at
the rear end of the coil rail) is used for all three coils.
Because of coil design, spark plug cables (second-
ary cables) are not used on either engine. A distrib-
utor is not used with the 4.0L engine.
The ignition system is controlled by the Powertrain
Control Module (PCM).
The ignition system consists of:
• Spark Plugs
• Ignition Coil(s)
• Powertrain Control Module (PCM)
IGNITION SYSTEM 8D - 1
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