We were recently investigating the engine area of our 2001 Jeep Grand Cherokee, and noticed the spark plugs (4L 6cyl) are connected with a power rail and what appears to be small wires to each plug.
I looked around, but could not find an article showing how this has replaced the plug & ignition wire ?
Any photos or explanations of the power rail vs traditional ignition setups.
OPERATION
The 4.0L 6-cylinder engine uses a one-piece coil
rail containing three independent coils. Although cylinder
firing order is the same as 4.0L engines of previous
years, spark plug firing is not. The 3 coils dualfire
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 atthe rear end of the coil rail) is used for all three coils.
Because of coil design, spark plug cables (secondary
cables) are not used on either engine. A distributor
is not used with either the 4.0L or 4.7L
engines.
The ignition system is controlled by the powertrain
control module (PCM) on all engines.
The ignition system consists of:
Spark Plugs
Ignition Coil(s)
Powertrain Control Module (PCM)
Crankshaft Position Sensor
Camshaft Position Sensor
The MAP, TPS, IAC and ECT also have an effect
on the control of the ignition system.
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