Ignition Control - 4.0L/4.7L: 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 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.

The 4.7L V-8 engine uses 8 dedicated and individually fired coil for each spark plug. Each coil is mounted directly to the top of each spark plug. A separate electrical connector is used for each coil.

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.