spark plugs JAGUAR XF 2009 1.G AJ133 5.0L Engine Manual

Technical TrainingNP10-V8JLR: AJ133 5.0-Liter DFI V8 Engine04/14/20093-27
Engine Management SystemIgnition Coils
IGNITION COILS
The ignition coil operates according to the laws of induc-
tion. The unit consists of two magnetically-coupled cop-
per coils (primary and secondary windings).The coil has
a 3-pin connector and incorporates an internal switching
module.
Energy is stored in the primary winding’s magnetic field
by allowing a current to flow through the primary circuit
switched by the switching module.
At the firing point the current flow is interrupted by the
ECM, which induces secondary voltage in the coil’s sec-
ondary winding.
The secondary circuit has a diode on the ground side in
order to reduce any undesired switch-on voltage, which
could lead to misfiring into the intake manifold to an
uncritical value.
The switching module will limit the primary current to a
maximum value. It also limits the maximum primary
voltage by voltage clamping. This protects the switching
module and (along with other parameters) determines
the maximum possible secondary voltage. Safety Precautions
WARNING:
• Ignition coils generate high voltages that can cause personal injury. Appropriate
safety instructions on handling high volt-
ages must be observed.
CAUTIONS:
• The spark plugs fitted are critical to the performance of the ignition and misfire
detection systems. No attempt should be
made to ‘clean’ or ‘gap’ these spark plugs.
They are very reliable and unlikely to cause
problems. If a faulty spark plug is sus-
pected, try substituting it before condemn-
ing it. It is essential that only factory-
approved spark plugs be used in service.
DO NOT attempt to use ‘equivalent’ spark
plugs, even if they are of a similar design.
Use of unapproved spark plugs will cause
the misfire detection system to malfunction
and erroneously store misfire faults.
• To avoid damage to the insulator, always use the correct specified spark plugs and correct
plug removal/refit plug socket.
NOTE: A single capacitor is used in the engine harness to
suppress interference from the ignition coil power supply.
Radio Frequency Interference Suppressor
The radio frequency interference (RFI) suppressor is
mounted on the harness carrier bracket on at the upper
rear of the engine.
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