The ignition system includes a breakerless distributor, amplifier module, an ignition coil, ignition switch, and battery. See Fig. 1. No ballast resistor is required.
The distributor has conventional centrifugal and vacuum advance systems, an anti-flash shield, rotor, reluctor, and pick-up coil. See Fig. 2. The reluctor is a gear-shaped component with 12 teeth, one for each cylinder.
The pick-up coil includes a winding, pole piece and a permanent magnet. A 2-wire shielded harness connects it directly to the amplifier module. The amplifier module, housed in an aluminum case, is located near the distributor.
On XJS models, 2 ignition coils are used. See Fig. 1. Main coil is connected in parallel with primary windings of auxiliary coil. The secondary circuit of auxiliary coil is not used and coil tower is sealed. Amplifier modules are not interchangeable between models.
Fig. 1: Wiring Schematic for Ignition System
As distributor shaft turns, reluctor turns with it. Refer to Fig. 2. As each of the 12 teeth pass across the pick-up coil's pole piece, the magnetic field strength around the pick-up winding is intensified. This creates a voltage in pick-up coil winding.
The rise and fall of this voltage is sensed by the amplifier module, which then sends a signal cutting off voltage to the primary circuit of the ignition coil. This causes a voltage surge in the secondary, firing the spark plugs at the proper time.
PICK-UP COIL-TO-RELUCTOR AIR GAP
Normally, air gap will not need resetting unless it has been tampered with. Always use a plastic feeler gauge when checking or setting air gap. See Fig. 2. Gap must be checked at each reluctor tooth.
To check air gap, align reluctor tooth with pole piece of pick-up coil. Insert proper plastic feeler gauge. On XJS, set air gap at.007-.015" (.18-.38 mm). Check gap at each reluctor tooth.
To adjust air gap, loosen pick-up coil mounting screws. Align reluctor tooth with pole piece of pick-up coil. Insert proper feeler gauge and move pick-up coil against gauge. Tighten mounting screws.
Sunday, January 10th, 2010 AT 5:52 AM