See Figures 1, 2 and 3
The electronic ignition system differs from the conventional breaker points system in form only; its function is exactly the same: to supply a spark to the spark plugs at precisely the right moment to ignite the compressed gas in the cylinders and create mechanical movement.
Located in the distributor, in addition to the rotor cap, is a spoked reluctor which fits on the distributor shaft where the breaker points cam is found on non-electronic ignitions. The reluctor revolves with the rotor head, as it passes a pickup coil inside the distributor body it breaks a high flux field, which occurs in the space between the reluctor and the pickup coil. The breaking of the field allows current to flow to the pickup coil. Primary ignition current is then cut off by the electronic ignition unit, allowing the magnetic field in the ignition coil to collapse, creating the spark which the distributor passes on to the spark plug.
There are 4 different types of distributors used with electronic ignition systems. A single post pickup coil with a transistorized ignition unit, a ring-type pickup coil with an Integrated Circuit (IC) ignition unit, an IC ignition unit without a pickup coil, and a crank angle sensor are the main variations in the distributors used for these systems.
Because no points or condenser are used, and because dwell is determined by the electronic unit, no adjustments are necessary. Ignition timing is generally checked in the usual way (be careful to check for slight variations depending on model and engine), but unless the distributor is disturbed it is not likely to ever change very much.
Service consists of inspection of the distributor cap, rotor, and ignition wires, replacing when necessary. These parts can be expected to last at least 40,000 miles (64,400 km). In addition, the reluctor air gap should be checked periodically.
The 1983 Pulsar for the 49 states, as well as the California and Canada models used no pickup coil for the electronic ignition system; on these models, the IC ignition unit is mounted on the inside of the distributor. The 1984-86 Pulsar for California and non-turbocharged Canadian models use no pickup coil for the electronic ignition system; on these models, the IC ignition unit is mounted on the inside of the distributor housing.
The 1984-88 (E16 engine only) for the 49 states, the 1987-88 California and Canada models (E16 engine only) and the turbocharged version of the Pulsar use a crank angle sensor. This sensor monitors engine speed and piston position and sends to the computer signals on which the controls of the fuel injection, ignition timing and other functions are based.
The Pulsar CA16DE and CA18DE engines do not utilize a conventional distributor and high tension wires. Instead they use 4 small ignition coils fitted directly to each spark plug, and a crank angle sensor is mounted in the front timing belt cover.
The 1982-86 IC ignition system uses a ring-type pickup coil which surrounds the reluctor instead of the single post type pickup coil on earlier models.
1987-96 Sentra models are equipped with a different means of generating the distributor signal. The reluctor and pickup coil are replaced by a rotor plate and crank angle sensor. The rotor plate is machined with slits that break and then restore a beam of light (a light emitting diode is situated above the plate and a photo-sensitive diode is located underneath). There are 360 slits in the plate to generate an engine speed signal and 4 slits to generate 180° crank angle signals.
When the slits in the rotor plate break and then restore the beam of light, the photo diode generates rough pulses. Then, a wave forming circuit located in the base of the distributor converts these pulses to clear on-off pulses. The Electronic Control Unit, a microcomputer, then utilizes these signals, in combination with others, to generate the actual on-off signal that controls the ignition coil and fires the ignition.
Service on electronic ignition systems consists of inspection of the distributor cap, rotor and ignition wires, and replacing them when necessary. Check the ignition wires for cracking of exterior insulation and for a proper fit on the distributor cap and spark plugs. These parts can be expected to last for at least 40,000 miles (64,400 km), but you should inspect these parts every 2 years or 30,000 miles (48,300 km). In addition, the reluctor air gap should be checked periodically if the system has no crank angle sensor.