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Mazda RX7. Manual - part 12

IGNITION SYSTEM

Article Text

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 03:31PM

ARTICLE BEGINNING

1983 Distributors & Ignition Systems
MITSUBISHI ELECTRONIC IGNITION - MAZDA ROTARY ENGINE

Mazda RX7

DESCRIPTION

The Mitsubishi electronic ignition system, used on the Mazda
RX7 rotary engine, is unique in that it has 2 sets of spark plugs
(leading and trailing). There is one set in the front rotor housing
and one in the rear rotor housing. See Fig. 1. There are also 2
ignition coils, 2 pick-up coils located in the distributor, and 2
coil-to-distributor high tension wires.

Fig. 1: Schematic of RX7 Ignition System

There are 2 separate igniters, mounted externally on the
distributor housing. One is for the leading side and the other for
the trailing side. Other system components include a battery,
ignition switch, ignition control switches, (water temperature,
altitude, etc.), and various relays.
All models are equipped with an ignition control system and
centrifugal advance mechanisms. All models have vacuum control units
for both leading and trailing sides.

OPERATION

A reluctor (signal rotor) is mounted on the reluctor (rotor)
shaft. It turns inside 2 magnetic pick-up coils, one for the leading
side and one for the trailing side. See Fig. 2.
As each tooth of the reluctor approaches and then passes the
leading pick-up coil, a signal is generated. It is sent to the leading
ignitor, which breaks the primary circuit in the leading ignition
coil.

IGNITION SYSTEM

Article Text (p. 2)

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 03:31PM

As each tooth passes the leading pick-up coil, the previous
passing tooth approaches and becomes aligned with the trailing pick-up
coil. This triggers a signal to the trailing ignitor, which breaks the
primary circuit in the trailing ignition coil.
Therefore, immediately after the leading spark plug fires,
the trailing spark plug also fires, providing more complete and
efficient combustion while reducing HC and CO emissions.
As the primary circuit is broken in the leading and trailing
ignition coils, a voltage surge occurs in the secondary circuit of
the ignition coils. This high voltage is transmitted through the
leading and trailing high tension wires to the distributor, rotor and
spark plugs.
An emission control unit is also included in the ignition
control system, along with different sensing switches to provide
proper timing under varying engine operating conditions.

ADJUSTMENTS

RELUCTOR-TO-PICK-UP COIL AIR GAP

1) Remove distributor cap and rotor. Turn distributor shaft
until the extended tooth of the reluctor (signal rotor) aligns with
core of pick-up coil. See Fig. 2.
2) Using a feeler gauge, check for .020-.035" (.5-.9 mm) air
gap. If gap is incorrect, replace pick-up coil and bearing assembly
or distributor drive shaft, if necessary.

Fig. 2: Adjusting Distributor Air Gap
Check air gap at all teeth and both pick-up coils.

IGNITION TIMING

1) To adjust leading timing, loosen distributor lock nut,
and rotate distributor housing until correct timing is obtained. See

IGNITION SYSTEM

Article Text (p. 3)

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 03:31PM

Fig. 3.

2) To adjust trailing timing, loosen the screws securing the
trailing vacuum unit. Move the vacuum unit outward (to advance) or
inward (to retard). Retighten screws when correct timing is obtained.

Fig. 3: Adjusting Ignition Timing
Distributor position determines leading time. Vacuum unit position
adjusts trailing timing.

TESTING

HIGH TENSION WIRE RESISTANCE CHECK

Turn ignition switch "OFF". Connect ohmmeter leads to each
end of coil-to-distributor high tension wire. Resistance should not
exceed 16,000 ohms (plus or minus 400 ohms) per 39.37" (1 m).

IGNITION COIL RESISTANCE CHECK

Set an ohmmeter in the low scale. With ignition switch
turned "OFF", and coil wires disconnected, attach ohmmeter leads to
primary terminals of leading coil and then trailing coil. Primary
resistance should be 1.22-1.48 ohms for each ignition coil.

PICK-UP COIL RESISTANCE CHECK

1) Set an ohmmeter in the x100 scale. Turn ignition switch
"OFF". Disconnect connector between ignitor and distributor. See
Fig. 4.

IGNITION SYSTEM

Article Text (p. 4)

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 03:31PM

Fig. 4: Ohmmeter Hookup for Pick-Up Coil Resistance Check
Replace pick-up coil and bearing plate assembly if reading is not
600-700 ohms.

2) Connect ohmmeter leads to leading terminals and then
to trailing terminals. Resistance should be 600-700 ohms at 68

(20

C) for each set of pick-up coils. If not, replace pick-up coil

and bearing assembly.

PICK-UP COIL OPERATION CHECK

1) With distributor connector still disconnected, touch
ammeter leads to leading terminals and then to trailing terminals.
2) Place a screwdriver against core of pick-up coil being
tested. Indicator of meter should move each time screwdriver is taken
quickly away from core. If not, replace pick-up coil and bearing
assembly.

IGNITER CHECK

1) Remove ignitor from distributor base. Make a circuit as
shown in Fig. 5 using wire and a test bulb. Use a 12 volt bulb of
less than 10 watts.

Fig. 5: Test Lamp Hookup for Checking Ignitor Operation
Bulbs should flash when switch is operated.

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