Ignition System - Nippondenso Electronic Toyota Tercel L20

DESCRIPTION

Nippondenso electronic ignition system includes a breakerless distributor, an ignitor, an ignition coil, and pick-up coil. Distributor consists of a housing, rotor, and cap. It contains a reluctor, breaker plate, and pick-up coil assembly. (Scheme 1)

Some Toyota models have ignitor and ignition coil inside distributor. On other models, transistorized ignitor is mounted on ignition coil housing.

Both systems use a computer to control spark advance. All other distributor models contain conventional centrifugal and vacuum advance mechanisms.

Exploded View of Toyota Distributor. Scheme 1

OPERATION

On ESA and I-TEC systems, the Electronic Control Unit (ECU) is pre-programmed with data for optimum ignition timing under any engine operating condition. Using data from engine sensors (RPM, engine temperature, etc.) the ECU triggers ignition system to provide a spark at precisely the right instant. (Scheme 2)

On all others, as distributor shaft turns reluctor, reluctor teeth (one for each engine cylinder) pass magnetic pick-up coil assembly. As air gap changes with approach and pass of each reluctor tooth, magnetic field varies. This creates a signal in pick-up coil assembly.

Ignitor senses this signal, and turns ignition coil primary circuit on and off. This causes magnetic field in coil primary circuit to build and collapse, resulting in a voltage surge in secondary, which fires the spark plugs.

Schematic of Toyota ESA Ignition System Circuit. Scheme 2

AIR GAP

1. Using a flat, non-magnetic feeler gauge, check air gap between pick-up coil pole piece and each reluctor tooth. (Scheme 3) Gaps should be equal and within specification. Pick-up coil air gap should be.008-.016" (.2-.4 mm).
2. If not, loosen screws, and adjust air gap to specification. Tighten screws, and recheck air gap.

Checking Signal Reluctor-to-Pick-Up Coil Air Gap Use flat, non-magnetic feeler gauge to check clearance. Scheme 3

PRELIMINARY INSPECTION

The following precautions should be observed while servicing or testing a Nippondenso ignition system.

1. Ensure all connections are correct, reverse battery polarity may damage ignitor (ignition control unit).
2. DO NOT disconnect battery while engine is running or transistors may be damaged.
3. If a tachometer is connected to system, connect tachometer positive lead to coil negative terminal.
4. Use care when checking systems, as variations may occur between models. Connectors and wire colors also may vary.

IGNITION COIL RESISTANCE TESTS

Note. All resistance tests should be made with ignition off. If resistance is not within specification, replace ignition coil.

Primary Coil Resistance

Isolate coil from remainder of system. Connect ohmmeter, set in X1 range, between coil positive and negative primary terminals. See IGNITION COIL RESISTANCE table.

Secondary Coil Resistance

With coil isolated from system, set ohmmeter to x100 range. Connect leads to coil positive terminal and to coil tower (high tension terminal). See IGNITION COIL RESISTANCE table.

Insulation Resistance

Connect ohmmeter leads to coil positive terminal and coil mounting bracket. Reading on all models should exceed 10 megaohms (infinity).

IGNITION COIL RESISTANCE (OHMS)

IGNITION WIRE RESISTANCE

1. Set ohmmeter to x1000 range and attach leads to each end of high tension wire.
2. On all models, resistance should not exceed 25,000 ohms per wire. If it does, replace wires.

PICK-UP COIL (SIGNAL GENERATOR) RESISTANCE TEST

1. On RWD Corolla with 4A-GE engine, measure signal generator resistance between terminal "G+" and "G-", and between terminal "Ne" and "G-". (Scheme 4) If readings are incorrect, replace distributor.
2. On all other models, measure pick-up coil resistance at Pink and White wire terminals. See «PICK-UP COIL RESISTANCE»(/toyota/tercel/l20-1982-1988/remont/ignition-system/#ignition-system-nippondenso-electronic) table. If readings are incorrect, replace pick-up coil.

PICK-UP COIL RESISTANCE

Checking Toyota Pick-Up Coil Resistance. Scheme 4

IGNITOR MODULE TEST

1. Turn ignition on. Connect voltmeter negative lead to ground and positive lead to ignition coil positive terminal. (Scheme 5) Voltage reading should be 12 volts.
2. With negative lead still attached to ground, connect voltmeter positive lead to ignition coil negative terminal. (Scheme 5) Voltage reading should be 12 volts. Unplug wiring harness connector from distributor.
3. Using a 1.5-volt dry cell battery, connect battery positive pole to Pink wire terminal. (Scheme 5) Connect battery negative pole to White wire terminal. DO NOT apply voltage for more than 5 seconds. NOTE: On RWD Corolla with 4A-EG engine, use two 1.5 volt batteries in series (3-volts) when testing ignitor.
4. Voltage at coil negative terminal should be as indicated in «IGNITOR TEST VOLTAGE SPECIFICATIONS»(/toyota/tercel/l20-1982-1988/remont/ignition-system/#ignition-system-nippondenso-electronic) table. If not, replace ignitor.

IGNITOR TEST VOLTAGE SPECIFICATIONS

Testing Toyota Ignitor Module Check voltage at both positive and negative coil terminals. Scheme 5

DISASSEMBLY

1. Remove distributor cap, rotor, ignitor and ignition coil dust covers. Note position of ignition coil wiring, then disconnect from terminals. Remove 4 screws and ignition coil.
2. Remove wiring and condenser. Note position of wires on igniter, then disconnect wires. Remove 2 screws and igniter. Using 2 screwdrivers, carefully pry off set spring and reluctor. (Scheme 1)
3. Remove vacuum advance diaphragm screw. Disconnect vacuum advance link from breaker plate link, then pull advance unit off. Remove 2 screws, washers, and breaker plate assembly.
4. Remove centrifugal advance springs. Remove grease plug and screw on top of rotor shaft. Pull out rotor shaft. Remove "E" clip and centrifugal advance weights.

Note. If distributor shaft bearing is worn, replace distributor housing and shaft assembly.

REASSEMBLY

To assemble, reverse disassembly procedure. Lubricate rotor shaft with high-temperature grease. Install rotor shaft and fill cavity with grease. Secure pick-up coil wires in clips, leaving slack on pick-up coil side. Check and adjust air gap.

See also:
• IGNITION COIL RESISTANCE