Ignition System - Nippondenso Electronic Toyota MR2 W10

DESCRIPTION

The Nippondenso electronic ignition system consists of a breakerless distributor, an ignition module, a pick-up coil, ignition coil, and related wiring. Distributor contains a reluctor, breaker plate, and pick-up coil assembly.

Most Toyota models have ignition coil and ignition module mounted on distributor. On Land Cruiser, transistorized ignition module is mounted on ignition coil housing.

Toyota Celica, Cressida, Supra, MR2, Van, Pickup and 4Runner models use Electronic Spark Advance (ESA). The ESA system uses a computer to control ignition timing. All other models contain conventional centrifugal and vacuum advance mechanisms.

OPERATION

On ESA system, the Electronic Control Unit (ECU) is preprogrammed 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 1)

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

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

Toyota Cressida ESA Ignition System Circuit Circuit on other models is similar. Scheme 1

AIR GAP

1. Using a flat, non-magnetic feeler gauge, check air gap between pick-up coil and reluctor. (Scheme 2) Air gap should be within.008-.016" (.20-.40 mm).
2. If air gap is incorrect, remove ignition coil (if equipped) and replace distributor assembly. On Corolla 4A-C engine, Land Cruiser, Tercel, Pickup and 4Runner 22R engine, replace pick-up coil/breaker plate assembly.

Note. On Supra 7M-GTE engine, measure air gap between pick-up coil and camshaft position sensor. If air gap is incorrect, replace camshaft position sensor.

Checking Pick-Up Coil Air Gap. Scheme 2

SPARK TEST - COROLLA, TERCEL, VAN & MR2

1. Check ignition coil and distributor connections. On MR2 and Corolla 4A-GE engine, disconnect ignition coil wire from distributor and hold wire about 1/2" away from ground. On all other models, remove spark plugs and spark plug wires. Attach spark plugs to wires and ground plugs.
2. Crank engine and check for sparks. If sparks occur, check for other source of starting problem. If no sparks occur, remove distributor cap and check ignition wire resistance. If wires are okay, go to next step. If not, replace wires as required.
3. Place ignition switch in "ON" position. Check for voltage at ignition coil positive terminal. If voltage is present, go to next step. If not, check wiring between ignition switch, coil, and ignition module.
4. Check ignition coil resistance. See «IGNITION COIL RESISTANCE TESTS»(/toyota/mr2/w10-1984-1990/remont/ignition-system/#ignition-system-nippondenso-electronic) in this article. If coil resistance is correct, go to next step. If not, replace ignition coil.
5. Check pick-up coil resistance. See «PICK-UP COIL RESISTANCE TEST»(/toyota/mr2/w10-1984-1990/remont/ignition-system/#ignition-system-nippondenso-electronic__pick-up-coil-resistance-test) in this article. If resistance is correct, go to next step. If not, remove coil and replace distributor assembly. On Corolla 4A-C engine and Tercel, replace pick-up coil/breaker plate assembly.
6. Check air gap between reluctor and pick-up coil. If air gap is correct, replace ignition module. If air gap is incorrect, remove coil and replace distributor assembly. On Corolla 4A-C engine and Tercel, replace pick-up coil/breaker plate assembly.

SPARK TEST - CAMRY, CELICA, CRESSIDA, PICKUP, SUPRA 7M-GE ENGINE & 4RUNNER

1. Check ignition coil and distributor connections. On Celica 3S-FE engine, remove spark plugs and spark plug wires. Attach spark plugs to wires and ground plugs. On all other models, disconnect ignition coil wire from distributor and hold wire about 1/2" away from ground.
2. Crank engine and check for spark. If sparks occur, check for other source of starting problem. If no sparks occur, remove distributor cap and check ignition wire resistance. If wires are okay, go to next step. If not, replace wires as required. NOTE: To prevent gasoline from being sprayed from injectors, crank engine for no more than 2 seconds at a time.
3. Place ignition switch in "ON" position. Check for voltage at ignition coil positive terminal. If voltage is present, go to next step. If not, check wiring between ignition switch, coil, and ignition module.
4. Check ignition coil resistance. See «IGNITION COIL RESISTANCE TESTS»(/toyota/mr2/w10-1984-1990/remont/ignition-system/#ignition-system-nippondenso-electronic) in this article. If coil resistance is correct, go to next step. If not, replace ignition coil.
5. Check pick-up coil resistance. See «PICK-UP COIL RESISTANCE TEST»(/toyota/mr2/w10-1984-1990/remont/ignition-system/#ignition-system-nippondenso-electronic__pick-up-coil-resistance-test) in this article. If resistance is correct, go to next step. If not, remove coil and replace distributor assembly.
6. Check air gap between reluctor and pick-up coil. If air gap is incorrect, remove coil and replace distributor assembly. If air gap is correct, replace ignition module (Celica 3S-FE engine only). On all other models, go to next step.
7. Check for "IGt" ignition signal from ECU at ignition module. If reading is about one volt, replace ignition module. If not, check power and ground wiring to ECU. (Scheme 3)and (Scheme 4). Check wiring between ECU, distributor, and ignition module. If wiring is okay, replace ECU.

Scheme 3

Scheme 4

SPARK TEST - LAND CRUISER

1. Check fuses and fusible links. Check ignition coil and distributor connections. Disconnect ignition coil wire from distributor and hold wire about 1/2" away from ground.
2. Crank engine and check for spark. If sparks occur, check for other source of starting problem. If no sparks occur, check ignition wire resistance. If wires are okay, check ignition coil and ignition module. If not, replace wires as required.

SPARK TEST - SUPRA 7M-GTE ENGINE

1. Remove duct between air cleaner and intake plenum air connector. Disconnect cruise control, accelerator, and throttle cable (automatic transmission only).
2. Remove 6 hoses from idle speed control pipe. Remove 2 bolts and idle speed control pipe from intake plenum air connector. Remove oxygen sensor wire from clamp. Disconnect hose from PCV pipe. Remove 2 bolts and disconnect PCV pipe with hoses from cylinder heads covers and throttle body.
3. Disconnect hose from intake plenum air connector. Remove 2 bolts, loosen clamps, and remove intake plenum air connector. Remove oil filler cap, 5 nuts, and "TOYOTA TURBO" labeled ignition coil cover.
4. Remove nut and disconnect No. 1 and No. 2 wires from ignition coil and clamp. Remove ignition coil, bracket, and spark plug wires. Remove No. 1 and No. 2 wires from spark plugs.
5. Remove all spark plugs. Install oil filter cap. Remove spark plugs and spark plug wires. Attach spark plugs to wires and ground plugs. Disconnect solenoid resistor and cold start injector connector. Crank engine and check for spark.

Primary Coil Resistance

Isolate coil from remainder of system. Measure resistance between coil positive and negative terminals. See IGNITION COIL RESISTANCE table.

Secondary Coil Resistance

Isolate coil from remainder of system. Measure resistance between coil positive terminal and to coil tower. See IGNITION COIL RESISTANCE table.

Coil Insulation Resistance

Isolate coil from remainder of system. Measure resistance between ignition coil positive terminal and distributor housing. Reading should exceed 10 megaohms (infinity).

IGNITION COIL RESISTANCE - OHMS

IGNITION WIRE RESISTANCE TEST - CELICA & SUPRA

1. On Celica 3S-FE engine, measure pick-up coil resistance between terminals "G" and "G(-)", and between "NE" and "G(-)". (Scheme 5) Resistance should be 140-180 ohms. If resistance is incorrect, remove ignition coil and replace distributor assembly.
2. On Celica 3S-GE engine and Supra, measure pick-up coil resistance between terminals "G1" and "G(-)", between "G2" and "G(-)", and between "NE" and "G(-)". (Scheme 5) Resistance should be 140-180 ohms. If resistance is incorrect, replace distributor assembly.

Toyota Celica & Supra Pick-Up Coil Resistance Test. Scheme 5

PICK-UP COIL RESISTANCE TEST

1. On Camry and Cressida, measure pick-up coil resistance between terminals "G" and "G(-)", and between "NE" and "G(-)". On Corolla 4A-GE engine and MR2, measure pick-up coil resistance between terminals "G(+)" and "G(-)", and between "NE(+)" and "NE(-)". (Scheme 6)
2. On Pickup, Van, and 4Runner, measure pick-up coil resistance at distributor connector. (Scheme 6) On Corolla 4A-C engine and Tercel, measure pick-up coil resistance at ignition module terminals.
3. If resistance is incorrect, replace pick-up coil/breaker plate assembly on Corolla 4A-C engine and Tercel. Remove ignition coil (if equipped) and replace distributor assembly on all other models.

PICK-UP COIL RESISTANCE - OHMS

Toyota Pick-Up Coil Resistance Test (All Models Except Celica, Land Cruiser & Supra). Scheme 6

IGNITION MODULE TEST - LAND CRUISER

1. Turn ignition switch to the "ON" position. Connect voltmeter positive lead to ignition coil positive terminal and ground voltmeter negative lead on ignition module body. Voltmeter reading should be about 12 volts.
2. Connect voltmeter positive lead to ignition coil negative terminal and ground voltmeter negative lead on ignition module body. Voltmeter reading should be about 12 volts.
3. Unplug distributor connector. Using a flashlight (1.5 volt) battery, connect positive pole to Pink wire terminal and negative pole to White wire terminal. DO NOT leave battery connected for more than 5 seconds.
4. Connect voltmeter positive lead to ignition coil negative terminal and ground voltmeter negative lead on ignition module body. Voltmeter reading should be 5 volts less than battery voltage.

IGNITION MODULE TEST - SUPRA 7M-GTE ENGINE

1. Disconnect ignition module 6-pin connector, module is located next to alternator. Turn ignition switch to the "ON" position. Check for battery voltage between terminal No. 3 and ground. (Scheme 7)
2. If voltage is present, turn ignition off. Plug in ignition module 6-pin connector and unplug ignition module 4-pin connector. Disconnect each ignition coil from its connector.
3. Turn ignition switch to the "ON" position. Connect an ohmmeter between terminal No. 2 of third ignition coil and ground. Using 2 flashlight (1.5 volt) batteries, apply 3 volts to terminal No. 2 of 4-pin connector. (Scheme 7) With 3 volts applied, check that ohmmeter indicates momentary continuity.
4. Connect an ohmmeter between terminal No. 2 of first ignition coil and ground. Apply 3 volts to terminal No. 4 of 4-pin connector. (Scheme 7) With 3 volts applied, check that ohmmeter indicates momentary continuity.
5. Connect an ohmmeter between terminal No. 2 of second ignition coil and ground. Apply 3 volts to terminal No. 3 of 4-pin connector. (Scheme 7) With 3 volts applied, check that ohmmeter indicates momentary continuity.

Supra 7M-GTE Engine Ignition Module Test. Scheme 7

ENGINE CRANKS BUT WILL NOT START

Check for faulty spark plug(s), ignition coil, ignition module, distributor, camshaft position sensor (Supra 7M-GTE engine), and ignition system wiring. Repair or replace parts as necessary. Check ignition timing and adjust if necessary.

HESITATION & POOR ACCELERATION

Check for faulty spark plug(s) and ignition system wiring. Repair or replace parts as necessary. Check ignition timing and adjust if necessary.

ROUGH IDLE, STALLS

Check for faulty spark plug(s), ignition coil, ignition module, distributor, camshaft position sensor (Supra 7M-GTE engine only), and ignition system wiring. Repair or replace parts as necessary. Check ignition timing and adjust if necessary.

Exploded View of Toyota Distributor. Scheme 8

Note. Distributors on Celica, Cressida, Corolla 4A-GE engine, MR2, and Supra 7M-GE engine, Pickup and 4Runner 22R-E and 22R-TE engines are not serviceable and must be replaced as an assembly.

REASSEMBLY

Note. Reassembly information not available from manufacturer.

See also:
• IGNITION COIL RESISTANCE TESTS
• PICK-UP COIL RESISTANCE TEST