Ignition System - Nippondenso Chevrolet Sprint I

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.

On Sprint and Spectrum, the ignitor is mounted inside distributor.

OPERATION

On all models, 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.

AIR GAP

1. Using a flat, non-magnetic feeler gauge, check air gap between pick-up coil pole piece and each reluctor tooth. (Scheme 1) 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. On Sprint, remove ignitor module before loosening pick-up coil.

Checking Signal Reluctor-to-Pick-Up Coil Air Gap Use flat, non-magnetic feeler gauge to check clearance. Scheme 1

Spark Test

Remove any spark plug wire and hold wire about 1/4" away from ground. Crank engine and check for spark. If spark occurs, check ignition timing, spark plugs, fuel system, and engine compression. If no spark occurs, check coil primary circuit for shorts or loose connections. Check air gap. See ADJUSTMENTS .

Engine Does Not Start

1. Check distributor rotor and cap. If okay, check ignition coil resistance. If incorrect, replace ignition coil. If resistance is correct, check connections in primary and secondary circuits.
2. If coil and circuits are okay, check spark plug wires and spark plugs. If spark plugs are okay, check ignition timing. If correct, check valve timing.

Engine Misfires

Check distributor cap and rotor. Check for broken wiring and loose distributor shaft. If okay, check coil and spark plug wires. Check spark plugs for fouling, cracks or other damage.

Engine Does Not Run Smoothly

1. Ensure a normal spark pattern is generated at each cylinder. Replace spark plug wire on any cylinder with an abnormal spark. If problem still exists, replace distributor cap.
2. If spark at cylinder is normal, cause each cylinder to misfire and check for engine RPM change. If RPM changes, ignition system is okay. Temporarily replace spark plug on any cylinder that does not change RPM.

No Spark

1. Check coil and spark plug wires. Check spark plugs for fouling, cracks or other damage. Check ignitor.
2. If ignitor is okay, check distributor for broken wiring, cap and rotor. If okay, check ignition coil and ignition system primary circuit.

Ignition Failure

Perform test under ENGINE DOES NOT START undere a previous heading. If okay, check spark plug heat range. If problem still exists, check distributor advance.

Engine Knocks Regularly

Check ignition timing. Check spark plug heat range. If problem still exists, check distributor advance mechanism for broken springs or other damage.

Engine Lacks Power

Check ignition timing. Check spark plugs for fouling. If problem still exists, check distributor advance mechanism for damage.

Note. For additional trouble shooting information, refer to the TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.

TESTING

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 .

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 .

Insulation Resistance

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

IGNITION WIRE RESISTANCE

1. Set ohmmeter to x1000 range and attach leads to each end of high tension wire.
2. On Spectrum, see «IGNITION WIRE RESISTANCE»(/chevrolet/sprint/i-1984-1988/remont/ignition-system/#ignition-system-nippondenso) . On Sprint, resistance should not exceed 25,000 ohms per wire. If it does, replace wires.

Spectrum & Sprint

1. Turn ignition off. Remove distributor cap and cover. On Spectrum, disconnect Red signal generator wire from ignitor. On Sprint, disconnect Red and White wires from ignitor.
2. On both models, measure resistance across signal generator Red and White wires. On Spectrum, resistance should be 140-180 ohms. On Sprint, resistance should be 130-190 ohms.

Scheme 2

1. Disconnect coil wire from cap and hold wire about 1/4" away from ground. Turn ignition on. Connect a flashlight (1.5 volt) battery between Red (positive) and White (negative) ignitor wires.
2. Ignitor is okay if sparks are generated between coil wire and ground when one flashlight battery lead is disconnected. DO NOT apply voltage to ignitor for more than 3 seconds.
3. If no spark occurs, ensure ignition coil is energized with ignition on. Perform resistance test on ignition coil. If both tests indicate coil is normal, ignitor module is at fault.
4. On Sprint, remove distributor cap and dust cover from module. Connect ohmmeter, test lamp, and 12-volt battery to module. (Scheme 2) (Scheme 2): Testing Sprint Ignitor Module DO NOT reverse ohmmeter connections. Courtesy of General Motors
5. Set ohmmeter to x1 scale. Connect ohmmeter negative lead to Red wire terminal and positive lead to White wire terminal. Test lamp should light, indicating module is okay. If not, replace module.

Spectrum

1. Remove distributor cap. Disconnect coil wire from cap and hold wire about 1/4" away from ground. Connect a flashlight (1.5 volt) battery between Red (positive) and White (negative) ignitor wire.
2. Ignitor is okay if sparks are generated between coil wire and ground when one flashlight battery lead is disconnected. DO NOT apply voltage to ignitor for more than 3 seconds.

Note. DO NOT reverse ohmmeter connections as module will be damaged.

DISASSEMBLY

Note. Chevrolet Spectrum & Sprint distributor overhaul information not available from manufacturer.

SPECIFICATIONS

IGNITION COIL RESISTANCE

IGNITION WIRE RESISTANCE

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• ADJUSTMENTS