Ignition System Check

GENERAL INFORMATION

Warning: Observe safety precautions to avoid electric shock. Switch off the ignition before connecting test equipment. CARBURETED ENGINES WITHOUT CATALYTIC CONVERTER: Ignition faults are usually caused by contaminated contacts or flashover along the surface.

Do not check the ignition by disconnecting the high-voltage leads one at a time.

PROCEDURE

1. If the engine fails to start, first check the battery voltage while cranking by disconnecting the high-voltage lead from the coil and grounding it. If the voltage is below 9.5 V, check the battery and charging system.

2. At normal cranking speed, connect a timing light and check for spark at the plugs. If the timing light flashes, check the spark plugs. Otherwise check the condition of the wiring, distributor cap, rotor and carbon brush.

3. If there is spark, check the carburetor.

4. If there is no spark, check the voltage at the "+" terminal of the coil (11.7 V). If the voltage is below 11 V, check the entire power supply circuit, including the fuse and ground connections.

5. If the voltage is normal, check the ignition coil (winding resistance, reliability of connections, especially low-voltage ones).

6. If the coil is good, the electronic igniter is faulty (check and repair at an automotive service facility).

7. Check the thermo-vacuum valve. Disconnect the damper valve and blow through it – air should pass freely from the distributor side.

8. If the engine runs erratically, check the low-voltage and high-voltage circuits.

9. Check the reliability of the contacts and the resistance of the primary circuit.

10. Check the condition of the distributor cap, spark plugs (by swapping them), rotor and carbon brush.

11. Use a timing light to check for voltage at all spark plugs and wires.

12. If voltage is absent at some wires, check the wires or the distributor cap.

13. If there is no high voltage at all, check the ignition coil.

CARBURETOR ENGINES WITH CATALYTIC CONVERTER AND FUEL INJECTION ENGINES

PROCEDURE

1. If the ignition system fails, check the condition of the air filter, spark plugs, throttle cable adjustment, compression and valve clearances.

2. Checking the ignition system of these engines comes down to determining the ignition advance angle, checking the reliability of the connectors on the control unit and the wire attachments.

3. On fuel injection engines, use the self-diagnosis mode.

4. If the fault is not found, take the vehicle to an automotive service facility.