See Figure 1
SECONDARY SPARK TEST
See Figure 2
This procedure is performed best with a spark tester. Two types of spark testers are commonly available; both available from most auto parts stores. The neon bulb type is connected to the spark plug wire and flashes with each ignition pulse. The air gap type must be adjusted to match the spark plug gap required for the engine. This type will allow you to see the condition of the spark as well as checking for spark itself. If the spark is orange/yellow, this indicates a weak spark; blue would be a strong spark.
- Disconnect a spark plug wire, and install the spark tester.
- Ground the tester at a good location on the engine.
- Crank the engine and check for spark at the tester.
- If spark occurs at the tester, the ignition system is functioning properly.
- If there is no spark at the tester, remove the distributor cap and verify the rotor is turning when the engine is cranked.
- If the rotor is turning, check for spark at the ignition coil by installing the tester in the coil wire.
- If no spark exists, test the ignition coil, power transistor and related wiring.