How to use a timing light

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A vehicle that isn't running in time will show signs of a rough idle, pinging, loss of power, or possibly a check engine light. This doesn't always mean a vehicles timing needs to be adjusted. Most modern vehicles have an electronic ignition system, which means that an internal computer adjusts the timing automatically.

The Four-Cycle Stroke of an Internal Combustion Engine

Usually, the only vehicles that need a timing adjustment are classic cars with a designated four-cycle stroke. Four-Cycle Stroke refers to the four positions a piston is in at any given time which is Intake, Compression, Combustion, and Exhaust. As the intake valve opens, air and fuel are drawn into the chamber. As the piston head moves upward, the gas and air are compressed. The spark plug fires as the piston reaches its optimal position which is combustion. The explosion forces the piston to retreat as the exhaust valve opens to allow burnt fumes to escape through the exhaust.

How to use an Innova 5568a Timing Light

Using the Innova 5568a timing light on a 1968 MGC.

Note: The 5568 and 5568a are the same timing lights and operate the same way. The only difference is the colors.

To use the Innova 5568a timing light, you can follow these steps:

Innova 5568a

Innova 5568a with Inductive Pickup

1. Prepare the vehicle: Park the vehicle on a level surface and ensure the engine is turned off. Open the hood and locate the ignition coil or distributor, depending on your vehicle's ignition system. Identify the No. 1 spark plug cable.

2. Connect the timing light:

Inductive Pickup

The Innova 5568a timing light has three connections: red for positive (+), black for negative (-), and the green adapter is only for reading dwell angle. Connect the red clip to the positive terminal of the vehicle's battery and the black clip to the negative terminal. Also, make sure the inductive pickup clamp is properly connected to the No. 1 spark plug cable and that the arrow on the clamp is pointing toward the spark plug. Ensure the connections are secure.

3. Start the engine: Start the vehicle's engine and let it idle. Make sure the transmission is in neutral or park and the parking brake is engaged. Allow the engine to reach normal operating temperature.

4. Aim the timing light: Point the timing light towards the timing marks on the harmonic balancer or flywheel/flexplate. These marks indicate the timing degrees and are usually located near the bottom of the engine, at the front or rear depending on the design. You may need to use a flashlight or mirror to locate the marks.

5. Activate the timing light: With the engine running, press the trigger or activate the timing light according to the instructions specific to the Innova 5568a model. The timing light will flash each time the spark plug fires, illuminating the timing marks.

6. Check the timing: Observe the timing marks while the timing light is flashing. The correct timing degree should align with the recommended specifications for your vehicle, which can be found in the service manual or a repair guide. Adjust the timing if necessary by loosening the distributor hold-down bolt (if applicable) and rotating the distributor slightly.

7. Retest and finalize: After making adjustments, repeat the process by activating the timing light and observing the timing marks. Ensure they align with the desired timing degree. Once the timing is set correctly, turn off the engine and disconnect the timing light.

Remember to consult your vehicle's service manual or a trusted repair guide for specific instructions and timing specifications for your particular vehicle model.

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