How Does a Timing Light Work?

After talking about the electronic ignition and explaining how to mount it, Classic Auto Elec tells us more about the timing light.

What is the use of a timing light?

The lamp helps stall the ignition of your vehicle (gasoline). Improper ignition timing can have a negative impact on your engines, such as premature wear and even engine breakage, for example, by drilling a piston.

On gasoline engines, spark plugs are used to ignite a mixture of air and gasoline in the engine cylinders. Each spark plug fires a little before the piston reaches the top of its compression stroke. Thus, the mixture of air and gasoline can burn entirely before the start of the combustion stroke.

In the event of a wrong engine stall, the performance and engine consumption may be degraded. The exhaust gases emitted then contain a much too large proportion of hydrocarbons, the mixture is not entirely burned.

How does timing light work?

A timing light is a trigger gun that operates a burst tube, coupled with an inductive clamp. This clip must be in place on a candle wire for the gun to work properly.

The sensor must be on the spark plug wire of cylinder 1, arrow pointing towards the spark plug. Warning: this sensor is fragile!

The lamp must also be connected to the car battery, red to +, black to -. Be careful, though; the device only works on 12 Volt batteries. For 6 Volts batteries, an auxiliary battery will be required.

For a standard model, once connected to the candle, a synchronized flash occurs with the spark of the candle. The flash locks the igniter relative to a mark on the crankshaft pulley or the flywheel. The strobe flash will then give the impression of “freezing” the pulley. We will then see the mark as if the pulley was stopped since the lamp will flash at the same frequency as turns the pulley.

The different types of timing lights

• The standard timing light: it produces the flash when the candle sparkles. It makes it possible to precisely adjust the exact ignition point of the candle concerning the Top Dead Center. To adjust the ignition advance, it requires the presence of advance timing marks other than the pure mark of PMH, which is not the case on all cars.
• The phase-shifted strobe lamp: it is equipped in addition to a self-powered flash tube, independent of the spark plug, and a phased electronic circuit. It is, therefore, possible to adjust, using a knob on the gun, the value in degrees of the ignition advance (see photo) that you want. The flash will be triggered by some delay compared to the ignition of the candle so that it will be out of phase. This uses the fixed marker and the TDC mark (on the crankshaft pulley or the flywheel): the two markers must be in front of the flash for the adjustment to be good. It thus makes it possible to very merely regulate the advance with the ignition, without the need for additional marks on the vehicle. Therefore, if you want to make the changes presented in your vehicle, we strongly advise you to get closer to a professional car mechanic.

We remind you that all parts and accessories marketed by ORECA are elements intended for motor racing. Thus, the use of these parts and accessories on a vehicle of general use not designed for motor racing can:

• Make your vehicle unfit for open road traffic and make it non-compliant with the provisions of the Highway Traffic Act.
• Make the vehicle non-compliant with its homologation certificate.
• Cancel the manufacturer’s warranties from which the vehicle could benefit
• Cancel the insurance cover initially subscribed for the vehicle

Safety reminders for any use

The timing light only works when the vehicle is running. You will suspect that we must, therefore, respect basic safety rules.

• Avoid wearing loose clothing as they can be caught in moving parts of the motor. 
• Pay attention to moving motor parts (pulleys, belts …) or hot (exhaust …). 
• The vehicle must be on a flat surface, and the parking brake pulled. 
• Once the calibration is done, it is necessary to shut down the engine before any intervention. 
• Also, pay attention to the cords of the measuring devices. 
• Do not use the timing light in wet weather.