There are two basic kinds of timing lights — DC powered timing lights, which operate from your vehicle's battery, and AC powered timing lights, which operate on 110 volt house current. Of the two, the DC light is preferable because it produces more light to see the timing marks in bright daylight.
Regardless of what kind is used, the light normally connects in series with the No. 1 spark plug using an adapter. Models that are more expensive sometimes use an inductive pickup, which simply clamps around the plug wire and senses firing impulses. Inexpensive models use alligator clips; one clamps onto the connection between the plug and the plug wire, and the others clamp onto the vehicle battery terminals.
NOTE: Some timing lights will not work on electronic ignition systems, so unless you still own a vehicle equipped with points, check to make sure the timing light you buy will work.
The biggest problem you will probably have when using a timing light is trying to see the timing marks on the crankshaft pulley. Before you time the engine, mark the appropriate timing indicators with fluorescent paint or chalk. Stay out of direct sunlight when you time the engine and buy a timing light with a xenon light, not a neon light. Timing lights that use a xenon tube provide a much brighter flash than those that use a neon tube do.
| Fig. 1: A modern electronic timing light. Note the inductive
pick-up clamp.
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