How to Use A Timing Light to Set Your Ignition Timing

Understanding ignition timing:

How to use timing light to set ignition timing
How to use timing light

Before learning what ignition timing is and how to use a timing light, we need to learn how engines work in general. Your engine is a symphony of parts moving rapidly – rods, pistons, crankshaft, camshafts, pulleys, and valves – all these heavy pieces moving with quick velocity in your engine. 

They work by using some explosions of gasoline to enable pistons move up and down. The motion it generates make engines spin, which in turn makes the gears rotate and the wheels spin. The valves move in and out, the pistons move up and down, the crankshafts spin widely at the center of everything and the connecting rods push and pull. This complex symphony comes into play anytime you drive your car down the street.

The timing of a car is the process whereby the spark plugs fire and creates a spark in the combustion chamber of the car. In order for your car to perform properly, your timing has to be at the right setting. It is possible for you to adjust the timing of your car by using timing light and a set of tools or impact wrench. Generally, there are two types of timing every engine can have. It can either be cam timing or ignition timing. 

Does your car need to be adjusted?

You will not need to adjust the timing of modern cars that have electronic ignitions, but 4-stroke engines that are old style will require their timing adjusted regularly for their engines to function efficiently, ensuring that the spark fires at the right time in the ignition cycle.

Understanding ignition cycle:

The 4-cycle engine
The spark plug fires and creates a combustion that forces the piston down the cylinder.

The 4-cycle engine has four strokes which include the process of intake, compression, power and exhaust. The timing of the ignition is the period when the spark plug fires and creates a combustion that forces the piston down the cylinder, which is the point between compression and power.

How to use timing light to set ignition timing:

Engine ignition sytem.

In order to maintain the best performance of your car, you need to set the ignition timing, particularly for older models. When the timing is ignored, it can result to poor gas mileage, less power, and other problems that can hinder the engine from running. 

Though you can get a mechanic to set the ignition timing for you, it is an easy process that you can do on your own. Before you proceed, check your vehicle to see if it requires this maintenance.

Step 1: Set up the timing light:

Make sure the engine is turned off and remove the key from the ignition to avoid accidents. 

Step 2: Set up the battery:

Ensure the battery terminals are clean to enable a good connection. Otherwise, clean then properly while being cautious as to avoid contact with your skin, because battery acid is hazardous. If contact happens, use soap and water to wash.

Step 3: Connecting the clamps:

The timing light comes with some clamps or plugs. Attach the corresponding cables to the right power source – the red clip to the positive terminal of the car’s battery and the black clip to the negative terminal. The biggest clip having the thickest insulation goes to the first spark plug wire. Make sure you attach the right plug, as this will impact the timing readings.

Step 4: Rotate the crankshaft:

The next process will require you to rotate the lower crankshaft pulley to make the timing marks visible. Take note that the timing marks on some vehicles are located at a different place; you should therefore check the instruction manual to see to determine the exact location.

Crankshaft  of car
Crankshaft of car

Additionally, you can use chalk to mark the timing points for them to be more visible. Then disconnect the rubber hose from the vacuum and use duct tape to seal off the end of the hose. 

Step 5: Reading the numbers:

Now, turn on the car’s ignition and allow it to idle so it can warm. Use the timing light to aim at the timing marks by pressing the button on the light. Every time the spark plug fires, it passes a current to the ignition light which creates a strobe effect as it go on and off. The marks on the flywheel will reveal a number when you shine light on the timing numbers. 

The ignition timing works using a principle which is: when the spark plug is fired up, the current tells the timing light to flash. This will effectively cause one of the timing numbers to appear as the engine runs. The number can then be compared to that of recommended by manufacturers.

How to adjust the timing:

Now that the timing number is visible, it is possible to make adjustments by following these processes:

  • Loosen the distributor bolt to the point where it can be barely twisted. This will enable the distributor rotate the shaft.
  • Slightly rotate the distributor, and then point the timing light to the timing marks. If it’s farther from the marks, rotate the distributor in the opposite direction then check again using your timing light. Do this until the pointer points at the right degree.
  • Once you are satisfied with the timing, re-tighten the bolt for the distributor, ensuring you do not remove the distributor. After it is tightened, double check your timing again because re-tightening may affect your timing.
  • Turn off your engine and remove the key from the ignition.
  • Disconnect the timing light

Effects of poor ignition timing:

Incorrect ignition timing can result to poor fuel management, slow acceleration, hard starting, pinging or backfiring. Little spark advance will lead to low power, backfiring, poor performance and bad gas mileage. High advance will result to pre-ignition and hard starting.


1. What causes bad ignition timing?

Bad ignition timing can occur when there is a problem with the ignition system. The timing has to be set according to the engine design.

2. Why is ignition timing important?

Ignition timing is important because it affects several other variables such as engine power, fuel economy, engine life and torque. 

3. Can bad timing cause hard start?

Bad ignition timing can cause hard start because the fuel and air mixture must be ignited at the right time for the engine to start. In cases of bad ignition timing, the fuel and air mixture will not be ignited at the correct time; this will cause the engine to become hard to start.

4. Will car run if timing is off?

If your timing is off, you will know because the car will not run well, that is if it runs at all. 

5. Can incorrect timing cause overheating?

If the timing is incorrect, it can cause the fuel and air mixture to ignite too soon, and in turn result to an increase in the amount of heat generated. This can make the engine overheat.

Read more: What Does the Check Engine Light Really Mean?