How To Use a Timing Light

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You love your vehicle! And you want to ensure that it’s always running as it should. When timing is neglected, so much can suffer — you may get poor gas mileage and have less power overall. So let’s focus on how to use a timing light to keep your vehicle at optimal performance. But before we get to that, there are some basic things you should know about the timing light and the vehicle engine.

What Is a Timing Light?

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The timing light helps to properly set the timing in your vehicle. If your vehicle is from the early 90s and later, this is one step you can avoid. Any model developed within the last 20 years has a computer that does this automatically. So a scan tool rather than a timing light would work for those vehicles.

How Does a Timing Light Work?

Vehicle engines work because small explosions of gasoline make pistons move, and they go up and down. When it makes that motion, the engine is spun, and this causes the wheels to spin and the gears to rotate. For the gasoline to ignite, electric spark plugs need to be used. And those spark plug fires need to happen at the best possible time. Specifically, this needs to happen when the “top dead center” is reached. 

So it’s always a good idea to check your vehicle’s full timing range to know that everything is working as it should, to avoid problems that could occur later.

Reaching Top Dead Center

An engine goes through four steps or strokes in rapid succession to keep it running: (1) intake, (2) compression, (3) power, and (4) exhaust. These processes need to happen to reach the “top dead center” which is the specific time the spark plug needs to fire. The piston will then apply pressure to the air-fuel mixture. This is called the compression stage. Pressure is important to get a good explosion rather than a slow burn. You want the piston to be as high as possible. When this happens, the air is fully compressed, and that is also the point of the top dead center. This is the exact time you want the spark plug to fire.

Now for the power and exhaust stages. The explosion of gasoline will forcefully push the piston back down so it can rotate the engine. When this happens, you know you have power. Exhaustion occurs where the explosion’s byproducts are ejected. This makes its way to start the process. Air and fuel are drawn into the cylinder for combustion during intake. 

How To Use a Timing Light?

So, we understand that older model vehicles need to have their timing adjusted from time to time to ensure good overall vehicle performance. And we also understand that the timing light is the tool that allows you to make those necessary adjustments to the timing of the vehicle. Now, let’s look at how we would actually use the timing light to make the necessary adjustments.

1. Read the Instructions

Hook up your timing light according to your owner’s manual. Refer to the manual throughout. Make sure the vehicle is turned off and the key is not in the ignition.

2. Connect the Clips Properly

There are three clips. The red clip needs to be clamped to the positive terminal of your car battery. The black clip needs to be clamped to the negative terminal of your car battery. The third and largest clip goes on the #1 spark plug wire. Failure to do these properly can cause the whole exercise to fail.

3. Rotate the Lower Crankshaft Pulley

Next, the lower crankshaft pulley will need to be rotated so the timing marks are called out on the crankshaft pulley. Your auto manual should have what your timing degree should be.

4. Mark the Timing Marks

You have the option to use chalk to mark the timing marks. This will help make them more visible

5. Check To See if Vehicle Is Properly Idling

Start the engine, letting it warm up to see if it is idling properly. 

6. Aim Timing Light at Timing Marks

Aim the timing light at the timing marks by pressing the button on the light. Adjust the timing only if the pointer is not at the right mark.

7. Adjust the Timing Below the Distributor

Adjust the timing below the distributor, at the base of your distributor shaft. Loosen the fastener so the distributor can turn on the shaft. 

8. Rotate Distributor, Aim Timing Light Back at the Timing Marks

If the pointer is good, good. If not, continue to adjust until the pointer hits the mark. 

9. Finish Up

Once the timing is good, you know you’re almost done. Tighten the fastener for the distributor again. Turn the engine off, take the key out of the ignition, and disconnect the timing light.


In summary, it’s important to check the timing to ensure the spark plug is firing when the fuel mixture is fully compressed. This gives the ignition power. When the plugs are worn, they will fire too late or too soon. This is why timing maintenance on your vehicle is so important.

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