Timing Light - It can catch you out!

Welcome to this article that features the humble Timing Light.

This tool is often underutilized, or in some cases, it can mislead the operator, which can lead to time being wasted and misdiagnosis of particular symptoms.

First things first. If an engine has been rebuilt, or modified in any way, you should check the ignition timing. Whoever put the engine together may swear they have checked the timing, but even the "best in the business" can make mistakes.

Here's a link to a great tip when it comes to using a timing light on an engine running dual outlet ignition coils. Check it out, hopefully you won't be caught by it in the future.

What if I don't have a timing light?
You can buy a timing light, a simple one with just one on/off button or trigger, for less than $100. The amount of time it is going to save you will pay itself back many times over if you use it several times.

The timing light with the buttons and the display is great, really great, but if you can't afford one of these top-of-the-line units, you are far better off getting a simple one, than not having one at all.

My advice is - Just Get One!

So what can I check with a timing light?
First of all, you can check that the base ignition timing is set correctly.

What is the base ignition timing? It's what the vehicle manufacturer specifies the timing should be at a particular RPM (there may be other things you need to do to have the engine ready for checking, like link a particular wire in the diagnostic connector to put the ECU into a diagnostic mode). So - you can check that.

You can also check that the ignition timing is advancing as the engine speeds up. In carburetted engines, this is called mechanical advance.

You can check that the ignition timing retards when there is less vacuum (i.e. higher engine load). Using the carburetted engine as an example again, if you were to disconnect the vacuum line running from the intake manifold to the vacuum modulator on the side of the distributor, while at idle, the ignition timing should retard a little. Now, it's not going to move 30 degrees, but you should see a noticeable movement in the ignition timing.

Now, straight away you can see some very easy and quick diagnostics you can use a timing light to determine (and you don't need one of the fancy ones with the buttons and dials, etc).

I hope you have found this post useful and if you are interested where a timing light can catch out even experienced mechanics and tuners, check out this timing light link.