Quick Tip: Ignition Coil Primary Voltage Test

Ignition coils can be tested in a few different ways. 

One example is a primary ignition test. 

So we're going to check the primary voltage on a coil on this Hyundai behind me. 

All right. 

So to do this, we'll use the guided component test function. 

I already had the vehicle previously ID, so I'm going to my previous vehicles and there it is right there. 

Now we'll see all the different systems we can test in this case while the coil's going to be under engine and then we'll Scroll down a little bit here and we find the ignition coil right there we go into primary tests. 

You see we have a few different tests we can do. 

In this case we're going to do a signature test, so it tells us what the connector's going to look like. 
 
It says to hook to ignition coil negative and a no good ground. 

We've already done that. 

So we'll come down here and we'll hit view meter and we'll see we have a flat line because the vehicle's not running. 

So let's start up the vehicle and look at what we have. 

That looks pretty good. 

Alright, So what we see here is the primary side of the coil. 

Now the primary and the secondary side of the coil generally mirror each other. 

This one's just a really good example of of what it should look like. 

So we see we have ignition power comes in and then when it goes to charge up the primary side of the coil, it's going to pull it down to ground. 

So we should have roughly 0 or a little bit higher, but that would be what we, what we call dwell, right? 

So that's where it's going to go and charge up the coil. 

Then we have our firing line so we can see what that looks like. 

We have a nice high firing line right there. 

It's about 100 volts in this case. 

Primary side, it's going to be a lot lower than the secondary side of being 10s of thousands of volts. 

But measuring on the primary side, like I said, it looks pretty similar. 

Then we have our sparkline, which is the actual burning inside the cylinder. 

There we can see how long it lasts. 

We can see whether or not it's running rich or running lean. 

If it was running lean, it would go up considerably at the end. 
 
If it was running rich, it would go down at the end of that little lip. 

And then depending on how efficient the coil is at using the energy, you may or may not see some of these oscillations at the end. 

If you see some extra little up and down oscillations there at the end, that just indicates it didn't use all the energy to create the spark and it just had a little bit leftover so it needs to dissipate. 

So easy way to test a coil and see if is the cylinder running rich the cylinder running lean? 

Is the coil even firing at all? 

You can tell all that just by looking at that voltage.