Primary vs secondary ignition waveforms

I am new to the world of having a scope. Just recently got a u scope from aes wave and I have been looking at waveforms on vehicles that i have access to. I have been using the secondary pick up on some early 2000's fords and been getting good waveforms on the cop coils and plug wires on different motors. However I tried to use it on a 2015 ford fiesta and could not get a good waveform on it. So this had me wondering if it would be better to look at the primary waveform. How do the primary and secondary waves relate and can you get all of the same information from both? Also what is the preferred one to go after?

Congratulations on the uScope! You're gonna love it, they're fantastic.

For our reference, what kind of ignition design does that Fiesta use? COP? Waste spark? I ask because Ford has introduced a few new coil designs, and none of them allow for good secondary waveforms with a typical COP paddle. Been there, tried that.

Worse, Ford has jumped on the three wire COP bandwagon, which means no primary voltage waveforms. :lol: The only comfort is that some of the waste spark and two wire coils offer spark duration data PIDs in scan data.

Primary and secondary relate very strongly to one another, but it's usually preferable to look at the secondary, since it will tell you more about what's going on inside the cylinder. Not that there's anything wrong with using primary voltage, it just won't be as informative about cylinder conditions overall. It's all about what you have to work with.

As an example, here's a couple waveforms I got off an '03 F-150 with a weak coil. The first is the coil primary voltage, and the second is secondary.





Both show the same coil failure. No turbulence in the burn line, no coil oscillations, very short burn time. Either one could have been used without issue. Really, I think the primary waveform told the story better - you can see that there's current flowing through the primary, but there's nothing happening in the secondary.

51 minute mark.

The fiesta i was playing around with was a 1.0 ecoboost 3 cylinder and had 3 wire coil on plugs (best I remember). Thanks for the help.