I love the way Scoping opens up areas for greater understanding & this is a good example of how it can lead you to the answers. Fortunately I had a Clio in today with the same kind of coil failure & it gave me a great opportunity to follow up on Saturdays research. Coupled with a study of a wiring diagram it all became a little clearer.

Here is the wiring diag..........




These coils are wired in "series" so that coils 1 & 4 are fired simultaneously & then coils 2 & 3 are also fired as a pair. This circuit arrangement also means that if there is a "break" in the circuit i.e. it goes open circuit, then the pair of coils will become inactive (rather like Christmas tree lights do ) I knew that these coils acted as a pair, but I had no idea how basic the circuit was. I carried out a few tests to confirm the actual layout of the circuit in real terms. On each coil, the upper terminal is the “feed in” & the lower terminal is the one that is switched. Here is a photo that hopefully makes it more clear......



On the Clio I tested today, I noticed the exact same effect that I saw on Saturday & now having studied the wiring diagram it makes sense. Coils 3 & 4 are not directly switched to ground, but instead the circuit continues through the other coils 1 & 2 respectively. This explains why the grounding on coil 2 is full & coil 3 is only partial.


The problem with this explanation is, that it means that my previous scope examples must be wrong. . In my first post, the "good" example after the fix, should display a fully grounded primary capture on cylinders 1 & 2. The thing is, I am very methodical about how I scope & save my files & I still have a niggling doubt that I have missed something. Only Time will tell, as I test a few more as they come in.

The Clio today looked like this…....


Cylinder 1 = Blue
Cylinder 4 = Red




Cylinder 2 = Blue
Cylinder 3 = Red



I hope I haven't confused anyone too much

Cheers for now