308 No spark at plugs for cylinders 4 and 8

John, Thanks you for taking a look. I really don’t know what the problem is but based on all the comments it seemed it was a good idea to once and for all eliminate the TDC sensors, flywheel pins, DigiPlex’s, and coils as the culprit. And if I am understanding you correctly, based on the scope readings, these ignition areas are OK.

Mike, your understanding is correct. I’ve tested everything multiple times and have verified that:

*Cylinders 1 and 4 DO NOT spark when the Green wires are connected at the rear coil (that is the stock wiring set up)
*Cylinders 2 and 3 DO NOT spark when the Yellow/Black wires are connected at the rear coil .

In neither scenario are all 4 cylinders firing, but I do know that the current is able to, in fact, reach each spark plug effectively. I’ve reposted a portion of that chart I made in post #25 to see what's happening.

And yes, with a spark plug directly on the coil output I was getting even and sequential sparks, which I believe is verified too by the scope readings, right?

Thank you all for thinking about this.
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That’s a great catch. I can’t confirm exactly what I was idling at, so I will test again and match the 1000 rpm’s and see the reading.
I did just look at the video of bank 5-8 reading too, and that blip seems to lean on the other side of the gap between firings.
In theory though, if my readings still look like this at 1k rpm, would it be a faulty sensor, or missing pin? But wouldn’t the 5-8 bank be affected too if it were a missing pin?
I’ll report back with revised test results and may even put my old (known working) sensor back in the 1-4 port in the sandwich plate.
Thanks as always.

 

Ok I'm back already and was able to snap a photo of the scope at 1000 RPMs. It is indeed about double the time between firings compared to your results for both banks (Sorry about the focus on bank 5-8 image). I guess the only item to maybe consider is how accurate these car's tach readings are, or is the margin of error not enough to matter. ..

 

Ok good plan. Thank you. I will test TDC sensors signal at 1K RPM also.

 

Well, mine look nothing like that at all. Here's the videos from bank 1-4 at 5ms and 10ms. (Bank 5-8 look similar. I will post those too later this evening...that's all the garage time I have today...) Thanks for taking a look. Any ideas on the cause?

5ms:


10ms:

 

Yes I love that that’s actually “good” news. The thing I am dreading though is a flywheel pin problem because that’s a lot of work. Can you tell if it looks like it might be the case also? I didn’t touch the digiplex’s in the trunk area at all when I refurbished the engine and bay. I can double check the grounds though. Is there anywhere else to look for ground issues? Thanks guys.

 

Thanks Steve, I checked both coil's ground, the 3 ground pins at the diagnostic port, the digi ground, (the point you indicated in the picture). All appear to be solidly ground, 0 to maybe 1 ohm resistance measured back to the negative battery cable. I'm assuming the next step in this process of elimination is to put my old TCC sensors back in, since they were working, and see what the results are. Would you agree and/or have any other suggestions for now?.

 

Correction- TDC sensors…. Not TCC..,,

 

John, Yes, the are Magneti Marelli. I found them on Amazon (link below). I cross checked that were the same ones - SEN8D, part number 119052 - offered at Maranello Parts and other Ferrari parts sites.
I wanted to confirm too that I was taking my scope readings by using the pos and ground pins for each bank in the diagnostic port.
I agree it does not make sense,...yet.... Can you recommend another test prior to me replacing these new sensors with the original ones?

https://www.amazon.com/gp/product/B00D76G09Y/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

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Well, I found the problem. I decided before swapping the sensors that since it's fairly easy to remove the RPM sensor because of its location, and I have a borescope camera, that I'd take a look once and for all and see if the flywheel pins are in there. As you can see from the photos, one is completely missing and one is bent. I didn't handle the flywheel very much at all when it was apart, but obviously something happened and I really should have checked it carefully before reassembly. That's a mistake I'll never make again.
It's a lot of work ahead but at least I know now what the issue is.
Thanks everyone for all your input and especially to Steve and John who stayed with me on this.
Will report back when all is back together again.

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Hello guys, been a while and here is the update:

As I said weeks ago I ultimately discovered by looking through the RPM sensor port that one of the TDC pins was missing from the flywheel, and the other one was bent.

So I took it all apart and found that there was a missing nut on one of the studs that holds the sandwich plate on to the engine body. (the nuts that are behind the flywheel). I also found a washer at the bottom of the housing that was all banged up. And there were also some nicks in the sides of the sandwich plate.

The assumption based on this is that the nut came off while driving and thrashed around behind the flywheel and knocked off one of the pins and bent the other.

Long story short, I put new TDC pins in the flywheel (also put in new location pins on the other side of the flywheel), and also had the flywheel recut since it was out…

Put it all back together and I was getting sparks at all cylinders and the engine started right up. Scope readings now look good.

Now on to fine tuning the fuel mixture and idle….

Thank you all again for your assistance in the diagnosis.