Engine cutting out on the track

[Finnegan]

Originally Posted by JayL

I'm bringing this one back from the dead because it happened again. Spent last Wednesday at COTA and while on my first hot lap the car died again. I ended up doing a few additional laps because there wasn't really anyone around me at the time and it always happened happened on right turns. Specifically turn 13, followed by 16, 17 and 18 if you are familiar with COTA.

The good news is I was finally able to get the car to do the same thing on the street while entering an on ramp so I hope to replicate this again tomorrow morning while recording some video. Maybe it will show something I'm missing which will help to diagnose this. I'm hesitant to throw parts at this or take it to a shop because of not knowing even where to start. Any ideas?

Not this time. Hmm. Do you have a way to record/log the BMW extended ODBII data? That might help with the diag.

[dre99gsx]

I mentioned this in another thread: Your pump/filter/regulator may simply be on their way out (if it hasn't just dislodged again). I had this happen to me at the track, but had data to back up. My fuel pressure would drop to ~0psi at full boost, a few times, but drove fine on the way home. I ended up replacing the entire fuel pump/filter/fpr assemblies, problem gone. Although I could have dug deeper to find which one was at fault, being 90k miles on my setup, these things should be replaced anyway.

[The HACK]

Car lost spark. Something is shorting out the electric system. If it was a fuel problem the car would sputter instead of the engine completely cutting out, since even without fuel the engine will continue to act as an air pump to suck the air in and the spark will attempt to ignite it. You will get a "ppptht-puuuuut" and the car would jerk while in gear, and the RPM decline wouldn't be smooth.

Based on the video, it looks like the engine is turning due to momentum, but zero spark in all cylinders. The engine turns alternator should provide spark, so I suspect a loose harness? The sudden change in G force cause a momentary disconnect? Does it only do it while turning in one direction only?

[JayL]

That's the best diagnosis I've heard so far. If the car wasn't in gear it would have immediately died. It does this more frequently on right hand turns but it's done the same thing on a few hard left turns as well. I typically drive like an old man on the street so this previously only happened on the track.

This upcoming weekend I'm going to do another once over and if I can't find anything it will likely be off to a shop for a little professional help.

[Manxman1950]

I had the same thing happen on another car (Caterham 7). Eventually tracked the problem down to a section of the wiring harness to the alternator being routed too close to the exhaust headers. The copper had gone brittle and broken - just required a new section to be spliced in and some improved heat shielding and all was well.