HPFP failure Bosch CP 4.2
https://photos.app.goo.gl/ScMUYcFu8gdsvXBp7
Pat,
photos in above link. Sorry about delay, only just checked forum; now on email notification.
In addition you can see this is an issue in Europe, here is an academic paper which clearly states there is a design weakness in this pump.
http://www.pan-ol.lublin.pl/wydawnictwa/TMot15_1/Osipowicz.pdf
As best as I can tell the problem is the cam roller failure, it stops rolling, you can see on my picture what happens next. Once it stops rolling the cam follower can turn (probably due to the pump action compressing a helical spring), I think once it has turned 45 degrees there is no force to straighten it up again even if it rolled again. But once it is sliding the generation of metal shards is deadly as the photos show.
What stopped it rolling seems to be the huge question, cavitation, surface fatigue causing pitting and jamming look possible on mine. All design weaknesses of course. On mine the other roller had flats (but not as bad as the 45 degree roller) so that had started to fail possibly due to contamination from the 45 degree one.
Tried to get Audi UK involved, no help whatsoever, complete denial, unbelievable response from so called premium manufacurer. Even had an extended warranty ($1700) that expired two thousand miles earlier, no goodwill.
I had car fixed at local Audi dealer, cost circa $4000. they repaced the HPFP and regulator valves and leak off pipes. Lasted 400 miles before engine light came on and into limp mode, now waiting dealer response.
I think the real fix needs pipes, fuel rails and injectors which at dealer prices would write the car off!
Pity we do not have class actions in the UK. As a retired vehicle engineer I would love to be a witness.
I have more if of interest on cam lubrication and other academic papers.
Let me know if you want more.