After a few years tollerating the check engine light I got tired of it and fix it. After a dozen of hp tuner scans with the laptop it came clear that the problem occured ocasionally and not permanent. At one scan I saw the low side fuel pressure drop fast. The high pressure stayed more constant. At all the other scans it didn't occured.
So I figured out that the high pressure fuel pump was dropping pressure at the low pressure side.
I replaced the high pressure fuel pump today and scaned it. No codes. I hope it is fixed now. It also was giving rich at the short and longtherm fueltrims. As before the replacement it was giving lean values all the time.
I keep you posted on the progress.
When you have one, you have to work with what you have not what you wish you had. 😬
Ring thickness on these beast is 1.2 mm, 1.5 mm, 2.0 mm.
Second ring is a taper faced unit. Top a PVD coated unit. Don't know the alloy.
Oil can not be to clean.
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