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@BrickMan
The saga of the w203 mercedes continues.
Finally worked out what is killing it, known as 'saddle tank syndrome' or half tank = empty syndrome. A weakness in the design which relies on a particular speed of fuel movement exiting the low pressure return line to the left hand tank which if too low means all the returned fuel stays in the left hand tank and not splashing back over to the right hand tank. Which means when you have anything less than an indicated 30 litres of fuel (between the tanks) it starts sucking air, as the right hand tank is basically bone dry.
Its either.... 1 or more injectors leaking off too much (providing a short cut for the return fuel), o ring seals (in 1 of 4 places within the fuel rail) leaking (providing a short cut), high pressure pump isn't quite strong enough but not so weak as to trigger an EML or even show up on my live feed, low pressure pump not strong enough (no data for this, you just have to watch it coming out of a tube back into the tank), return line clogged, feed line (any of them) sucking air through a perished o- ring causing air to be in a fuel line when there shouldnt' be (which gives same symptoms as above), or a combination of the above.
Had a mate who is an ex mercedes main tech (now works an independent) who can't track it down, other than we reckon the injectors are fine, he would guess HPP/LPP (get it rebuilt or just buy a new one).
Fuck me, why did I bother, should have just stuck it with the volvo engine rebuild. Newer cars are too complicated!
ALso changing the thermostat because looking at service history it has failed every 3 years like clockwork (mercedes/behr, mahle, circoli and most recent has no name all failed the same). Car never really warms up, sits at 60-70C when it should be about 80-85c. Easy to change but the new 'Behr' part that just arrived in the post is a fake, yeay.