MB fuel injection pressure controls

[quk@isham-research.demon.co.uk (Phil Payne)]

Esoteric, I know.
 
I bang on a fair bit about this, and I realise that - even for the committed - 
this is only of academic interest .. but I'm trying to understand the MB's 
weird fuel injection controls.

Unlike the WR, the MB has no system pressure control in the metering head.  The 
warm-up regulator, which Charles Probst suggests should be referred to as a 
'control pressure regulator', is indeed purely a warm-up regulator on the MB - 
there is no vacuum connection for open throttle enrichment.
 
Both of these functions - system pressure regulation and control pressure 
regulation - are supposedly carried out by a combined valve mounted on the back 
of the air filter box.  This has a vacuum connection - to mimic the WR's vacuum-
controlled 'warm-up regulator'?
 
Whatever - a series of test runs this evening with a vacuum pump ably operated 
by my daughter suggests that feeding vacuum into this combined valve has as 
much effect as approaching an ovloV from behind at considerable closing speed.

Nothing happens.

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club