Fuel System Questions?? parts and what they do?

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

>      there is on the back of  the FD a unit that looks like a mushroom with 
>      fuel lines coming and going, could not find it in the Bentley book, 
>      What does this guy do for a living?

It sounds like a noise suppressor.  Does a 19mm open-ended wrench fit it?

>      The Pressure regulator, on the block (2lines) how does it work? are 
>      there common failure modes?

Yeah.  They go wrong.

That's not as flippant a remark as it seems.  The device's purpose is to 
provide control pressure to the FI system - low at cold startup, stable at 
warm, and in some cases to provide enrichment under load and compensate for 
altitude.  Sometimes (rarely) the electrical heating elements fail.  Sometimes 
the control pressure is wrong when cold, sometimes when warm - sometimes up, 
sometimes down ...
 
>      Are there rebuild kit for the FD?   

Yes.  Forget it.  _VERY_ non-trivial.  
 
>      What holds fuel pressure at the injectors?

Yurdge.  Read Probst's excellent book (published by Bentley).

>      there has to be check valves in the fd itself...

Varies by FD - check mechanisms, constrictions, etc.

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