Audi 4000 S Quattro fuel system problem write-up.

Ben Swann bswann at
Fri Dec 6 10:33:43 EST 2002


I was confused too, until I looked at the CIS-E diagram.  I stand corrected
when I told Tyson it was a Differential Pressure Regulator, as even the
Bently shows it as a Diaphragm Pressure Regulator, and it is different than
the Differential Pressure Regulator.  Blockage I assume woule not allow
fuel return to the tank and therefore too high fuel pressure, either system
or control, though CIS-E does not really work with the principle of Control
Pressure as CIS does.  I guess I'll have to review my Probst again (and

I've never seen one of these go bad, but I suppose they can, especially
with bad gas or gas that has congealed from setting.

Nice writeup Tyson - you have definately educated yourself in a timely
fashion.  Congratulations!


From: "Bernard Littau" <bernardl at>
To: "Tigran Varosyan" <tigran at>, <quattro at>
Subject: RE: Audi 4000 S Quattro fuel system problem write-up.
Date: Wed, 4 Dec 2002 14:58:01 -0800

> Car: 1985 Audi 4000S Quattro CIS-E Fuel Injection 5 Cyl.
> Problem:
> Fuel delivery outflows the fuel return rate. The plunger was becoming
> pressure-locked and stopped fuel delivery.

Very nice write up, Tyson!

That being said, I am having trouble with the concepts of (A) the fuel
return rate being exceeded, and (B) the plunger becoming pressure locked
(C) high pressure causing fuel flow through the metering head to cease.

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