Stiff Plunger in Fuel Distributor

[rob hod]

    I think I understand what you are saying, but I don't think system
pressure comes into it *directly* .  Its probably best to regard the
resistance to upwards movement as being related to control pressure. Lower
control pressure = less resistance to upwards movement = higher airplate
posistion for given airflow = higher plunger in dist = more fuel = richer
mixture.

    Now as far as I know control pressure is controlled by warm up reg and
DPR only and remember that control pressure is derived by a calibrated
orifice from system pressure. There is thus a fixed supply of fuel and
pressure to the control system. This is how the warm up reg works - when
cold it bleeds off fuel in the control pressure system at a higher rate,
leading to lower control pressure. Having never had a car with a DPR (UK
dweller) I can;t vouch for it but I guess the DPR does a similar thing to
influence control pressure and hence mixture.

    Now concerning the downward movement of the air plate, I think there
should not be any significant amount. If released the plate should move
smartly back to rest with no hesitation, regardless of system or control
pressure.

    HTH

rob
> Message: 6
> To: quattro at audifans.com
> Subject: Stiff Plunger in Fuel Distributor
> Reply-To: awdaudi at excite.com
> From: "Jesse A Clendenning" <awdaudi at excite.com>
> Cc:
> Date: Tue, 26 Nov 2002 17:58:27 -0500 (EST)
>
>
>
> --
> [ Picked text/plain from multipart/alternative ]
>
> As I am still at work and do not have this problem - as of yet, I was
think=
> ing... I've read a couple of posts about stiff control plungers in the
fuel=
>  distributor and have experienced it once myself on an old 5000s. Most
peop=
> le assume that it is a result of the fuel pump running in an
"overpressuriz=
> ation mode." After thinking about this I believe that maybe this could be
j=
> ust the opposite. The difference between the pressure on top of the
distrib=
> utor and on the bottom of the distributor are what causes the pressure on
t=
> he plunger, correct? If there was excessive pressure on the bottom of the
f=
> uel distributor, wouldn't the plunger be easier to lift? Now if the
pressur=
> e were low from a failing fuel pump - then pressure would be as high as
pos=
> sible on the top side of the fuel distributor, and greatly reduced on
botto=
> m side - making a stiff plunger.  In the Bentley it describes cold control
=
> pressure (on top of fuel distributor) as being less than warm, making the
p=
> lunger move easier.  Does this seem to coincide with your theories? or am
I=
>  flawed in my views? I want to understand this better. Thanks, Jesse
Clende=
> nning
>
> _______________________________________________
> Join Excite! - http://www.excite.com
> The most personalized portal on the Web!
>
>