[Vwdiesel] Re: max fuel adjustment

William A. Thompson twogreek at hotmail.com
Wed Mar 31 18:28:21 EST 2004

Hmmmm ...

>"Will Taygan" and "H.Hagar"  wrote in a Thread

First ... at the bottom was ...
>I'm going pick up a copy of the bosch ve yellow book to see if I can internalize this.
>Ummmm   good idea.

I just received the new edition of the Bosch Book on our injection pumps from Bentley the other day. The old one was out of print when I ordered it months ago ... and they just put out a new version. Will ... come look at it if you want to ... it is pretty good in explaining the theory .. but lacks on specifications ... can't take measurement specs from the book ... as in it doesn't have 'em ... to determine if anything is out of tolerance. No measurements, volumes or pressures given except in a general sense. I think they might call that "proprietary information"? .. ... ... or "effective stealorship market positioning?" ... or the .. "bend over" position ???!!!
It does seem to cover the theory of all pumps in the VW line. I only have the NAs so I can't begin to evaluate it's treatment of the turbo/newer pumps. I am still ingesting and reflecting on the theory ... really haven't had enough re-reading and re-reflection time to best conceptualize it as yet ... but I plod on.
Does anybody know if the old Bosch VE book gave specs to evaluate the condition of the pump? How about internal adjustments/replacements for springs and such? They indicate that the internal parts are not interchangeable ... is such the case in the real world as to cannibalism? Any insight as to what a good authorized rebuilder can actually do?

>Is this right?
>Top of pump (screws connected to accelerator) controls the amount of
>fuel injected, thereby controlling idle and max rpm.
>Ummmm     not really.

I agree Hagar ... to the extent that I see the statement as correct as far as it goes ... but possibly misleading without context. All these adjustments affect the others and ... depending on how you look at it .. and the point in the process of adjustment that is being discussed .. the statement itself can't be judged without the context that is understood by the time this statement can be made and be valid.
By the time one gets to the point of final adjustment ... while making the top screw adjustments one could look at it this way in a sense ... and be effecting a fine tuning of low and max rpm as the final adjustments in the process.

>Side of pump controls max fuel given at a particular degree (of the top of pump accelerator control), in
>essence giving more fuel for the idle, more fuel for the mid range and more fuel for max at a given rpm,
>(raising the scale).
>Ummmm   not really.

Again I agree/disagree with the statement depending on the context. All the adjustments affect one another and all ... within the scope of their function/influence ... control the volume of fuel delivery for each gulp of fuel within the scope of their influence.
So far my take on it is that ...
To make the concept of the statements be more descriptive of what is going on ... isn't it more like ... load creates demand which the pump responds to by supplying more fuel. The full load screw on the side is adjusted for how much fuel is being dumped in according to load demand thru the rpm range ... while the top screws are then used to limit the rpm range by limiting fuel volume at their "end of the scale" point of influence.

It was kinda funny how my head got a little dizzy as I had to make the effort to change perspective while reading with tri-focals ... from carburetors and how they mostly use vacume to respond to load then use centrifugal force to respond to rpm ... and injection pumps using centrifugal force balanced against springs to respond to load then use pressure within the pump to respond to rpm. Likewise all of these adjustments end up being influenced by all the others ... and all are responding ultimately to load.
But it seems that ... at it's most basic description ... the full load screw on the side adjusts the volume of fuel delivered thru the rpm range and the two top screws then adjust the limits of the rpm range.

>PS:   My version on the way.

Yes ... Reality check appreciated ... please Hagar ... you other wizards too ... 

Sedro Woolley, Washington.

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