Date:         Sat, 28 Apr 2001 16:02:33 -0400
Reply-To:     David Beierl <dbeierl@attglobal.net>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@attglobal.net>
Subject:      Re: Fuel Injection Adjustment
Comments: To: Mark Keller <kelphoto@islandnet.com>
In-Reply-To:  <3AEB2620.B5766800@islandnet.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 04:20 PM 4/28/2001, Mark Keller wrote:
>supply to the fuel pressure regulator, say 10" at idle as opposed to 12"
>at idle, then pull of vacuum motor on the fuel pressure regulator would
>not be able to overcome the spring pressure on the valve seat and thus a
>higher fuel pressure at idle would occur.  How much?, does it matter?, I

Slight misconception here -- the fuel regulator dynamically controls the
fuel pressure to be constant *relative to the manifold pressure* -- if the
manifold pressure rises (less vacuum), so does the (gauge) pressure in the
fuel rail -- but the pressure from inlet to outlet of the injectors remains
constant.  The regulator could be setting the wrong pressure, but whatever
its setpoint is, it will follow the variations in manifold pressure exactly.

To demonstrate this, mount a fuel-pressure gauge in an airtight box and
connect the box to manifold pressure -- result should be a constant reading
on the pressure gauge regardless of manifold pressure (subject of course to
transient fluctuations as conditions change).  Make sure the box is strong
enough to withstand the low pressure without collapsing.

david


David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"