Fw: CIS Diagnostic, help

[rob hod]

    Anyone spot my own bad? , the gauge tap should be on the warm up reg
side!

rob
----- Original Message -----
From: rob hod <rob3 at hod3.fsnet.co.uk>
To: <quattro at audifans.com>
Sent: Tuesday, May 07, 2002 1:55 PM
Subject: Re: CIS Diagnostic, help


>
>     Steve,
>
>     Looks like your testing at the right point, probably a silly question
> but do you have the meter connected with the isolator tap on the right
> side?, - tap towards fuel dist side?, If so then tap open = control
pressure
> reading, tap closed (engine off , fpr jumpered ) = fuel system pressure.
>
>     BTW the bit you are requoting says "They could have used a spring, but
> using fuel pressure
> > > instead of a spring helps to compensate for minor fuel pressure
> differences,
> > > and saves needing another calibrated spring."
>
>    Don't like to nitpick but this is wrong, - Control pressure, not system
> pressure, is used to oppose the air flaps' movement, and the reason is
that
> control pressure, being regulated by the warm-up reg and any altitude
> correction, determines the basic mixture (further modified by oxs/dpr in
> emission control cars).
>
>     HTH.
>
> rob
> >
> > Message: 7
> > Date: Mon, 06 May 2002 20:40:49 -0600
> > From: Steve Sherman <spsherm at attglobal.net>
> > Reply-To: spsherm at attglobal.net
> > To: Bernard Littau <bernardl at acumenassociates.com>
> > Cc: quattro <quattro at audifans.com>,
> > Ben Swann <bswann at worldnet.att.net>
> > Subject: Re: CIS Diagnostic, help
> >
> > Bernard
> >
> > Thanks,  I have been taking the presuure readings per Probst and the
meter
> > instructions; the meter goes between the fuel dist and the warm up
> regulator
> > (aka control pressure reg).
> >
> > I reran the test again tonite, both pre and post a new fuel filter.
Same
> > numbers, both ways.  There was a short (1-2sec) spike up to 70# but that
> was it,
> > then the numbers held at 40-50#.
> >
> > I had hoped to put the meter on the end of the fuel filter, to see if
the
> pump
> > alone was capable of reaching higher pressures, but unfortunately the
> meter kit
> > I got (J C Whitney special) does not have that fitting.  I am going to
try
> and
> > find or fabricate this fitting.  I think it could be the decisive test
as
> to
> > whether or not the pump can cut it, or whether as Ben Swann suggested in
> another
> > post (and you mention), the problem lies in the pressure reg.  It seem
> that the
> > problem is most likely one of these two...
> >
> > AFWIW, when i drained the gas out of the old filter, it was mstly clean,
> but
> > towards the end a cloud of fine black "stuff" came out of the dirty
side.
> > Possibly that fuel tank liner thing clogging the pump intake.
> >
> > Did not get to do the flow test, as it was getting dark, will hopefully
> get
> > there tomorrow.
> >
> > Agreed on the plugs, obviously a short term thing, probably as I was
> limping
> > home before if finally died.  Not a biggie as under the thin layer of
> soot, the
> > plugs looked fine.  But as I read Probst (and I've been doing that alot
> lately
> > ;-) lower fuel pressure does enrich the mixture, odd as it seems.
> >
> > Several have said that the additional pressure on the air plate is
normal,
> so I
> > guess I got excited over nothing on this.
> >
> > Hopefully another day of testing will turn up the smoking gun; if not,
> pretty
> > soon I'll have to cry uncle and call in the experts.
> >
> >
> > Steve
> >
> >
> >
> > Bernard Littau wrote:
> >
> > > Hi Steve,
> > >
> > > I'm no expert, but I have read the Probst book on the Bosch CIS.  I
have
> > > also had to deal with a low fuel pressure problem on my car -- with
> major
> > > help from local listers, including the loan of the Probst book :-)
> > >
> > > Fuel pressure should be much higher than 40 or 50 pounds; closer to
90.
> > > Where are you measuring the pressure?
> > >
> > > This is correct behavior.  The fuel pressure pushes on the plunger,
> making
> > > it harder to raise.  They could have used a spring, but using fuel
> pressure
> > > instead of a spring helps to compensate for minor fuel pressure
> differences,
> > > and saves needing another calibrated spring.
> > >
> > > Plugs take some time to acquire a rich or lean condition.  It's likely
> you
> > > were running rich before your no-start situation.  A few cranks of the
> car
> > > won't change the plug's look.
> > >
> > > As above, the pressure on the plate is normal.
> > >
> > > I think you need to not link the fuel pressure to the plug condition.
> The
> > > fuel pressure is now, the plug condition is historical.
> > >
> > > Low fuel pressure is not going to make the car run rich, in fact, it
> will
> > > tend to make the car run lean.  This lean tendency can be compensated
> for by
> > > the ECU using the O2 sensor, so a car will typically run correctly
even
> with
> > > somewhat low fuel pressure under moderate throttle conditions.  At
high
> > > throttle the car will stumble.
> > >
> > > Rich looking plugs are most likely to suggest a leak in the air intake
> > > system -- the typical Michelin Man Hose leak is an example.  It seems
to
> me
> > > that it would be difficult to check for small leaks in the vacuum or
> intake
> > > system with the car not running :-)  You may want to address this
again
> > > after the car is running.
> > >
>
>