Narrowing down my start issue (84 4kq) [with suggested procedure]

[Henry A Harper III]

While they both do modulate the CIS basic fuel pressures, the WUR is more
temperature-based (mounted to the block) with a
known-electrical-characteristic heating element to phase out its modulation
after engine warmup (AIUI, I don't have a CIS car). On the other hand, the
DPR in my CIS-E GTI 16v is actively controlled with an electrical current
from the CIS-E "brain" (analog though it is) throughout engine operation to
provide not only warmup regulation based on engine coolant temperature but
also the closed-loop stoichiometric mixture adjustments. So yes, and no?

> -----Original Message-----
> From: quattro-bounces at audifans.com
> [mailto:quattro-bounces at audifans.com]On Behalf Of John Cody Forbes
> Sent: Tuesday, August 17, 2010 10:34 AM
> To: Ben Swann
> Cc: Johnny B; <quattro at audifans.com>
> Subject: Re: Narrowing down my start issue (84 4kq) [with suggested
> procedure]
>
>
> Correct me if I'm wrong, but isn't the DPR essentially a WUR in a
> small plastic case and mounted to the metering head?
>
> -Cody (mobile)
>
> On Aug 17, 2010, at 12:21 PM, "Ben Swann" <benswann at verizon.net> wrote:
>
> > Cody,
> >
> > This is probably why they did away with the WUR and went CIS-E.
> Indeed, the WUR is the
> > main reason these fuel pressure tests were used.  CIS-e does
> not use it (WUR) and
> > basically there is less need to do fuel pressure tests.  BTDT
> thinking I'd trouble shoot
> > CIS-e the scame way as CIS, only to find out it became an
> irrelevant waste of time, and
> > all the connections were competely different from CIS.
> >
> > This reminds me of the story about the old man called out of
> forced retirement to fix a
> > critical system so folks could have their Electiricity back.
> He used to work on the
> > system that he helped design and implement.    The officials
> stood around watching as he
> > climbs down a manhole with a large screwdriver and comes up
> less than a minute later
> > after turning a control switch with the screwdriver.  He hands
> them the $500 bill and
> > they complain - Why so much? since all he did was to turn a
> screw to reset a breaker.
> > He replied, " Yeah, but I know which screw on which control
> panel and in which manhole
> > in which street."  "Come to think of it, don't you think I
> ought to charge you more -
> > how much is the outage costing you per minute?"
> >
> > Ben
> > -----Original Message-----
> > From: John Cody Forbes [mailto:cody at 5000tq.com]
> > Sent: Tuesday, August 17, 2010 10:14 AM
> > To: audi at humanspeakers.com
> > Cc: Ben Swann; quattro at audifans.com; Johnny B
> > Subject: Re: Narrowing down my start issue (84 4kq) [with
> suggested procedure]
> >
> > I have two five gallon buckets filled to the brim with bad warm
> up regs diagnosed with a
> > simple fuel pressure test that takes 5 minutes. Changing parts
> on hunches and well meant
> > educated guesses may work for those with parts cars or a fleet
> of similar cars, but in
> > the professional world my customers don't want to hear "yeah I
> changed the temp sensor,
> > see if that works". There is a test procedure for everything
> that can lead to fixing
> > problems by only changing the things that are actually broken
> 90% of the time. I
> > understand that not everybody has all of the equipment that a
> shop does, but in this
> > case a fuel pressure gauge set is very inexpensive (cant they
> be had at Harbor Freight
> > for like $40?) and would take a minute or two to install and
> KNOW what is going on with
> > the fuel pump, injectors, DPR, and others. CIS is not like a
> carb or EFI system where
> > the system pressure is important, but can be 10% off before
> it's noticeable to the
> > driver. The system pressure on CIS is not even very important,
> but the control pressure
> > that controls the movement of the metering plate is *critical*.
> >
> > Now with that all said, is it possible this problem is ignition
> related? OP mentioned
> > that the PO changed many things in the fuel system and had it
> looked at many times.
> > Could it possibly be that he was barking up the wrong tree?
> IIRC the car in question has
> > a basic ignition system (vacuum advance distributor, no ECU),
> right? It's sort of
> > unlikely, but maybe the advance is sticking all the way
> retarded for a time?
> >
> > Also, a smoke test would be pretty useful just to be certain of
> the vacuum system. I've
> > made a "smoke machine" before out of a quart paint can with the
> lid soldered shut, some
> > WD-40 or ATF as smoke fluid, two pipes soldered to the sides to
> let air in and smoke
> > out, a propane torch to make the smoke, and an electric tire
> pump to do the air moving.
> > Sounds silly, but I discovered and fixed a few small leaks on a
> car that way.
> >
> > -Cody (mobile)
> >
> > On Aug 16, 2010, at 2:35 AM, Huw Powell <audi at humanspeakers.com> wrote:
> >
> >>
> >>> Now that you have gotten to the point of things that Cody and Huw,
> >>> and others are pointing out, they may want to suggest clever ways to
> >>> do these tests.  Although I have done most of these in my ownership
> >>> of CIS cars, in most cases I never needed to go to the point of fuel
> >>> pressure tests  since I usually got things sorted by then.
> >>
> >> I have never - NEVER - seen any need for fuel pressure tests.
> >>
> >> Vacuum leaks and the resulting maladjusted static fuel mixtures,
> >> endlessly.  On almost every CIS engine I have encountered.
> >>
> >> --
> >> Huw Powell
> >
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