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

Tue Aug 17 10:34:34 PDT 2010

Yeah my phrasing could have been better, but in the end both are devices for modifying the control pressure and therefore the fuel mixture. They get there different ways and they are controlled differently, but in bottom line function they both do the same thing.

-Cody (mobile)

On Aug 17, 2010, at 1:01 PM, "Henry A Harper III" <hah at alumni.rice.edu> wrote:

> 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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> 