Bosch K-jetronic question: warm-up regulator
Disgusted of Tunbridge Wells
in the Bosch K-jetronic fuel injection system such as that used on the
mid-1980s Audi 100? I am trying to do a remote diagnosis of a
no-start situation for someone who has the same car. Mine seems to
start equally well whether the warm-up regulator is connected up or
not.
Ero Rademer
Hi.
I've driven such a vehicle with the K-jetronic. The warm-up regulator
*lowers* the control (fuel-)pressure of the ....... er .... 'thing with
the
mass air plate and the fuel delivery rails to the injectors' when cold
(bi-metal spring inside) so the mixture is shifted slightly to the rich
side.
The regulator is heated by the block and additionally by electrical
power.
As an aside, the regulating membrane inside is pulled by the vacuum of
the engine. On full throttle, there is less vacuum to the membrane
and the mixture is richened to provide full boost.
Error conditions (from own observation):
- When the (permanent) electrical heating does not work (or is
unplugged),
you get an over-rich mixture after a few minutes of driving (car
sputters) due to the block not heating that fast. This condition
should
revert to normal when the block is fully warmed up.
- When the membrane or bi-metal spring do work erratically, your car
usually starts normal but drives a little sluggish. This is because
the cold start injection valve sprays additional fuel into the intake
on very cold mornings and full throttle. Fuel economy decreases.
- When the vacuum tube is not connected, the mixture is slightly too
rich.
Fuel economy might decreases. On mine there were two openings
suitable
for a vacuum tube, one of them was covered with a plastic cap, dunno
why.
Conclusion: A faulty warm-up regulator should not hinder to start the
(cold!) engine. So take a closer look to the ignition, distributor (hall
sensor!) and spark plugs (BTDT). Dripping injectors (cold start valve,
too)
can cause this engine to not start instantly after sitting overnight.
After long cranking, try unplugging the electrical connector to the cold
start valve. If I recall correctly, these engines did not 'prime' the
fuel pump when turning the key to 'ignition on' prior to cranking. Can
you hear the fuel pump buzzing while cranking?
HTH
So long!
Ero.
--
Ero Rademer ANTISPAM in effect.
Fraunhofer Institute Use this: e...@rademer.de
for Computer Graphics
http://home.germany.net/101-137709/rademer.html
Graham
On Thu, 26 Oct 2000 16:13:02 GMT, JPF
<frickjpremo...@theoffice.net> wrote:
<snipped excellent content>
>A warm car requires much less fuel, and you have an oxygen sensor to
>trim the mixture, so they usually run warm. The oxygen sensor works
>in conjunction with the frequency valve which also regulates control
>pressure. Cold, it is at 50%, the base setting. JPF
>
Just to add to the above as I think JPF is based in the States, the
Bosch K system as used in the UK did not have Lambda control til the
KE version.
Graham
wrote:
>
>The regulator is heated by the block and additionally by electrical
>power.
>As an aside, the regulating membrane inside is pulled by the vacuum of
>the engine. On full throttle, there is less vacuum to the membrane
>and the mixture is richened to provide full boost.
>
>Error conditions (from own observation):
> - When the (permanent) electrical heating does not work (or is
>unplugged),
> you get an over-rich mixture after a few minutes of driving (car
> sputters) due to the block not heating that fast. This condition
>should
> revert to normal when the block is fully warmed up.
Above correct
> - When the membrane or bi-metal spring do work erratically, your car
> usually starts normal but drives a little sluggish. This is because
> the cold start injection valve sprays additional fuel into the intake
> on very cold mornings and full throttle. Fuel economy decreases.
The cold start valve has nothing to do with the warmup regulator. On
the basic K system the cold start valve is controlled via a thermo
time switch. On *some* KE systems the cold start valve is controlled
by the ECU.
> - When the vacuum tube is not connected, the mixture is slightly too
>rich.
> Fuel economy might decreases. On mine there were two openings
>suitable
> for a vacuum tube, one of them was covered with a plastic cap, dunno
>why.
>Conclusion: A faulty warm-up regulator should not hinder to start the
>(cold!) engine.)
Probably 98% of failures of the warmup regulator are caused by either
dirt blocking the galleries or rust (from contaminated petrol) doing
the same. This blockage invariably results in high control pressure
both hot and cold. This constant high control pressure then provides
no cold running fuel enrichment. Starting will be akin to starting a
carb equipped car with no choke, very difficult, often impossible.
>So take a closer look to the ignition, distributor (hall
>sensor!) and spark plugs (BTDT). Dripping injectors (cold start valve,
>too)
>can cause this engine to not start instantly after sitting overnight.
Faulty injectors causing leakage usually create a hot start problem.
It is very rare for system pressure to be anything but zero after
overnight (8 hrs?)
Dave Baker
>From: disg...@tunbridge.wells (Disgusted of Tunbridge Wells)
>Date: 26/10/00 16:07 GMT Daylight Time
>Message-id: <39f8489...@news.ukgateway.net>
Other excellent answers have already been given - I'd just add that if you want
to get deeply into FI system troubleshooting you ought to get a copy of "How To
Tune and Modify Bosch Fuel Injection" by Ben Watson ISBN 0-87938-570-7.
Covers all the major systems with test procedures for fault finding.
God must love crazy people - he sure made enough of them. Engine technical
articles at http://members.aol.com/pumaracing/index.htm
Ero Rademer
Geoff wrote:
> <pedant mode>
> It's the other way around. Engines with the vacuum connection are set
> to run slightly lean at idle. At full throttle the *increase* in
> manifold pressure pushes the membrane down, dropping the control
> pressure thereby richening the mixture.
> </pedant mode> :-)
I know that's what most of the *books* say. I always wondered why my
"ECON"-gauge (which was actually a mechanical vacuum meter -- don't know
if this thing was ever brought to the US or UK models, it was standard
on two of my Audis) was at "full" when the engine was off.
Laying on the table unconnected to anything it shows "you are using
MUCHO fuel" and sucking on the connector it went to "low fuel usage"
like on
idle. A leak in the vacuum system was indicated in the needle not
returning to its zero position on idle (or coasting).
So "Full Throttle" meant "almost no vacuum" at the gauge.
And the gauge was connected to the vacuum system which went to the
distributor, the warm-up-regulator and the tin box which fires the
cold start injector when you push the throttle *fast* (not deep) and
engine cold.
This was with all my Audis (80 1979, 1.6 55PS, 100 1982 1.8 75PS,
100 2.0 115PS, 80Q 2.0 115PS) On all of them with vacuum brake booster,
you can feel a (very slight) improvement in brake assistance when the
engine idles or coasts compared to full throttle (try car in neutral,
apply throttle and brake simultaneously and keep brake pressure constant
for a while, then let the engine idle).
Taking a look at the pictures in my "books", the vacuum line is
connected
*after* the throttle plate. So the most vacuum you have when the engine
is coasting down a hill and the throttle is closed. This was the reason
I never bought them claiming the ignition timing is altered with
"increasing
vacuum" while applying throttle. Going by the book, detaching the vacuum
line from the iginition advance box should have made the engine ping
under
load. It didn't.
For me, reality takes preceedence over the books. :)
[But yes, IIRC, one book says something about "at 3/4 throttle the
vacuum is
lowest and increases a little going further to full throttle." Might be.
I was never able to observe this on the ECON-gauges. As you probably
see,
I'm tinkering with this problem for long now. Perhaps we can shine a
light
on it THIS year...]
So long!
Ero.
P.S.: And yes, I confess, I ran my car with the vac. tube disconnected
from the WUPreg: no change in drivability or starting (always fine).
I ran the car with the cold start valve disconnected: started always
fine.
I ran the car for years with this "fast throttle fuel injection thing
(FTFIT)" disconnected: always started fine, also in winter (and it did
not
failed emission tests.) But the car had 320000km on the clock when I did
that...
The car only ran bad with the electrical plug disconnected from the
WUPreg
and when I "shorted out" the "only when cold"-vacuum valve for the
FTFIT...
Disgusted of Tunbridge Wells
Thanks to all who have replied. The problem has apparently been
diagnosed as poor compression. Some work was done yesterday to
increase the compression artificially (sounds suspect) and the car now
starts and runs for a minute or so at idle but stalls at higher revs.
Sorry I can't be any clearer than this: the car is 1000 miles away
and information is coming back second-hand. Any further hints will
be much appreciated.
Disgusted of Tunbridge Wells
<ge...@chilling-out.demon.co.uk> wrote:
>On Sat, 28 Oct 2000 06:50:38 GMT, Disgusted of Tunbridge Wells wrote:
>
>>Thanks to all who have replied. The problem has apparently been
>>diagnosed as poor compression. Some work was done yesterday to
>>increase the compression artificially (sounds suspect) and the car now
>>starts and runs for a minute or so at idle but stalls at higher revs.
>>Sorry I can't be any clearer than this: the car is 1000 miles away
>>and information is coming back second-hand. Any further hints will
>>be much appreciated.
>
>Questions for your friend... :-)
>
>1) Does it run for *more* than "a minute or so" at idle if you let it?
>2) What state are the electrics in - is there a nice blue spark?
>Plugs OK? What about the coil?
>3) When it stalls does it just die or does it cough and splutter while
>it's doing it?
>
Well, after further analysis it was concluded that both the ignition
and fuel systems were OK and that the source of the problem lies in
weak piston rings. So it looks like an engine rebuild job.
Fortunately, this having happened in Eastern Europe, labour rates are
cheap and Audi expertise fairly widespread: they expect a potential
bill of no more than GBP 250 including parts.
Thanks again to all who replied.