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Summary: Audi fuel pump.
Just a summary, I fixed the problem it was a broken
From: firstname.lastname@example.org (Glen D. Powell)
Subject: Re: Audi fuel pump II?
Audi (Bosch) fool pumps can fail in an over-pressure failure mode.
This can cause irreprable damage to the fool distributor and/or to
the warm-up regulator. I seen it happen ($$$) :(
Nasty noises fromt he fool pump are a good indicator of impending failure.
It sounds like you now know this.....
My 85 Audi Coupe GT (same engine as the 5000) doesn't start
My girl friend has been using it for a while. The symptoms
she reported are: Driving along and suddenly black smoke
is coming from the exhaust and the drivability is bad, also
said there was a clicking sound coming from the rear of the
car(fuel pump?). Haven't had much time to look at it but
it doesn't start. The engine cranks over fine, touched the
fuel pump and that felt like it was turning(no noise).
I haven't had time to check the ignition system but this
seems like a fuel problem to me. How can I verify my
diagnosis? Should I remove an injector an try and start the
engine to see if any fuel comes out? Is there a better way?
>From the black smoke I assume it was running way too rich.
Some time ago I remember someones article saying that if
your fuel pump is making funny noises change it right away
as it could fail and distroy other components of the fuel
system. Which are these other 'components' of the fuel
system. What do they look like and where are they located?
How should I check them to be sure they are broken?
The saga continues:
I have done all the checks, relay, ground wires, changed spark plugs.
I checked the fuel flow, I have fuel flow all the way to the fuel
distributor. I removed a injector connection from the distributor and
tried to start it, but no fuel came out of the distributor.
I then removed the distributor and found the plunger to be very stiff.
The air flow plate would have a hard time pushing the plunger.
When I completely removed the fuel distributor and all the fuel ran
out of it, the plunger was freed. It seemed the plunger was
'pressure locked'. I reconnected every thing and low and behold the
engine started. It was running fine, but the fuel pump was making
much more noise than it used too. The engine then died, ran for about
a minute. I didn't disconnect the fuel distributor again but I assume
the plunger had become 'pressure locked' again. Some how the fuel
after the plunger would get locked in and the air flow sensor would
be unable to push the plunger.
Then I checked the fuel pump once more. It obviously worked, but how?
Could it be that it had failed in a very high pressure mode???
Is this mechanically/electrically possible???
The specs for the pump say it should take 8.5 amp at 11.5v.
As my digi-meter only goes to 10amp I didn't want to connect it to
measure the amps. I measured the pump resistance instead.
It was about .9 ohms, that gives 12.8 amps at 11.5v .
I wonder how accurate this is? Does the internal resistance of a DC
motor change when it is working??
I know that it changes for a AC motors.
>From all of this I diagnose that the fuel pump failed,
over pressurising the fuel distributor.
Do people agree/disagree with this???
If this is the case, did the increased fuel pressure from the pump
break the fuel pressure regulator in the fuel distributor? The
distributor also contains pressure regulators for each injector.
I am not convinced that the fuel pressure regulators in the distributor
are broken as the engine 'seemed' to run 'ok' for a minute, before the
fuel build up in the distributor stopped the engine.
How likely is this?
From: Dave Mills <email@example.com>
Did the black smoke and poor performance happen all of a sudden?
If so, then I think that your fuel injection system/computer went
into "fail-safe" mode. Something similar happened when I lost a
ground to the "brains" in my Audi 4000. Check around to see if
anything is loose that shouldn't be.
Good Luck (and let me know what happens),
From: firstname.lastname@example.org (J Mcclellan)
Subject: Re: Audi fuel pump??
Black smoke => too much fuel => fuel pump is delivering
check for a stuck-open injector or a broken or loosened
fitting that leaks fuel into the manifold.
The clicking noise would be from the pump running continuously
to try to supply the extra demand.
Possible cause could be a stuck pressure regulator => high
pressure in the fuel log breaks something, also causes fuel
pump to sound funny.
Good luck, these things can be awfully frustrating.
From: email@example.com (Bob Rusk)
To: firstname.lastname@example.org (Stamos Stamos)
Subject: Audi fuel pump??
I don't know diddly about the particulars of the Audi fuel injection system,
but it is quite likely that, having had black smoke followed by no-start,
your plugs are fouled. It may well be that if you clean or replace the
plugs, the engine will at least start. And I've always found it easier
to diagnose an engine that starts. :^)
From: email@example.com (Paul Austgen)
Subject: Re: Audi fuel pump??
Sender: firstname.lastname@example.org (Usenet News)
Date: Thu, 23 Jul 1992 20:23:30 GMT
Organization: HP Colorado Springs Division
There is an output diagnostic sequence that you start with a
short circuit over the fuel pump relay. It will check the fuel
pump, cold start valve, etc. It would seem to me that the cold
start valve would be the easiest and safest point to check for
fuel delivery. I don't know how this sequence works for
non-turbo's. It varies with engine types and years.
From: Alden Jackson <email@example.com>
Stamos, I wish I could tell you exactly where to look. Alas, I am
not familiar with the 5000 series engines. Also, I didn't find the
problem myself. I worked for about 3 months trying to figure out what
was wrong. No luck. I finally took it to the place that I trust to
do the jobs that I can't/won't do. They put it on their Bosch
analysis "dohicky" and figured it out what was wrong almost
immediately. It took them a while to figure out WHERE the ground was
missing. From all that, I believe that there are several good places
for you to start looking:
1) Connection(s) to/from control unit (under the glove box in my car).
Check all these, and make sure that they are secure. Sometimes the
unit is grounded by a bolt also.
2) Check around the fuel distributor and the fuel flow meter. There
are connections for various sensors that assume the body/manifold is
grounded. (I was missing one here (underneath that rats nest of fuel
lines 8-). I had to remove the connection to the frequency valve to
get the car to run at all.)
Do you have a Bentley manual? It can be invaluable in helping you try
to track down the problem. If nothing else works, try to find someone
in your area to evaluate the fuel control system and let you know what
From: bernie@metapro.DIALix.oz.au (Bernd Felsche)
Subject: Re: Audi fuel pump II??
Organization: MetaPro Systems, Perth, Western Australia
Date: Sun, 26 Jul 92 08:56:19 GMT
firstname.lastname@example.org (Stamos Stamos) writes:
>From your description, it could well be the control pressure
regulation circuit. Tu turnedhis acts on the top of the plunger to
"fine-tune" the plunger stiffness against the metering plate
There is a small piston in the side of the fuel distributor
which does the actual regulation. Connected to it, is a line
to the control pressure regulator, mounted on the engine
block. This is also called a cold-start regulator, though it
does a lot more than that.
Disconnect the fuel line to the control pressure regulator
(careful, lots of fuel) and see if the plunger moves easily.
If it does, then you probably have a faulty control pressure
regulator -- or maybe just a clogged fuel return line.
If the plunger does not move freely, then the control piston
(or push valve) is stuck. You'll have to dismantle that
section of the distributor to see the cause, but be very
careful with the parts... This would be about the last thing
to go wrong. A stuck regulator can mean replacing the fuel
distributor. It's not very likely that it is broken because
you got it moving after venting pressure.
A little more likely, is that the control pressure regulator
on the side of the engine has failed in a strange way,
causing the control pressure to be too high.
>The specs for the pump say it should take 8.5 amp at 11.5v.
>As my digi-meter only goes to 10amp I didn't want to connect it to
>measure the amps. I measured the pump resistance instead.
>It was about .9 ohms, that gives 12.8 amps at 11.5v .
>I wonder how accurate this is? Does the internal resistance of a DC
>motor change when it is working??
Actually, the current draw depends on the pump load
(pressure and internal friction) so simply measuring the
winding resistance is not sufficient. If you don't want to
burn your multi-meter (most will take more than 20 amps even
though they only claim 10 amps), then put a small resistance
in the fuse position, and measure the voltage drop. (I trust
I don't have to tell you how to select a resistor.)
>From all of this I diagnose that the fuel pump failed,
>over pressurising the fuel distributor.
>Do people agree/disagree with this???
I do. The fuel pump, if it is really dead, failed as a result
of an over-pressure condition. The fuel pump has probably
shut itself down and will work when the problem is
>If this is the case, did the increased fuel pressure from the pump
>break the fuel pressure regulator in the fuel distributor? The
>distributor also contains pressure regulators for each injector.
>I am not convinced that the fuel pressure regulators in the distributor
>are broken as the engine 'seemed' to run 'ok' for a minute, before the
>fuel build up in the distributor stopped the engine.
If the engine always restarts after venting fuel pressure,
then it's the pressure regulation circuit. Probably -- a
faulty return line. Maybe something hit it and caused it to
be closed or partially restricted.
Get a large clean container and disconnect the fuel return
line(s?) and allow them to drain into the container (you'll
probably want to tie them down unless you're an octopus).
Try to start the engine again.
If the engine runs with return flow to the containers, then
fix the return line under the car (and send me 200 chocolate
Let us know how you go...
+-----+ Bernd Felsche _--_|\ #include <std/disclaimer.h>
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