[Fwd: Re: Audi 100 Won't Start]

[Marc Boucher]

I too am thinking about the possibility of a vacuum leak in fact today I was 
trying to check the hose that runs from the ISV to the rubber air bonnet.  
I've checked all the visible hoses but its really difficult to check since 
car won't run for that long.  Any tips finding a vacuum leak?  It would (in 
my view) have to be a very large leak to prevent the car running.  I've 
disconnected small hoses  before without it shutting off the car.


>From: John Sherrow <sherrow at westol.com>
>To: quattro list <quattro at audifans.com>
>Subject: [Fwd: Re: Audi 100 Won't Start]
>Date: Mon, 26 Jan 2004 19:52:29 -0500
>
> >From the sound of your problem I would have suspect vacuum leak. If
>keeping the rpm's up keeps it running that's where I would start. Not
>very exciting to diagnose but it sounds familiar.
>
>I once had a similar problem when I knocked the plastic plug out of the
>air boot. After an hour of thinking about exotic ECU failures I noticed
>the hole in the air boot.
>
>-------- Original Message --------
>From: "Marc Boucher" <mboucher70 at hotmail.com>
>Subject: Re: Audi 100 Won't Start
>To: syljay at optonline.net, quattro at audifans.com
>
>Thanks for the step by step.  I think we're already at your step 8 :-)
>I've verified that there's a spark, and it WILL fire up occasionally and
>run
>for a few minutes.
>As far as step 8, here's what I've done so far:
>
>Removed fuel pump relay and shunted it.  Result: Fuel pump can be heard
>to
>run the same as when you first switch on the ignition.  Nonetheless no
>change in starting behavior.  Conclusion: Fuel pump relay is not the
>cause
>and I've removed the shunt and replaced the original relay.
>
>Note that since fuel pump can be heard to be running and is drawing six
>amps
>when shunted, is it a fair conclusion that fuel pump is ok?  My next
>test is
>to disconnect the fuel line at the filter, engage the pump and measure
>the
>flow but I'm hesitant to do this.
>
>One more bit of info: here is the car's current starting behavior:
>
>If you try to start it, 15 times out of 25 times (estimate) it will kick
>over and make you think its headed towards a healthy fast idle but
>abruptly
>die at about 1000 rpm. Perhaps 9 times out of 25 it won't even kick.
>And
>about one in 25 times, it will sputter to a fast idle, which might
>actually
>continue for a few minutes (but given that its in an underground garage
>I'm
>limited as to how long I can permit this).  Shifting it into gear or
>otherwise letting the idle drop to anything too far under 2000 rpm will
>make
>it die.
>
>If you disconnect the wire going to the cold start valve then not only
>will
>it not start but it won't even kick a single time.  I had thought that
>this
>valve simply gives additional fuel to make the cold start easier, and
>only
>supplemented fuel coming from the other 5 injectors.  Thus I'd expected
>at
>least one or two kicks without the cold start valve.  The car is in a
>garage
>whose temperature is about 10C (52F).
>
>Thanks again for your continued help,
>
>Marc
>
>
>
> >From: SJ <syljay at optonline.net>
> >To: quattro at audifans.com
> >CC: mboucher70 at hotmail.com
> >Subject: Re: Audi 100 Won't Start
> >Date: Mon, 26 Jan 2004 16:10:49 -0500
> >
> >1. Determine whether the problem is spark or fuel related.
> >2. Buy yourself one of those $7 in line spark testers.  It will flash if
> >you
> >have spark.
> >3. If you have spark, see if it will fire up.
> >4. The rubber air bonnet between the fuel dist and the throttle body has 
>a
> >few extra openings, which are plugged with a yellow colored plugs.
> >5. Remove one of these plugs. Substitue plug with hose or copper tubing.
> >6. Have someone crank the engine, Spray starter fluid into the attached
> >hose. See if engine will start and run.
> >7. If engine runs, spark and timing are ok.
> >8. Fuel related problems would be pump, fuel injection system, computer,
> >air
> >leaks, temperature sensor.
> >
> >Let us know how you did with above tests . . .then we continue to fuel
> >related issues.
> >
> >
> >SJ
> >85 Dodge PU, D-250, 318, auto
> >85 Audi 4k - - sold but still on the road
> >88 Audi 5kq
> >90 Audi 100q
>
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