Audi 100 Won't Start

[Ado Sigal]

Marc, 
It sounds that you running only on cold start valve. Check if injectors are in place and seals are OK, with no play
around insert sleeves. Inspect CIS rubber boot and all manifold connections for correct seal. Take injector out, plug
the hole and observe if the fuel is being delivered (Try to operate the metering plate by hand while injector is out).
If the fuel is there and corresponds to the plate movement, you have definite vacuum leak. If there is no fuel, have a
look at the f/press. control valve 'O' ring on f/distributor head.
Since it happened suddenly, I would expect popped plug, injector, broken 'O' ring seal, tear in the boot and such.

HTH
Ado

-------- 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 behaviour.  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 behaviour:

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