Audi 100 Won't Start

Marc Boucher mboucher70 at
Mon Jan 26 18:55:15 EST 2004

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,


>From: SJ <syljay at>
>To: quattro at
>CC: mboucher70 at
>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 
>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, 
>leaks, temperature sensor.
>Let us know how you did with above tests . . .then we continue to fuel
>related issues.
>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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