200QA suddenly no start, no spark - Solved!!!

[David Michael]

At lunch time I checked that the b+ (track 15) was 12V and it was. So then
I temporarily hooked up my old coil (one connector, high tension lead and a
ground clip) and the car fired right up.

"course when I went to install the old coil more permanently,
I totally forgot that the nuts on the back side of the firewall (in
the plenum) are NOT captive, and they fell off and rolled under the
blower. Fortunately we have a metric screw cabinet at work..

While I can't be sure its the actual cause I suspect that, as a few folks
had postulated (along with Scott M's website), the transistor triggering
unit went bad. Ironically, it's a new unit I
installed prophylactically about 4k miles ago. Infant mortality.....

BUT, I  this is the last straw. It's time for her to go. I no longer have
time to keep up.  Car runs like a freight train, but needs some peripheral
work (window lifts, A/C, etc) and I no longer have time and don't want to
spend the money. Anyone have any idea what a 200QA with 235k that is running
extremely well but needs work is worth?

Thanks again to everyone for your help with this, and many other
problems.....

Dave



On Sun, Mar 21, 2010 at 8:14 AM, David Michael <adavidmichael at gmail.com>wrote:

> Thanks for all your suggestions. Based on what you all have said, I need to
> back the diagnosis up a step and 1st make sure the coils is powered. SJM's
> website suggests that it if the ignition switch can fail and stop powering
> the ignition circuit of the ECU.
>
> In any case, I will check 12V and use my LED tester to verify that the ECU
> is sending coil triggering pulses to the coil. Though it will have to wait
> till Monday - car is still sitting in the parking lot at work
>
> Folks on this list are great. Only way I could have gotten to 230k....
>
> Dave
>
>
> On Sun, Mar 21, 2010 at 3:17 AM, Huw Powell <audi at humanspeakers.com>wrote:
>
>>
>>
>>  If what you mean is the coils don't fail that much, but the POS
>>> (transistor) does, then
>>> that is correct.  The problem is probably not the coil itself, but the
>>> Darlington
>>> Transistor that is mounted on the coil, but generally the assembly is
>>> referred to a the
>>> coil by most
>>>
>>
>> The transistor failing is not the coil failing.  Coils are incredibly
>> simple.  Measure both sides.  Good?  then good.  I'm running an old audi
>> coil on my '57 Trojan loadster.  Made homemade ballast resistor.  Works
>> great.
>>
>>
>> --
>> Huw Powell
>>
>> http://www.humanspeakers.com/audi
>>
>> http://www.humanthoughts.org/
>>
>
>