Starter "flat spot" - what's causing this?

[radek@istar.ca]

Thanks guys!

I took the starter out and counted the teeth on the flywheel:  lost track of the number 
but all are OK.  Next, I took the starter to the rebuilder who put it in a vise and
applied 
power:  worked like a champ.

I'm going to clean up all electrical connectors and the housing where it attaches 
to transmission, for good ground.  I'm also going to try to install some sort of 
heat shield on top of the starter to protect it from the exhaust manifold.  It sits
directly 
beneath and the original heat shield had rusted out a long time ago.
  
Hopefully, this will cure the problem.  Looks like it's not been getting sufficient 
amperage to operate, especially when hot (I understand the power draw will be 
greater when the starter is hot).
If all this doesn't help, it's rebuild time and it will be a different rebuilder.

Thank you for all for your help and support.

Radek
88 90Q
91 V8Q 5-sp.

> 
> Message: 9
> Date: Mon, 24 Oct 2005 01:23:25 -0400
> From: Huw Powell <audi at humanspeakers.com>
> Subject: Re: Starter "flat spot" - what's causing this?
> To: Radek <radek at istar.ca>
> Cc: quattro at audifans.com
> Message-ID: <435C6FCD.4090004 at humanspeakers.com>
> Content-Type: text/plain; charset=us-ascii; format=flowed
> 
> 
> > For quite a few months now, my 1988 90Q has suffered from this intermittent
> > problem.  Sometimes the car starts like a champ, other times you turn the
> > key and ... silence.   There is power draw (voltage drops) but nothing
> > moves, clicks or otherwise.  Total silence.  Push start.
> 
> If it's truly silent but you get a power draw, it's almost certainly the 
> starter.  In the meantime, the old trick is to whack it lightly with a 
> hammer to see if it will work on the next try.
> 
> > As a note, I found one way of dealing with the issue:
> > When the starter wouldn't work, I put the car into second gear and rock it,
> > trying to get the engine to rotate forward.  After such treatment it would
> > often start. 
> 
> That might have had the "hammer" effect - or, if you don't get true 
> silence but a click and whirring sound, you could be missing a few 
> flywheel teeth, as suggested.
> 
> > However, a strange, grinding noise persists for a few seconds
> > after the engine has started and then something disengages, everything
> > returns to normal.
> 
> That could be the starter solenoid thing sticking and keeping on the 
> flywheel after you release the key.
> 
> Prior to replacing the starter, I would use a test light on the starter 
> trigger wire to make sure it's not the ignition switch at fault.
> 
> -- 
> Huw Powell
> 
> http://www.humanspeakers.com/audi
> 
> http://www.humanthoughts.org/