Weird MC engine problem

[Phil Payne]

> > > Well, it must restart eventually.  How long does it behave like
> > not wanting
> > > to start?
> >
> > Variable - roughly two to five minutes.
>
> That's a bit fast for a fuel problem like flooding.

It's not flooding.  CO stays constant right to the end.

> > > When it will not start, does it have spark?  It might be a shorted coil,
> > > that kind of sort of works until the cylinder pressure goes up,
> > whereupon it
> > > shorts due to the increased heat load on the coil.  After it
> > cools, it works
> > > again.  This is, of course, a real WAG!
> >
> > Spark is normal.
>
> Hmm, still does not rule out a problem with spark under compression.

True.

> > > Have you swapped the ignition module for a known good one? (I'm
> > assuming the
> > > MAC-14 MC still has a separate ignition module, like the MAC-11 system)
> >
> > Yup - swapped the coil pack with another car.  Symptoms stayed
> > with the car.
>
> So much for the "short" (or "long") on the coil theory :-)

> > I forgot to mention - on a significant number of th efailed start
> > attempts, the engine kicks
> > in and runs backwards for three or four revolutions.

> Interesting.  Did you power wash the engine?  You may want to check the
> distributor, especially the cap.  I've seen water or other foreign material
> in the cap.  I've had these cars idle fine, but buck and stall under load or
> increased rpms.  Foreign material can cause all sorts of crossfire events,
> which might explain the backwards running, and the stall.

Nope.  No wash and the distributor has been out and cleaned so many times ...

The only oddity - at some time someone has scratched a 'new' alignment mark in the top of the
distributor body wall.  It's about 5 degrees advanced from Audi's mark.

> You're not off by one on the plugs, by chance?  Maybe swapped two leads?  I
> suppose it might idle in such a state, though I have not tried this.

Firing order is correct.

I should mention that the car is at a turbo specialist - Turbotronic in Woodville.  It has
every diagnostic device known to man hooked up to it.

--
  Phil Payne
  http://www.isham-research.com
  +44 7785 302 803