Weird hot start problem with 1990 Coupe Quattro

[jallred@spdg.COM (John Allred)]

Greetings all:

I have an intermittent problem with my Coupe Q, which is driving me
and my repair shop bananas.  Me, because I'm dead in the water for
twenty minutes or so until the car starts again; the repair shop,
because they can't reproduce the problem.  The car has been absolutely
flawless up to this point.

The car has difficulty starting _sometimes_ while hot.  Cold start are
always fine.  Some hot starts are ok; some require attempts to start
for about twenty minutes before the engine catches. The starter and
battery are fine.  The longer the car is driven, the better the chance
of starting difficulties.  This problem cannot be reproduced by idling
the car -- the repair shop did this for hours with no problems.

I believe that I can hear the fuel pump relay clicking on for a second
when the key is turned (correct, per the Bentley manual); sometimes I
can hear a faint whine from the rear of the car, which I assume to be
the fuel pump.

My guesses as to why I'm having problems starting this car:

1.  the )$(#*&@ oxygenated gas -- it has been warmer in Seattle since
the problem first reared its ugly head.  The oxy gas should have gone
away on March 1st; so I should be able to test this theory pretty
quick.

2.  The fuel pump is intermittently dying.  It obviously doesn't work
as hard while idling than when it's running at freeway speeds.

3.  Some sort of vapor lock, cause unknown.

I'd love to hear any other theories.  Answers would be even better.  :-)
-- 
John Allred (jallred@spdg.com)
Stratos Product Development Group, Seattle, WA