Starting Problems (electric and rather interesting)

[evangelo@mecf.wustl.edu]

Hi everybody,
I hope you had a good Christmas Break. Unfortunately I had to spent it without
my Audi. It was in the mechanic. Here is my story:
I had some problems starting it when it was hot. The car would start fine
when cold (or so I thought), untill one morning decided didn't want to
go to school and stayed home (engine cold). When I returned I cranked the 
engine and it started at once. I spent some time looking around, sent a letter
here, looked at some things, but found nothing obvious or in beginer's level.
I got it to my mechanic. He found that fuse no. 13 sometimes had and
sometimes had no power. Therefore sometimes the fuel pump would
go on, sometimes not. He jumped the fuel relay, but again sometimes it would 
start and sometimes not.
After two hours of labor I stopped him. His suggestion is to go to the
dealer, which I would like to avoid.
So far we know, it's not the fusebox, nor the ignition switch. 
Are there any other suggestions from the net ? Anything I could check
or have him check ?

Thanks
Evangelos
(that's on a 5000 '86 CS Turbo).