engine cutout NG motor

[Mark Zvolanek <mzvolane@sydney.ipex.com.au>]

Gday to you all.
Thanks to all those who responded to my electric mirror enquiry. I am yet   
to fix the problem.
Something more urgent has occured yesterday. Yesterday was a very hot day   
~35'C or more.
My engine cuts out on a day's like this. This started happening about a   
month or so ago. Thinking it was the fuel pump I replaced it, week later   
I replaced fuel pump relay.
Now I don't know what could be causing it.
When the engine died I manually jumpered the fuel pump and I heard it   
going, but the engine still would not start, it was just turning over ...   
at least something. The engine temperature was not any higher normal.
So far I got stranded on four occasions, allways on a hot day 30'C and   
plus. Luckily allways I was able to roll off road , then after 10-15   
minutes the engine starts OK, and I can keep going. Its starting to drive   
me mad. I was fortunate enough not to get stranded on the Harbour Bridge   
also known as coat hanger, but there is always a possibility. :-)
Due to my lack of experience I now thing it might be something to do with   
fuel pressure, but I have no idea how to test for that. Or what else to   
check for.
Did anyone have any similar experience(s)?
Any help will be greatly appreciated.
Mark Zvolanek
1991 Audi 90 man,NG motor, non-Q