The relay operating the fuel pump is the DME relay. It is actually a two coil relay. Once the DME senses crank rotation the second relay closes to power the fuel pump.
This is from a Porsche 911 book.
There is also a long article at
Clarks-Garage.com its for a 944 but I think most if not all applies to the 964.
I always have a spare DME relay in my car as they are notoriously troublesome