Jack,
Does the external fuel pump even work? My experience, especially since the advent of Ethanol additives, is that the fuel pump will not work after sitting for an extended period of time. (Note: these cars like to be driven and driven hard.)
You will need to make yourself a relay jumper from a piece of wire and 2 crimp on spade connectors. (I also put a switch in mine to easily turn the power off and on as I need it)
Download the relay/fuse chart for your model year car from
928 SPECIALISTS ONLINE STORE - 30,000+ 928 Parts - 928 SUPERCHARGER KITS!. You're young and will find it there. If you were older, I would probably have to direct you a little more.
On the chart, it will tell you which relay is the fuel pump relay. Pull that relay from the Central Fuse panel. Look at the relay. It will have a diagram that corresponds to the male spade terminals on the bottom of the relay. If you look closely at the bottom of the relay next to the spade terminals, you should see numbers such as 30, 86, 87 etc. Install one end of the jumper that you have made in the female terminal on the Central fuse panel that corresponds to the relay terminal 30. Install the other end of the jumper wire to the female terminal on the Central fuse panel that corresponds to the relay terminal 87.
This will complete the circuit for the fuel pump and the fuel pump should begin pumping regardless of the key position. You should hear a hum or a sound from the rear of the car. The jumper will give you time to go to the back of the car to listen closely and you may even use your hand to feel the cover for a hum if you can't feel it.
Make sure that you remove the jumper wire when not using it to test the fuel pump!!! The fuel pump will continue to run and pump fuel until you remove the jumper wire. The normal relay and key operation only runs the fuel pump for about 3 seconds if the car doesn't start. (Its a safety feature in case of crash) But 3 seconds is not enough time to hook up and run to the back to check the operation. That's why I suggest a jumper.
Honestly, I will be surprised to hear that your fuel pump still works after sitting for so long, but I'm wishing you luck.