On the right side of the engine compartment are two relays (near the battery). The front one (left in the pic) is the fuel pump relay.

The prime and run functions both happen through this relay. If you can go back and have the prime working that's good.
The yellow wire is attached to terminal 87.
The red wire is attached to 30/51.
The white wire on the block connects to 85. (there is a second wire in the block connecting to 86)
When you turn on the ignition the pump should run for approx 2 seconds. When the car turns over and starts, it will run continuously. These functions are generated from the computer.
The Volvo Sports America Fuel Injection book is good for testing this. Someone here found one recently. http://img196.imageshack.us/i/vsafihandbook.jpg/
If you really want to study the wiring diagram...
http://volvo1800pictures.com/document/ES73%20Wiring%20digram/73%20Wiring.jpg
which shows a green wire to 30/51...?

The prime and run functions both happen through this relay. If you can go back and have the prime working that's good.
The yellow wire is attached to terminal 87.
The red wire is attached to 30/51.
The white wire on the block connects to 85. (there is a second wire in the block connecting to 86)
When you turn on the ignition the pump should run for approx 2 seconds. When the car turns over and starts, it will run continuously. These functions are generated from the computer.
The Volvo Sports America Fuel Injection book is good for testing this. Someone here found one recently. http://img196.imageshack.us/i/vsafihandbook.jpg/
If you really want to study the wiring diagram...
http://volvo1800pictures.com/document/ES73%20Wiring%20digram/73%20Wiring.jpg
which shows a green wire to 30/51...?