In tank pump wiring

Having gone through 3 main fuel pumps on my 86  Cabriolet 1.8 DX engine with KJet, I decided to investigate why. It turn out the in tank lift pump is never running. I removed the in tank pump and checked it on the bench with 12 volts and it runs fine. On testing for power at the connector under the rear seat that feeds said pump I can’t find 12 Volts on the centre pin of the 3 pin connector which I assume is the pump power feed - the other 2 pins being ground and fuel gauge I assume. Where does the centre pin of this connector run from? I think it’s coloured Red/Orange or possibly Red/Yellow. For info I’ve fitted a new tank, filler pipe and swirl pot as I suspected there was a fair bit of rust and mud in the old tank.

It gets it's power from the main pump.