Activating a pump via an oil pressure switch.

[Rumcajs]

Im wondering if i have a wire in the loom somewhere thats only powered when the engine is running. Then i could use this to switch the relay on.

There is. You could use alternator return signal to charge lamp (it goes 12V+ when alternator is charging) this feature is commonly used to run "alternator charge relay" in heavy vehicles. You could also include oil switch in to that circuit and that way you would have best of both worlds. ..... Indeed that's how subtank fuel transfer pump module is controlled/operated.

Also it would benefit everyone if you keep the line of communication on this public aka in this thread, I'm sure there are many who'd like to know how this can be done.

Cheers