Hey bud, I've been doing alot of searching just lately on google cause my fuel pump stopped priming the other day, after much testing with a volt meter today, its very possible that the fault is with the Crank Position Sensor which tells the ecu how fast the flywheel is spinning and also supplies a current to the pump then the ecu tells the pump to start up and affects the timing and general running etc. There is also a fuel cut off switch in the bootwell that cuts off the fuel pump, have you pressed this in? Mine has been playing up a bit lately, i also put alive feed to my pump and it should have primed up but had no effect, if the cut off switch is faulty then you need to unplug the plug and test it, there should be a earth from one which comes from the fuel pump and a live which is sent from the relay/s. I think that brown wire your talking about goes to batt neg, this also controls part of the fuel system, it goes to the ecu which then sends a live feed to the pump, this has to have a good connection on the battery. Hope this helps you.