Fuel for days
 

This may be old news but the results were so awesome I had to post. Just did the rewire on a huge intank Apexi pump and found where all my fuel was going on the top of the rpm band ... low voltage was the culprit of my falling fuel pressure. I was able to pull out about 10% fuel from the upper regions now that the pump is keping up with the 19 psi of boost. Cannot believe I waited this long to do this mod!

I wired the stock 12v supply and gnd at the pump into the fuel pump speed relay that I pulled from the front of the engine bay. So with this relay located by the pump harness, I ran a high quality 12 gage fused power supply to the relay from the battery located in the rear bin and a 12 ga gnd cable from the bat. Then just pulled the pump harness connectors apart and used the factory spaded connections to attach to the relay (had to rewire the male spaded stock 12v supply and gnd to female to plug into the relay). Only takes a few minutes if I ever wanna put it all back stock.

You can also re-wire the stock relay to run ONLY 12 volts to the pump. That requires take it out from the front, opening the relay up, and pushing the tab over so it's always on....probably about a minute's worth of work.

Yea, forgot to mention that I had the speed relay bypassed for awhile before I did the rewire. Didn't help the high end fuel supply.

Before the rewire I would have 1.5 volts less at the pump than at the battery during idle conditions or running the pump off the battery with f/p-gnd trick ... after the rewire I had only 0.1 volts less at the pump.

I actually did your method probably about a year ago when I was having problems with dual pumps. I figured out that when you push the gas down, the car would start...but as soon as I took my foot off the pedal it would die. Figured I'd just run 12 Volts right off the battery(which is in the back) and it fixed all my worried!