drain gas tank

If anyone recalls...I did an engine swap on my blue gen1 prius since it was running badly missing,
and the toyota dealer told the previous owner it needed the head gasket replaced.
I was concerned when I did an engine swap, the swapped engine would also run badly, but it ran fine.
Until one day after I filled it up, it ran poorly again. And after the tank was run down a few gallons, it started to run smooth again. So I figured it must be the fuel cell and/or fuel pump.

As you might know, there is no replacing just the fuel pump, the entire tank has to be replaced.
I just happen to have an extra one from my original blue prius that got wrecked and I parted it out.

I also had the tank from the bluegeen one I made the video of pulling the motor from, I actually cut open that tank to see exactly what was inside, wanting to use the bladder inside for a race car. I made a video of that, but have not posted it (along with many others still not posted/finished..) but anyway, I needed to drain the fuel out of the tank. It isn't possible to just drain it out 'mechanically', it needs to have the pump run to pump it out.

So just in case anyone else needs to know, there is a big plug that goes into the tank with like 6 wires.
The fuel pump wires are the black (positive) and white(ish) (negative). This will pump the fuel out of the hose.

Here is a picture. Hope it helps someone, and I hope this fixed the 'can't fill the tank' problem..