I tried to settle this argument one way or the other last night buy performing some experiments of my own.
I took a 04 plate Vauxhall Corsa, disconnected the fuse for the fuel pump then ran the vehicle until it stalled, spun it over some more to confirm that I'd drained the remaining Unleaded from the fuel lines.
Next I took a 24mm hole saw and, at the lowest point drilled a hole in the fuel tank. The remaining thirty or so litres spilled into the readied paper bag I had carefully placed under the area I was to drill. Putting that to one side so as not to waste any for after I'd finished my experiment I then wheeled the Vauxhall into the Farms workshop.
I used my new Dyson hoover (with antibacterial filters so that I could keep my project as controlled as possible without risk of contamination from "rouge" elements) to suck the remaining fuel vapor from the 24mm hole in my tank. Quickly realising my mistake I removed the filler cap and continued my efforts from the top side (fuel vapour is lighter than air so hoovering from the bottom of the tank would have only removed half of the remaining vapor)
Using a section cut from the bottom of a fiberglass rowing boat and some clear silicone sealer (I didn't want my experiment to be affected buy the colour of the White bathroom sealant that was also readily available to me) I covered the hole in the bottom of the tank.
Next I carefully measured and cut 6.5 meters of common garden hose, fixing a female connector to one end and the male to a metal tap at the back of the workshop. I then connected the hose to the wall at one end and fed it down the filler neck of the vauxhalls fuel cell at the other. Being careful to disconnect the battery first so as not to risk a fire! I proceeded to fill the vauxhall with 45 liters of normal tap water. I replaced the fuel cap, connected the battery and slid into the drivers seat brimming with the anticipation of my results and cranked the key.
6 hours and 10 batteries later I still hadn't managed to start the car, proving once and for all that I don't have the knowledge skills or tools to be testing any type of scientific theory in my shed, and now I need a car.
Moron out!