Questions on draining fuel tanks

[V12diablo]

In my attempt to drain all the old gasoline from my 356 AC I have purchased a electric fuel pump that pumps at 3 psi, it says it can be used as a lift and transfer pump. I created a wiring harness that keeps everything safe so there is no sparks produced and the switch is outside the salon. The issue I have is the pump would not pull the fuel from the fuel line going to the engine, I had to unscrew one of the plugs on top of the port and starboard fuel tanks and put a hose down in to pump out the fuel. I pumped aprox 50 gallons from each tank. Is the pump not strong enough to pull fuel through the antisiphon valve? I have drained the 2 main tanks down to about 1/2 inch of fuel, is there a way to get it all out, I do believe there is water in the tanks that I would li,e to get out. If I have to drain the aux tank the same way will there be a plug that is accessible by going through the rear stateroom access?

Thanks in advance,

Jason

[tomschauer]

If it an actual fuel pump it "should" be able to open the anti siphon valve it is able to pull a vacuum.
Some pumps aren't. Maybe post the specs.
you should also have a screen on the pick up tube in the tank feeding the anti syphon valve, if you got a lot of nasty stuff, that could be clogged.

[Dad Joke]

I'm doing the same project. Buy a sink supply pipe at Lowe's or Home Depot and cut the fitting(s) off the end(s). Insert the tube into the end of your pick-up hose. Unmount the tank so you can tip/tilt it toward the port that you opened. Then stick the tube down into the lowest point of the tank and pull out the last of the fuel.

[km1125]

Many electric pumps do not have very good suction, and not enough to overcome an anti-siphon valve. There are some that can, but you have to look for those. That's why most electric pumps just have a screen before them and the filter after the pump.

[buster53]

Ok, I had fuel issues in my 356 as well. I paid a fuel polishing guy to come pump my tanks. I had a lot of water in my tanks. He removed the fuel level sending units and pumped from those openings. Good luck getting to your aux tank. We didn’t but then I was pretty sure that tank was still in good order.

[g36]

I do know this works and I have done this on my 405 and trojan. Might just be the pump is not strong enough like mentioned earlier. Probably won't get all out because you probably can't loosen the tank enough with the engine room limitations