Possible to syphon fuel out?

[spannerrash]

Hi all
Due to life and waiting for spare parts issues I find myself in a situation where I have my S8 with a full tank of 1 year old petrol. I did use "Stab oil" when I filled the tank but am now not really anticipating using the car until spring so was thinking of draining the fuel and using it in my little fiesta. I could then refill the S8 with fresh fuel.

I know most, if not all modern cars have some kind of anti syphon system but was wondering if there is an easy way to get the fuel out?

Thanks Frank

[MikkiJayne]

The D2 does indeed have an anti-syphon filler neck. The best way I have found is to use the pump to push it all out for you, although that does mean you need to acquire a threaded adapter to connect to the fuel line at the front. I can't remember the thread sorry - M12x1.5 or something like that. I've got a hose tail of the right size attached to some ordinary braided hose so I can just hook it up and power up the pump. The advantage of using the pump is that it'll also empty the left hand side of the tank which other methods won't.

Alternatively, pop the level sender out of the pump assembly and you can syphon from there.

[spannerrash]

OK, thanks for that MJ.

I was unsure if running the pump constantly to empty the tank would damage it.

[spannerrash]

Hi all again.
Sorry to bring this back up again but I just have a couple of questions if anyone can help me out.

Does the fuel pump run constantly when the engine is running?

Does the fuel pump modulate its output at all during periods of low fuel demand?

I realise this is a return (excess fuel) to tank system but it just seems wasteful if the car is running at low load for an extended period of time for the pump to be running at full pelt constantly.

Obviously I could be missing something really fundamental.

Thanks Frank

[MikkiJayne]

Yes, it runs constantly with no clever control strategy. The pressure regulator on the fuel rail adjusts the pressure by bleeding off whatever fuel it doesn't need. Pretty much everything pre-FSI works like this. I would expect the pump load to be fairly constant since its pushing against a constant load of 4 bar. The regulator will adjust flow between the rail or the return.

The C5 RS6 is the only port-injection engine I know of with a PWM-controlled fuel pump. It uses the stock C5 in-tank pump as a lift pump and then has a high-performance pump in-line on the way to the engine.

FSI engines seem to use this PWM method pretty much across the board as far as I know.

[spannerrash]

Thanks once again MJ, much appreciated.