Buildcraft pump mechanics

[gummby8]

I can't seem to figure out what it is about the buildcraft pumps that makes them not drain lava when in the nether.

I can put a pump in a sea of lava in the nether and it will never drain the source blocks, it will pump lava infinitely to a geothermal gen. But if I make a small pool of lava say closer to my nether portal, so I won't have to walk as far, it sucks up the source block.

Is it a altitude thing? Pumps wont suck up lava in the nether if under a certain altitude, or do I have to make the pool of lava bigger? The pump I have in the sea of lava is right on the shore and it is only 1 block deep.

[MechaCrash]

The pumps working the lava sea are, in fact, draining source blocks. It's just that it's draining source blocks farther out before it gets the ones closer to the actual pump. If you look around a bit, I'm sure you'll find an area where the lava is flowing and looks like it's been disturbed. That's the work of your pump.

You can eventually drain the Nether of all of its lava, but it'd take a lot of time and pumps to do it. It's like dirt: not technically infinite, but probably more than you'll ever need.

[gummby8]

EDIT: You are correct, after searching farther out (over 70 blocks out) I did see source blocks getting used. I didn't expect the pump to draw from anywhere in the entire source but apparently they do