I think it helps to take the confusion out of the system if you look at the fuel panel as the schematic drawing that it actually is.

Each section (ENG 1 - left, ENG 2 - center, ENG 3 - right) is schematically drawn with the tank (represented by the gauges labeled NO 1, NO 2 & NO 3 TANK) in the middle. Follow the lines from the tank and you'll see the flow of fuel. It is drawn to the pumps, then through the LOW PRESS lights (OFF if the pumps are ON) to join up immediately prior to flowing through each respective Fuel Shutoff valve to the engine. The engines in the picture are where the ENG 1 / 2 / 3 label is, right below the shutoff valve. There are even small arrows on the lines between the low press lights and the shutoff valves indicating direction of flow.

As Mark stated, in normal operation with equal fuel in all tanks, the switches are set for tank to engine operation and the #2 Fuel Crossfeed Manifold valve stays open to keep the Fuel Crossfeed Manifold pressurized. Looking at the schematic while feeding all engines from the center tank, you can see that with the #1 & #3 AFT and FWD Boost Pumps off, the only way the left and right engines get fuel is through their respective Fuel Crossfeed Manifold valves, which will be open.

I'm pretty sure that in the real airplane, there is no need to switch off any pumps to feed all engines from the center tank, as the four pumps in the #2 system run at a higher pressure than the ones in the #1 & #3 systems, so basically overpower those to feed fuel to the outboard engines. It's been a very long time since I flew the airplane though, so in order to prove that I'd have to dig through a mound of manuals in the garage...or just wait for Lou to confirm, deny or clarify ;)