HEre is some more info on the fuel system. Note the last paragraph
http://online.wsj.com/article/SB1201...googlenews_wsj
Pilots and safety experts said both engines of the British Airways plane normally would have been draining fuel directly out of the same center tank during final descent to the field. Jetliners rely on additives to prevent ice formation inside tanks and fuel lines, but they don't typically have heaters to warm fuel. In the past few days, investigators have found internal damage to at least one fuel pump suggesting that the pumps weren't receiving adequate fuel flows, according to one person familiar with the details.