In an electrifying atmosphere inside a jam-packed Belgrade Arena, the experienced French partnership roared back to win 3-6, 6-7, 6-4, 7-5, 6-4 and spark wild celebrations from their sizeable army of fans in a sell-out crowd.
Their victory put France 2-1 ahead in the tie and Gael Monfils could wreck Serbia's hopes of winning the trophy for the first time if he beats home favourite Novak Djokovic in Sunday's first reverse singles.
Nearly 17,000 fans waving flags and banging drums cranked up the volume throughout a stormy match that threatened to boil over at the end of the second set when Spanish umpire Enric Molina struggled to keep order.
However, it was the French duo who kept their composure at the crucial moments and Llodra's winning volley ended a pulsating match after four hours and 34 minutes to leave Serbia needing to win both of Sunday's singles rubbers.
On Friday, Serbia had lost their opening encounter but Djokovic, a huge favourite among the home fans, levelled proceedings in style.
Results: France lead Serbia 2-1.
On Saturday: Viktor Troicki/ Nenad Zimonjic lt to Arnaud Clement/Michael Llodra 6-3, 7-6 (7-3), 4-6, 5-7, 4-6.
On Friday: Novak Djokovic bt Gilles Simon 6-3, 6-1, 7-5; Janko Tipsarevic lt to Gael Monfils 1-6, 6-7 (4-7), 0-6.
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