BARCELONA, Spain (AP) - Lewis Hamilton lost pole position over a rules breach on Saturday, giving Pastor Maldonado first place on the starting grid for what is shaping up to be another unpredictable Spanish Grand Prix.
Hamilton left it to his final flying lap to edge his Williams rival by more than half a second for what appeared to be his third pole of the season and McLaren's 150th overall.
But McLaren ordered the British driver to stop his car after crossing the line because of a technical glitch, with the team subsequently claiming their driver had insufficient fuel to return to the pits.
Governing body FIA ruled that "as the amount of the fuel put into its car is under complete control of (McLaren) the stewards cannot accept this" and Hamilton was "excluded" from qualifying results, allowed to start from last place instead.
"We told him to stop because we knew there was a problem," said team principal Martin Whitmarsh, who claimed earlier that Hamilton had had enough fuel left in the car for the mandatory sample. The rule was implemented following a similar problem with Hamilton's car at the 2010 Canadian Grand Prix.
The decision gave Williams its first pole since the 2010 Brazilian GP and made Maldonado the first Venezuelan driver to gain a top starting spot in F1.
Maldonado's lap of 1 minute, 22.285 seconds became the benchmark, promoting Fernando Alonso of Ferrari to the front two, while Lotus pair Romain Grosjean and Kimi Raikkonen were also in great position to earn the team its first victory of the season by filling out the second row.
"I'll do my best," Maldonado, the first Venezuelan F1 driver in nearly 30 years, said before learning of the decision. "I'm a fighter."
Ten of the last 11 winners at the Catalunya Circuit have started from the pole, and a Maldonado victory would make it a fifth straight different winner to open the season - which would make this the most varied start to a season since 1983.
Mexican driver Sergio Perez of Sauber was elevated to fifth in front of Chinese GP winner Nico Rosberg of Mercedes, while F1 points leader and two-time defending champion Sebastian Vettel starts seventh after opting to save his tires and failing to set a qualifying time.
After four races, Hamilton trails Vettel by four points following three straight third-place finishes. Mark Webber of Red Bull is five points behind his teammate, and Jenson Button of McLaren and Alonso trail Vettel by 10 points.