While Sebastian Vettel soared to yet another pole position, Mark Webber experienced yet more problems with his KERS unit aboard the sister Red Bull.
"It's hard knowing you're losing time on every straight," said the Australian, four tenths down in qualifying after missing the entire third practice session with the failure.
Earlier, it emerged in Montreal that Red Bull's KERS in 2011 is deliberately designed to be smaller and therefore less powerful than the leading systems, in order not to compromise Adrian Newey's aerodynamic design requirements.
But it has caused problems, and Australian Webber is expecting more of them on Sunday.
It's totally unpredictable
Asked if his mechanics will be able to fix the unit before the Canadian Grand Prix, he told Auto Motor und Sport: "It will be tight. The boys will do whatever they can.
"It's totally unpredictable. Sometimes it's very good and we have it under control, then we don't. It's a big challenge for us and costs us a lot of (lap) time when there are problems."