Engine problem thwarts Montoya

Montoya ended the day only 16th fastest, while his team-mate Ralf Schmacher spun twice in the first session, knocking his rear wing off in the second incident. He finished up 10th.

"During the second session I felt my engine was sounding strange so I went back to the pits," said Montoya. "The team tried to address the problem and then they let me out again to see if it had improved. But this wasn't the case so I had to pull aside on my out lap."

BMW motorsport director Mario Theissen explained: "We checked the data and we did a borescope examination, which allowed us to examine every cylinder with a camera drill. We could not find any anomalies and therefore Juan continued his training, but the problem was clearly still there and he had to switch off the engine."

Williams has often found itself off the pace on the Friday of grands prix this year and chief operations engineer Sam Michael did not appear to be too concerned by the problems.

"We had a difficult day in terms of looking for the set-up for the race," he said. "We made some progress but not enough, so we have quite a bit of work to do for Sunday. However we collected a lot of information and we know what the problem with the balance of the car is."