After a somewhat troubled week of running at Jerez, Rubens Barrichello ensured that Williams' second pre-season F1 test ended on a high with the quickest time of the week in Spain.

The team had suffered issues with its rear wing and then with KERS through the opening three days of the test, while things weren't helped when Pastor Maldonado suffered an accident in his second day behind the wheel on Friday.

Having elected to run without KERS for the final day, Barrichello duly set the fastest time of the week with a best time of 1min 19.832secs - making him the only driver over the four days to lap below the 1min 20secs marker.

"We completed some long runs today and looked at trying some different things on the car," he said. "This morning was also the first time we could run a few new sets of tyres and get some momentum. The car performed as it should do so I am happy with that. The day went with minor problems, but we have some good direction and it is great to get some more mileage on the car."

A hydraulic leak was the only issue on the FW33 over the course of the day and technical director Sam Michael said the team would now work to resolve the problems faced in Jerez before the next test gets underway in Barcelona at the end of the week.

"Nothing was going to stop us from doing over 100 laps today!" he said. "After limited running up to now, we concentrated on setup and long runs. Rubens was trying various things to learn about the Pirelli tyres - some worked, some didn't. Now we've also gathered some data on the Pirelli wet tyre after a small shower at the end of the session.

"At the next test we will also have KERS back on the car as we ran without it today.We did suffer from a hydraulic leak during the middle of the day but overall, it's encouraging that we've had no major fundamental failures on the car - especially considering how tight the package is. All of the faults that have been causing our downtime in the recent days are small things that systems will quickly put right."

To view times from day four in Jerez, click HERE.