Nico Huelkenberg of Force India has recorded the quickest lap on the opening day of the Formula One testing in Bahrain.
The 26-year-old German posted a time of one minute 36.9 seconds, a full second quicker than Fernando Alonso of Ferrari.
Lewis Hamilton was third, just a fraction further behind, while Kevin Magnussen of McLaren was the only other driver to break the 1 minute 40 second mark.
World champion Sebastian Vettel was fifth fastest over the day but his Red Bull managed only 14 laps, a meagre total in comparison to Huelkenberg (78), Hamilton (74) and Magnussen (81).
Adrian Sutil of Sauber topped everyone with 82.
Red Bull had made a slow start with over four hours of work being done on the RB10 in the garage before Vettel emerged.
The finish was not much better as smoke poured out the back of the car, suggesting the problems experienced in the Jerez test are far from solved.
Red Bull struggled badly in that first four-day test last month and failed to drive even 100 kilometres in total.
Red Bull team principal Christian Horner was seen discussing the situation with Renault engineering chief Remi Taffin before Vettel took to the track.
Taffin had previously said two or three big problems had been solved after the disappointment in Jerez.
Four-time world champion Vettel is scheduled to drive for the team on Thursday before team-mate Daniel Ricciardo takes over for Friday and Saturday.
There is a third and final test week in Bahrain which begins February 27 before the Australian Grand Prix opens the season on March 16.
