SAKHIR, Bahrain - Brazilian Felipe Massa put Williams on top on the penultimate day of Formula 1 pre-season testing in Bahrain on Saturday (Mar 1) while Red Bull's quadruple champion Sebastian Vettel failed to complete a lap.Massa, who moved from Ferrari at the end of 2013, completed 99 laps in his Mercedes-powered car and set the fastest time from seven days of testing at the Sakhir desert circuit."I'm really happy with the car and feel we found a good balance," said the 32-year-old, who carried out a full qualifying simulation on supersoft tyres towards the end of the afternoon."You can never be sure that you are 100% ready for the first race but I feel that what we have done in these days testing has been important for making sure that we have a car that can not only get to the end of the race but that will have good performance."'NOT THE BEST SITUATION'Vettel's car, however, broke down with an electrical problem on its first lap on Saturday. He tried again later but only made it to the end of the pits lane before stopping again. He helped marshals to push it back to the Red Bull mechanics, who diagnosed a leak that had also damaged other parts.Vettel, 26, said: "It's not the best situation to be in but we can't change it. Everybody is extremely motivated to fix it but it doesn't happen overnight. At this stage reliability is still a big question. It's difficult to say how long it will take to remedy."The season will start in Melbourne on March 16 and reliability is the key concern of teams facing the biggest technical upheaval in a generation thanks to the introduction of a new turbocharged V6 engine and energy recovery systems.'SMOKING POWER UNITSauber also had problems with its Ferrari-powered car on Saturday; Adrian Sutil managed only one lap before stopping with smoke coming from his power unit.While the four Renault-powered teams have had more problems than others over the three pre-season tests those using Mercedes power have put in hundreds of kilometres. Germany's Nico Rosberg did 103 laps in the works Mercedes with his fastest time 0.226secs slower than Massa's 1min33.258.Pole position for the 2013 Sakhir F1 GP was taken by Mercedes' Nico Rosberg - his time 1min32.330 - which shows the new V6 engines are up to the task.Ferrari's 2007 champion Kimi Raikkonen, who has replaced Massa, was third with 87 laps and Danish rookie Kevin Magnussen was fourth with 88 laps in a Mercedes-powered McLaren. Germany's Nico Hulkenberg, whose Force India also has a Mercedes power unit, did 115 laps.NEAR FULL-RACE SIMULATIONRenault-powered Toro Rosso and Caterham also had positive days; the former's Russian rookie Daniil Kvyat did 81 laps and the latter's Swedish newcomer Marcus Ericsson 117 - the most of any driver on Saturday.Ericsson ran nearly a full race simulation, including stops, in the morning before the session was halted by a red flag caused by another car stopping on track.The 23-year-old said: "The fact the car ran faultlessly all afternoon showed we'd pretty easily have finished a complete race distance and that's very good news for the start of the season." Stay with Wheels24 for the 2014 F1 season – fresh reports every day.