By Ian Ransom
MELBOURNE (Reuters) - Lewis Hamilton lent some credibility to the hype surrounding Mercedes by posting the fastest time in Friday practice at the Australian Grand Prix, as the Formula One season kicked off with teams still struggling with reliability problems.
The 2008 world champion could not finish a lap in the first session due to a sensor problem, but topped the timesheets in the second with a lap of one minute 29.625 seconds on a glorious sunny day at Albert Park.
Hamilton's quickest edged out team mate Nico Rosberg by less than 0.157 seconds as the pace of the two Mercedes' drivers carried on from their promising performances in winter testing.
Teams struggled to come to terms with the new turbocharged hybrid engines during the pre-season tests, and continued to battle glitches during practice, with drivers cooling their heels for long stretches in the garages, as technicians frantically tinkered.
Excursions onto the track saw a number battle to handle the extra torque and reduced downforce of the new V6 power units, with plenty of over-steering at corners and skids into the grass.
Ferrari's Fernando Alonso handled conditions better than most, posting the quickest lap of one minute 31.840 seconds in the first session and finishing third fastest in the second.
Reigning quadruple champion Sebastian Vettel battled a couple of nervy skids, coming onto the grass at one point in the later session, but finished an encouraging fourth, having endured a dismal winter testing with Red Bull.
His new team mate Daniel Ricciardo finished sixth fastest after putting some decent mileage into the car, with the Red Bull drivers sandwiching McLaren's Jenson Button in fifth place.
Kimi Raikonnen, in his first drive since returning to Ferrari, was forced to roll back into the garage after an aborted start at the exit of pit lane but re-emerged to post the seventh fastest time.
Hamilton was earlier left fuming when his car stopped at turn nine of his installation lap just five minutes into the first session.
With the vehicle hauled off by a tow-truck, the 29-year-old Briton walked back to the paddock without taking his helmet off and suffered the indignity of being stopped by security before retreating into his team's tent.
Mercedes later issued a statement saying they had fixed a "calibration" problem with an oil pressure sensor that triggered the engine's halt.
McLaren's Kevin Magnussen enjoyed the most positive day out of the three F1 rookies, posting the ninth fastest time in the second practice, but Caterham's Marcus Ericsson was unable to post a lap all day.
Japanese driver Kamui Kobayashi's F1 return with Caterham was also forgettable, as he failed to post a time in the first session and had to sit out the second as engineers worked on a fuel system problem.
(Editing by Patrick Johnston)