JEREZ, Spain - McLaren gave its rivals something to chew on as Jenson Button kicked off Formula 1's pre-season testing with a lap time comfortably quicker than his rivals.Button's first day back in the cockpit was much less dramatic than his 2009 championship year with Brawn GP, when his car was a half-second quicker than the rest on its first lap out of the garage. He still set the pace despite a fuel-pump problem.FEELGOOD TESTINGButton, who won the season-ending Brazilian GP as well as the 2012 opener in Australia, completed 37 laps with a best time of 1min18.861, 0.848 quicker than the fastest time set by Red Bull's Mark Webber over 73 laps.It was also nearly two seconds faster than Mercedes, which will have Button's former McLaren team mate Lewis Hamilton in a car. Mercedes' test session was cut short by electrical problems.Track test times are often misleading and largely meaningless, with teams performing routine systems checks and running through different programmes with varying amounts of fuel. They do carry a feelgood factor, though.Ferrari's Felipe Massa, only sixth fastest in the new F138 that the Italian team hopes will banish the memories of its 2012 car, certainly noticed. He said: "The 18.8 is an incredible time definitely, but the 19.7 (Webber's time) I don't think so." Webber, whose triple World champion team mate Sebastian Vettel will not be driving until February 7, agreed the McLaren had made a statement. "Yeah, it's a strong lap time. I don't know what tyre compound he was on or what was going on but it's certainly not a slow lap around here - 18.8 at Jerez on Pirellis is a pretty handy time."MORE WORK TO BE DONETo put it into perspective, only three drivers were quicker over the four days of testing at Jerez in 2012 compared to Button. He said he was not about to get carried away, as the fuel-pump failure after three laps cost him precious time. "In terms of the feel of the car, it's a nice starting point but not the mileage we hoped for on the first day of testing. There's nothing that stands out where you think 'Wow! That is something we have to work on', so it's a good base," he said.Inevitably, only hours after the wheels had turned for the first time and with two full tests to come before the season starts in Australia on March 17 2013, Button was asked whether it was a championship-winning car.Button answered: "Who knows? The important thing is there is a nice feeling with the car. Lap times mean nothing right now, and they won't mean anything at the last test."Romain Grosjean was third fastest for Lotus, ahead of Force India's Paul di Resta and Daniel Ricciardo next on the list for Toro Rosso.MERCEDES ON FIREMercedes had Nico Rosberg on track only for 14 laps before he stopped with flames momentarily flaring at the rear of the car. The team blamed a wiring loom problem. The team was fifth overall in 2012 and has struggled to impose themselves since taking over Brawn GP in 2009 but Rosberg sounded positive that the car was a step up.Rookie Max Chilton was at the bottom of the time sheets after his day was cut short by a rear suspension failure hours after the new Marussia had been presented to the world."Something gave way," he said.