SAKHIR, Bahrain - Formula 1 teams began their final pre-season test in Bahrain on Thursday with champions Red Bull and engine partners Renault still struggling as Mercedes-powered rivals racked up laps.Australian Daniel Ricciardo, Sebastian Vettel's new team mate at Red Bull, started off with a promising 32 laps in the morning but an attempt at a longer run in the afternoon was aborted.'WE'RE GETTING THERE'He told reporters the team was still playing catch-up after a difficult first two tests in Spain and Bahrain: "We're definitely not up to scratch with where we'd like to be in terms of programme."It's clear we probably won't come out to Melbourne and dominate as the team did in 2013 but it's still very early to say. We're getting there. The morning was definitely better and we definitely made a step forward in terms of power."With the season starting in Melbourne, Australia, on March 16 the four Mercedes-powered teams - Mercedes, McLaren, Force India and Williams - have looked well ahead of the four using Renault engines.The works Mercedes team of Lewis Hamilton and Nico Rosberg alone completed 3073km over the first eight days of testing in Spain and Bahrain while the four Renault teams together managed only 4019km.The Red Bull crew spent much of the afternoon in their garage before Ricciardo, who has replaced fellow Australian Mark Webber, managed seven more laps.Red Bull's race engineering co-ordinator Andy Damerum said the afternoon run had been stopped short when the sensors reported issues that turned out to be a problem with the exhaust.Only Mercedes-powered teams carried out race simulations before the final test with four times F1 champion Vettel's Red Bull risking heading for Melbourne without having run a race distance at one go.PEREZ FASTESTMexican Sergio Perez (Mercedes-powered Force India) was quickest on Thursday 1min35.290) ahead of Valtteri Bottas (Williams), also powered by Mercedes.Bottas put down the most distance - 128 laps of the 5.412km circuit compared to Perez's 105 - with a race simulation in the afternoon as well as tyre work for Pirelli, all without a problem.Rookie Kevin Magnussen also had a productive day in his Mercedes-powered McLaren - 109 laps, including a full race distance, and the sixth-best time.Ferrari had Kimi Raikkonen third on the time sheets with 54 laps under his belt. Renault power filled four of the bottom five places with 145 laps between them; Mercedes rivals did 431Kamui Kobayashi did the fewest (19) for Caterham while Venezuelan Pastor Maldonado, who left Williams at the end of 2013, managed only 31 for Lotus before being sidelined by problems with a new exhaust.Maldonado said: "It wasn't what we wanted but we're all working very hard to make progress. I'm sure we'll have solutions quite soon as a team."It's clear we have good potential and the car is not bad."Renault F1 deputy MD Rob White said after the previous test that the his crew had made progress but were some weeks behind where they had wanted to be."We are not back on schedule but we are moving in the right direction," he had said, adding that people at the factory were "working night and day to solve our problems". Stay with Wheels24 for the 2014 F1 season – fresh reports every day.