Red Bull's pre-season struggles continued as the world champions endured a difficult third day of testing in Jerez.
The car broke down on its first lap in Daniel Ricciardo's hands after Sebastian Vettel
managed only 11 laps
over the first two days.
Ricciardo managed only two more laps before Red Bull called a halt to proceedings to try to fix the problem.
McLaren's Kevin Magnussen set the fastest time of the day.
Magnussen, who is making his F1 debut this season, was 0.424secs quicker than Williams' Felipe Massa, with Mercedes' Lewis Hamilton a further 0.252secs behind.
The second McLaren of Jenson Button made it four Mercedes-powered cars in the top four, with Ferrari's Fernando Alonso fifth, 2.219secs off Magnussen's pace.
But the times will be virtually meaningless, as the teams are only just beginning to learn about the most complex cars they have ever built.
Ricciardo's Red Bull had a breakdown on his installation lap after he had waited three hours to take it out
Formula 1 has new technical regulations this year that amount to the biggest change in car design for a generation.
introduced in a drive for efficiency
and to bring the sport into line with road-car development are immensely complicated and innovative 1.6-litre V6 turbos with extensive energy-recovery systems.
The teams also have to cope with new chassis rules that have significantly changed the aerodynamics of the cars.
With world champion Vettel having managed little running in two days in Jerez, Red Bull and engine partner Renault had hoped to get Ricciardo out on track early on Thursday.
But he had to wait in the garage for three hours in the morning while problems with the car's hybrid energy recovery system were fixed.
The car then ground to a smoky halt before Ricciardo finished his first lap.
Ricciardo went out again about half an hour later but by the mid-point of the day he had completed only two laps under the car's own power.
The team were later forced to call off any running on Thursday, making it a total of 13 laps completed by the car over three days so far.
"Adrian [engineer Newey] has gone back to the drawing board. There is only so much they can do here at the track," said Ricciardo.
"Adrian is pretty happy working in his office back at Milton Keynes and he'll definitely be getting involved in trying to sort out the next step.
"They assume it is something that will have to be sorted out at the factory but at the same time they are trying to get a quicker fix for tomorrow. They've worked nearly 36 hours on the car to get it running.
"Time is still on our side. Even if we go to Melbourne [first grand prix 16 March] still a bit whatever, it's a long season. These guys know how to win and I'm sure sooner rather than later we are going to get it together. It's still early days."
Red Bull race engineering co-ordinator Andy Damerum added: "It's obviously not where we want to be and naturally the whole team is frustrated by these issues.
"However, we're pretty good at bouncing back from this type of thing. This is where the whole team pulls together and I'm sure we will get these problems fixed."
Red Bull owner Dietrich Mateschitz (right) talks with team principal Christian Horner
Red Bull's junior team Toro Rosso, who also have a Renault engine, were unable to run at all on Wednesday and continued to struggled on Thursday, as did the third Renault-powered team Caterham, who were unable to set a timed lap.
The lack of mileage for Renault-powered cars compared to those of rival manufacturers Mercedes and Ferrari continued a trend since the beginning of the test and is a major concern for the French company.
Alonso, cheered on by hundreds of fans in the grandstands at the Jerez track in southern Spain, also suffered a breakdown mid-morning, before resuming running a little later on.
German Adrian Sutil crashed his Sauber in the afternoon.
The back-of-the-grid Marussia team finally ran their car during the afternoon, after delays getting it to Jerez.
The test concludes on Friday, after which there are two further four-days tests in Bahrain next month before the start of the season in Australia on 16 March.