F1: Engine trouble for Sebastian Vettel puts Red Bull reliability in doubt

-- Could reliability be an Achilles heel for Formula One world champions Red Bull this season? If the first two days of winter testing are anything to go by the answer could be yes.

Four-time world champion Sebastian Vettel was stopped in his tracks by an engine failure after completing just eight laps in the new Red Bull racer Wednesday.

"We've not had a lot of running and have a few problems to sort out," Vettel told reporters at the Jerez circuit in Spain. "But with such big rule changes it is usual to have some teething problems.

"That's what tests are for, to sort those issues out. The next two days will be important to get some track time to prepare for the tests in Bahrain."

Vettel, who only managed three laps in the box fresh car on Tuesday, has now returned home to Switzerland and handed the keys of the 2014 Red Bull over to his new teammate Daniel Ricciardo for the remainder of the Jerez test.

Preseason testing is always a tense time but a major rule change has heaped extra pressure on the teams hoping to get their cars race ready for the opening Australian Grand Prix on March 16.