Ricciardo, who finished 5th in last year's drivers' standings, also topped the lap count with a mammoth total of 165.
"The auto breaking down, yes, it's testing, so we have some little issues which we have to fix, but it's just testing".
Ricciardo edged out Hamilton by 0.353 seconds for fastest time, but the Mercedes was substantially quicker when the cars were on equivalent tyres.
McLaren got Vandoorne out in time for three laps at the end of the morning; but his afternoon running was cut short by a hydraulics problem with just 38 laps to the MCL33's name. Times set in testing are not officially recognized as track records.
Boullier noted that problems will arise early on in McLaren's relationship with Renault Sport, after parting ways with former engine suppliers Honda late past year. Raikkonen was scheduled to be on the track in the afternoon.
Gigaba contradicted by Home Affairs on Guptas' citizenship
Ajay Gupta is regarded by South African authorities as a fugitive from justice after a warrant of arrest was issued against him. Apleni shielded Gigaba from the fumble he made publicly on Tuesday, reiterating that Ajay was not a citizen.
McLaren boss Eric Boullier insisted that he is not "overly concerned" about the problems. "It is part of the process", Boullier said.
While fastest man on course today, Ricciardo said Mercedes remained " top dog at the moment but I don't actually think we're far off". "This is testing, give us time - it is fine".
Alonso, who has said he expects his team to be able to challenge for podium positions this season, is due to speak to the media this evening.
The Australian's time of one minute and 18.047 seconds on the new hypersoft Pirelli tyres lit up the timing screens on the second day of the final pre-season test at the Circuit de Catalunya.
India vs Bangladesh 2nd T20I: India's Predicted XI against Bangladesh
India got off to a bad start as Dushmantha Chameera removed captain Rohit Sharma for a duck off the fourth ball of the first over. Sri Lanka , on the other hand, will also miss their skipper Angelo Mathews and Asela Gunaratne due to injury.
Alonso had briefly led with an early morning run on the hyper-soft tyres - his quickest time on that tyre was 1:19.856, though it was set in the cooler conditions of the early morning so can not be reliably compared to those set by Ricciardo and Hamilton later in the day.
Ferrari's Sebastian Vettel delivered the fastest time in Formula One testing yesterday morning (Singapore time) as warmer conditions greeted drivers in Barcelona following last week's snow-hit sessions.
"I will be in the auto, I will drive - hopefully we will keep discovering new things on the vehicle - but if Australia was tomorrow it's okay".
No problems for Hamilton and Mercedes so far at winter testing And potential title rivals Ferrari are putting in the miles, despite driver Kimi Raikkonen calling in sick early in the day "20 years of hurt".
Pitt Season Ends With 67-64 Loss to Notre Dame
Per KenPom.com, Virginia Tech is No. 33 in offensive efficiency and No. 8 in effective field goal percentage (57.8 percent). Buzz Williams has had success in the ACC Tournament at Virginia Tech, winning a game in each of his first three seasons.