Champions Mercedes managed only six laps by lunchtime due to a gearbox problem while McLaren’s new signing Daniel Ricciardo set the pace in Formula One’s first pre-season test in Bahrain on Friday.
The Sakhir circuit is hosting three days of testing before the opening race in the Gulf kingdom on March 28.
“Going to have to keep you waiting a little longer for a proper look at W12,” Mercedes said on Twitter.
“We have a gearshift problem and are swapping the gearbox to get back out on track for our first real run. Better to have this lap one of testing, rather than lap one of race one.”
Mercedes, chasing an unprecedented eighth successive title double this year with Britain’s Lewis Hamilton aiming for his record eighth, were last on the timesheets.
Hamilton was in the car for the afternoon, when a sandstorm blew in to make life more difficult.