McLaren started to put their miserable weekend behind them as Stoffel Vandoorne clocked 81 laps on the second day of testing in Bahrain.
Technical problems with the team's Honda engines stopped Vandoorne starting the race at the Sakhir circuit on Sunday and saw team-mate Fernando Alonso pull out shortly before the end.
Alonso, who will be replaced by Jenson Button next month in Monaco as he heads for the Indianapolis 500, publicly berated the lack of pace from his Honda engine throughout Sunday's race before his retirement.
McLaren test driver Oliver Turvey was only able to complete a handful of laps on Tuesday due to a water leak.
But that problem did not return on Wednesday as Vandoorne was able to make use of valuable track time on a day when Bahrain pole setter Valtteri Bottas set the fastest time.
The Mercedes driver, whose car stopped on the track in the morning session, completed 143 laps in total and clocked the best time towards the end of the afternoon.
Sakhir race winner Sebastian Vettel was second fastest after a late surge but mechanical issues with his Ferrari restricted the German to just nine laps in the morning. Garage system failures in the afternoon meant Vettel could only complete 64 laps.
Toro Rosso's Carlos Sainz, who took over from team-mate Daniil Kvyat at lunchtime, was third quickest with Vandoorne in fourth.
Haas driver Kevin Magnussen was fifth and Force India's Esteban Ocon set the sixth best time.