Vandoorne: McLaren still has problems to 'discover' in F1 testing

An electrical problem stopped the Honda-powered MCL32 on track twice during Thursday's running at Barcelona, and the team opted to sit out the final hour as a precaution, leaving Vandoorne with just 48 laps to his name for the day.

With one day of testing remaining, Vandoorne said logging more laps consecutively has to be McLaren's priority.

"We've had our fair share of problems that halted our progress here in long runs," he said. "That's work we weren't able to do.

"It's always important to do long runs because there's many things you discover by completing a lot of consecutive laps.

"Now there's problems in the car that we haven't exactly discovered yet. A lot of our runs have been broken up.

"We don't know exactly how the temperatures will evolve over 50 laps or so.

"Those are things we hope to discover tomorrow, but at the moment we don't know what tomorrow will be like."

Vandoorne said after witnessing the progress McLaren and Honda made through the last two years, it was a surprise to see the partnership back in so much trouble.

"The last two years were difficult for us, but we've seen quite a bit of progress throughout which was encouraging," he said.

"Everybody came here expecting to see a big step forward.

"The problems we're facing now are probably a bit unexpected and it's not ideal, but this is the situation so we can't sit still and do nothing.

"We just have to work very hard and push everyone in the right direction.

"We gained some performance in the chassis, but also a little bit in the engine.

"It's clear that there's still a lot of work to do - where we stand compared to the others is extremely difficult to say."