McLaren Team Principal Andrea Stella has revealed a fuel system issue was a contributor to Lando Norris' early downfall in Mexico City Grand Prix qualifying.
The Briton will start the race from only 19th having failed to set a representative lap in Q1, bringing an end to a strong run of form in his MCL60.
Norris initially ventured out onto the Autodromo Hermanos Rodriguez circuit on a set of Medium tyres but aborted and returned to the pits at the end of his first flying attempt.
When returning to the track on a set of Softs, a mistake in the middle sector left him significantly off the pace and left just one more opportunity.
But a spin for Fernando Alonso at Turn 3 triggered yellow flags and forced Norris to slow, taking away any chance of advancing.
Viewed by others:
McLaren take prudent approach
Norris was initially confused as to why he was told to abort his Medium tyre run at the start of the session but explaining an issue forced McLaren's hand, Stella told media including RacingNews365.com: "We had uncertainty on the fuel system that we needed to check.
"Therefore we decided to call the car in, have some time to check and then be ready to go on the final run on Softs, which in any case would have been the decisive run.
"So we thought rather than taking the risk that the problem actually forces us not to do the run on Softs, we just wanted to take the prudent approach and pull the car in."