Jenson Button topped the first day of testing for the new formula one season in Jerez today, but not without problems for his McLaren.

The 2009 champion was 0.8 seconds faster than nearest rival Mark Webber in a Red Bull.

He set the time on hard tyres 10 minutes from the end of the session but endured a tough morning, with his car coming to a halt after just three laps.

The team said the problem was caused by a fuel pump, the same problem which stopped Lewis Hamilton while leading the Abu Dhabi grand prix last year, even though the design of the fuel pump has since been changed.

Button stopped the clocks at 1m18.861s.

Romain Grosjean was third in a Lotus with a 1m19.709s followed by Force India's Paul di Resta fourth, Toro Rosso's Daniel Ricciardo fifth and Felipe Massa sixth in the Ferrari, down 1.6s down on Button. Massa said the car so far was on another planet compared to the problems in testing last year.

Mercedes led early in the morning but their day came to an abrupt end when flames were seen at the back of the car.

The team said it will adjust a wiring loom before Lewis Hamilton takes over tomorrow.