STR, Williams rule out rig failures

Both teams suffered brief fires during pi stops at the Hungaroring, as Honda also encountered flames at one of their stops.

Although Honda put their incident down to the refuelling hose not being fitted squarely on the car, there was initially some uncertainty about the causes of the other fires.

However, Williams believe that their problem was caused by the fuel pressure in the heavily-filled tank causing excess fuel to bubble up inside the hose, while Toro Rosso are not willing to comment beyond confirming it was not a fuel rig problem.

Rod Nelson, Williams' chief operations engineer, told his team's official podcast: "We planned a two-stop race but put enough fuel in so we had the possibility to go one stop.

"And on the basis of (David) Coulthard's performance against Webber, Coulthard started on the option tyre, we decided to go for it. We were nowhere by that stage anyway because of problems at the start, so we went for it with Kazuki, which meant we were putting a lot more fuel in the tank than you normally would, certainly (for Hungary).

"It was very hot, so fuel was vaporizing at a massive rate - and that causes some foaming within the fuel hose. You get fuel up the vent hose and some of that splashed down into the car connector just as they took the rig off.

"As soon as you drive out that splashes over the exhaust system and you have a small flash fire."

A Toro Rosso spokeswoman said: "I can confirm it was not a problem with the rig. The problem has been resolved to make sure it does not happen again, but there is no further comment from our technical group."