1991 Canadian Grand Prix

As at the previous Grand Prix in Monaco, the pre-qualifying session was dominated by the Scuderia Italia Dallara cars, and the Jordans. With Dallara's Emanuele Pirro fastest ahead of his team-mate JJ Lehto, followed by Jordan's Andrea de Cesaris and Bertrand Gachot, there was over a second between the four pre-qualifiers and the rest.

Those who failed to progress to the main qualifying sessions included Olivier Grouillard, fifth fastest for Fondmetal, his best result of the season so far. The Modena team was starting to run into financial difficulties, and the performance of their Lambo cars was also slipping, as Nicola Larini and Eric van de Poele ended the session down in sixth and seventh positions. Slowest was Pedro Chaves in the Coloni, despite a new Hart-prepared Cosworth DFR engine.[2]

In practice Riccardo Patrese had a huge accident, walking away unhurt. In the qualifying sessions, Patrese took pole position from team-mate Mansell, out-qualifying him for the fifth straight race. Senna was third followed by Prost, Moreno, Berger, Alesi, Piquet, Modena, and Pirro.

At the start, Mansell got away well and led Patrese, Senna, Prost, Berger, and Moreno. Berger went out on lap 4 with electronics problems, while Aguri Suzuki retired when his Lola caught fire. Moreno was out on lap 10 when he spun off, while Prost was suffering from gearbox problems. The Frenchman had managed to hold on while he engaged in a battle with teammate Alesi and Piquet's Benetton.

Mansell led Patrese and Senna on lap 25 when Senna retired, leaving Mansell and Patrese a long way ahead of the Alesi–Prost–Piquet battle. This ended Senna's thus far perfect season. Prost retired shortly after with a gearbox failure on lap 27 and Ferrari's misery was compounded on lap 34 when Alesi's engine blew up.

The Williams drivers were now well ahead of the pack, but Piquet closed on Patrese, the Italian suffering from gearbox troubles of his own. In the late stages Patrese was passed by Stefano Modena in the Tyrrell. On the last lap, Mansell led from Piquet, Modena, Patrese, de Cesaris, and Gachot when he suddenly slowed to a halt at the hairpin. There were rumours that Mansell had failed to change gear for the hairpin and stalled the car, or that he had turned off the engine accidentally while waving to the crowd during the final lap. Mansell denied this, saying that the gearbox had gone into neutral as he shifted down, and Williams said that the car had suffered an electrical failure. This is technically true, but was induced by Mansell failing to keep the revs sufficiently high on the engine to drive the electrical and hydraulic systems, thus causing the gearbox barrel to get stuck. When the car was returned to the pits, the engine was re-fired and the gearbox worked perfectly.[3][4] Piquet thus took an unexpected victory for Benetton at the expense of his old rival Mansell, who was classified sixth. Jordan's five points, their first in Formula One, meant that they would no longer have to pre-qualify when the draw was reshuffled at the halfway point of the season.