Rampf studied Automotive Engineering at the Munich University of Applied Sciences, and has worked as a development engineer for BMW since 1979. From 1989 to 1993, Rampf worked for BMW in South Africa, where he discovered Formula One.
The Sauber team made its debut in Formula One at the South African Grand Prix in 1993. Willi Rampf was invited to the race, and half a year later he signed a contract to become race engineer for the Sauber team.
Rampf was the engineer of Sauber driver Heinz-Harald Frentzen for three years. In the 1997 season, he worked for drivers Nicola Larini, Norberto Fontana and Gianni Morbidelli. At the end of the 1997 season, Rampf returned to BMW, where he would lead the motorcycle project for the Dakar Rally. BMW motorcyclist Richard Sainct would win that race.
At the end of 1999, Rampf returned to Sauber, where he became technical director on April 1, 2000. He remained in that position when Sauber was taken over by BMW in 2005, and when the company withdrew its backing in 2009.