I do know that I drive torque, while listening to my friends prattle on about horsepower.
The spring could be the culprit like Zulfiqar said.
Hiyaa little similar situation was handed to me yesterday for a Daewoo (GM) Nubira starter - same bosch reduction drive like ours, key it to start - whirrrr, no engagement.Took it apart - pinion slides freely n all, tested the starter on battery.the plastic fork that shoves the pinion had its foot pieces shattered, replaced that all was good.Maybe that'll help -