Missing Woodruff key W108 250SE pump

[Tassie Tiger]

Hi,
I have recently refurbished the carbon brushes on my 250SE fuel pump. It is the tall type of pump. In the process of dismantling the pump, I've lost the Woodruff key that stops the impellor from spinning on the shaft.
The specifications state the key is 2x1.5x1.5mm. I have tried making one from key steel but it seems too small and falls out.
I would appreciate if someone could offer advice on why this is not working or where I could purchase the correct key.

Thanks
Alex

[97 SL320]

I'd say to make another one. From the Bosch VW FI pumps I've taken apart, the key should not fit tightly. A slightly loose key will allow the pump element to float rather than bind. The ends of the key need to be slightly rounded so they don't scrape the pump housing.

[Tassie Tiger]

Thanks for your response. Would you have the dimensions for the key? I measured the notch in the impellor and the ground flat section on the impellor shaft and get a dimension that would accept a key of 4mm x 2.5mm x 2.5mm. Does this sound about right to you?

Thanks

[97 SL320]

Sorry, I don't have any dims. I'd use whatever dims made for a slip fit between the shaft and rotor.

The last time I took a Bosch pump apart was in 1980 or so on a 1969 VW type 3 Square back wagon.

There is a recent thread here where someone was fixing a leaking fuel pump but I don't think they measured it.