There isn't a fuse involved. The pump can be jumped by crossing pin holes matching the circuit designations 30 and 87 on the relay. They should be next to one another at the center of the socket.

As to the relay you tried, what is the MB number on it. The FP relay looks about identical to the Klima relay for teh AC.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician