Monitoring the fuel system would be a good start as the lack of control would likely mean a defective OVP relay or its fuse. Really simple cheap stuff. Just do it. I'd start with EHA current on starting. Of course no key on engine off EHA current would be all one would need to switch the search to the OVP.

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