To start answering my own question. I found a pump from my long gone 1994 E250d. It threw me off for a little while because it had a 6-way vacuum connector fitted.

But the connector came off easy enough and then the pump was a direct swap for my 1989 230ce. Who would have thought! And voila- all locks lock all locks again!

Having a working pump in the car allows me to play around with the old one. The lid comes off easy too, and reveals a small circuit board with just a handful of components. No fuse.

I almost can’t believe this is not working on one of the circuits. Don't have a meter here. Will report back later!