thanks to everyone for the insights- It's been very helpful so far!

I've discovered that jumping the +12constant and fuel pump pins makes the pump run. cool!

I also put my meter on +12 and ground - good
+12 ignition on - good
+12 cranking - good

I did not check the connector inside the car, assuming all was well.

when I put the relay on- no start, it turns forever, but no fuel pump action at all. aaahh!

I decided to explore the inlet to the fuel distributor. there is plenty of fuel pressure. the inlet filter was not clogged.

I did notice that when I loosened the nut, I got a bit of gas spray as the system depressurized. is that normal, or a sign of a flummoxed fuel distributor?

I thought I'd try starting fluid. - I get nothing.

what could it be now?

thanks to everyone for your help and the pinout of the kickdown relay connector.

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1967 250SeC
1979 450sel 6.9 (usa)
2009 S550