Thanks, Richard. Actually, I did replace the pump recently. Around Christmas time. I bought it from another Mercedes parts dealer. It was the "Monark Diesel" brand one. I had to remove the elbow adaptor from the side of the block in order to fit it on.
As I mentioned, I have a spare Stromberg for parts, so I'll take it apart and see if maybe there is a problem with mine and pull a swtich.
I really appreciate your expertise!
1976 230.4 W115