Joe,
Thanks so much for your reply. Please take a look at the attached image. I have indicated location of the guide and cap screw. I have removed the cap screw and inserted a screw driver, but could not locate the adjusting screw. I removed the upper solenoid to get a look at the internals and could not find an adjusting mechanism, only a spring loaded, hinged lever, the lower portion of which faces the guide hole. I could not see any adjusting mechanism or parts to which an adjusting screw could have been mounted. In other words it looks like it was intended to be the way that it is. Is it possible that some pumps were built this way?
Again Joe, thanks for your help.
Bob