Unplugging the connector to the pump disables the clutch and is for testing.
If you are going to drive it a while with the clutch disconnected, you also should disconnect and plug the vac line to the air valve between the pump and the head. This valve is energized by a switch-0ver valve in the same circuit as the pump clutch and has to be disabled if the pump is not to run.
Otherwise , the feed hose to pump will be opening even though the pump is not on...
No good.