Did you buy those 3-way rubber vacuum connectors from MB or from K-Mart?
I ask because it sounds like they may be the wrong size. They should not leak.
Also, just for comparison, a properly running shutoff valve system should shut down a diesel so fast you'd think you'd cut the ignition on a gasser. Almost the instant you turn the key.
Now if you have something sticky INSIDE the injection pump, well.....
Ken300D