Agree. I had a problem with the shutoff valve (300SD)and had to replace it. However it was tricky getting the red lever to cut off the engine beforehand. I would guess that it was just not tight enough; took several attempts each time with the lever over a period of a couple of months before I finally replaced the shutoff valve on my 1981 300SD.

Have not had to use the lever since. Not sure about a 240D but you might have a bad shutoff valve at the back of the injection pump.