Engine Mechanical problem
1981 Datsun 710 4 cyl Two Wheel Drive Manual 200000 miles

i have a nissan pickup diesel the sd22 engine when i start it up it runs like a champ / but when i go and turn it off at the key it keeps running ?? what i have seen and need to do is rais the hood / and on the passenger side of the engine thair is a leaver and rod loos / if i move the rod by hand the engine will stop / how do i fix it can't find a repair book for it and not sure of all the names of parts if a picture well help please let me know and i well take and up load one