Oil Leak on 6.5

[tuckedawaytoo]

I recently bought a 1995 GMC 1 ton van to work with. My first diesel so please excuse the ignorance. It has developed an oil leak. The source is somthing I'm not familair with. It is leaking from a part that inserted into hwere a distributor would go on a gas engine. The part is held in with a "clip" similar to a gas engine. The leak is not from where it goes into the engine but from the part itself. It has a black plastis "cap" that is "banded" to a metal base. A two wire plug goes into the part. The oil leak is right from the top of the unit. Can anyone tell me :
1) WHAT IS THIS????
2) If replaced is positioning critical?
Thanks in advance
Anthony

[GOEHILL]

I Don't Know If Your Van Has A Vacume Pump On The Front Of The Engine, Belt Driven, Or If It Is In The Valley, Where The Dist. Would Go. If It Is A Small Unit It Is For The Computer To Read Engine Rpm. If It Sticks Up Further Then It Is A Vacume Pump. Either Way You Pull It Out Just Like A Dist. But When You Put It Back You Don't Have To Time It. Just Drop It Back In.

[tuckedawaytoo]

There are no vacuum lines to this unit ... just two wires. Guess it must be for engine rpm ... Thanks!