Dad's ST/12

I'm working on my Dad's st/12 think it around 1975 model. i can check if i need to.  But just finished cleaning the carburetor (first one, besides chainsaw!) anyway got it started, but there is another small black plastic "box" that connects to the carb. Looks like fuel line goes to the box then to carb and to the lower part of the engine.   The tractor was worked on several years ago by someone else. They may have added this i don't know. but when the tractor is running, right now just idling in the garage. Oil is coming out of it.  can someone tell me what this is and what it's for...and if this is an issue how to fix. i did pull it a part an clean it. so at least it's clean.

image link below

black box off carb

THE BLACK BOX ATTATCHED TO THE CARBURETOR IS A CRANKCASE PRESSURE ACTIVATED FUEL PUMP. IT IS NORMAL FOR OIL TO BE IN THE HOSE TO THE CRANKCASE BUT IF YOU HAVE OIL LEAK AT FUEL PUMP EITHER A GASKET OR DIAPHRAM IS FAILED IN PUMP. EITHER GET ANOTHER PUMP OR YOU CAN RUN WITHOUT PUMP IF THE FUEL TANK IS HIGH ABOVE & BEHIND ENGINE, CAP OFF LINE TO CRANKCASE TO PREVENT OIL LEAK, ALSO CAN BE REPLACED WITH ANY BRAND OR KIND OF PULSE OPERATED FUEL PUMP. BOUGHT SOME FOR $10 ON EBAY.
GOOD LUCK
JIMMY

Thanks...guess I'll pull it off and double check it to. I took it apart and cleaned it. The gaskets and diaphragm seemed fine, I may have not put it back together correctly. I'll see if I can figure it out. Thanks again