Tests are what I'm asking about, but my usual approach is to throw parts in the air. I'm not sure sure on the proper testing process. I sell parts for a living, so I usually have a bunch of stuff hanging around. Not so with this car.

I'm considering buying a 190e parts car and just doing a fuel system overhaul on this car. Oil has been blowing out of a disconnected hose on the valve cover vent for some years now. So I really want to disassemble the system, clean it and reassemble the whole thing. I am unsure at this time whether or not actual parts are at fault, or if the oil soaked and heat baked wiring may be the cause.