Rear pipe from air cleaner - what is it for?
 

I removed the air cleaner from the 1991 560SEL and closely examined the black rubber/plastic tube (approx 10" long) that connects to the left rear metal pipe coming from the air cleaner housing. I noticed that the black rubber/plastic tube has an extra "feeder" branch (small diameter) that doesn't appear to connect to ANYTHING. Does anyone have any ideas what this branch feeder hose is for?


http://s324.photobucket.com/user/cha...7cdc0.jpg.html

I believe that SHOULD have a hose that goes to the back of the fuel pressure regulator. In the event the FPR fails, fuel will leak out the diaphragm through a vacuum hose and into that breather hose so that it is burnt off rather then just dumped into the engine bay areas.

Exactly correct. There should be a rubber vac connector on the FOR for this line. It is routed between the underside of the CIS airflow/fuel distributor assembly on top of the intake manifold top casting.


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Where is the FPR located? Do I need to purchase a hose to run from this branch circuit to the FPR? If so, does anyone know the part number?

If you remove the air filter you'll see it .

Looks like this guy:
http://i787.photobucket.com/albums/yy159/petrusky70/Mercedes/IMG_5504copy.jpg

I think that pic is from a different car but the FPR look the same.

I'm not sure on the part number.

OK, thank you, it is easy enough to see from the photo.