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?

Attached Thumbnails

 

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.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

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.


Sent from my iPad using Tapatalk HD

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.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

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