Hi -- got a 1991 740. Can't pass emissions due to high hydrocarbons. I found a broken vacuum line, so I'm going to replace that regardless, but in the meantime I'm looking at the EVAP canister. I can see vacuum lines connecting to the top of it, but while poking around there's a large rubber hose coming off the bottom that is open ended. I'm just looking for -- if anyone has it -- a breakdown of the "hookup" for this EVAP canister. Is that open-ended (large) rubber hose on the bottom some kind of "drain"? Surely not? What does it/what is it supposed to "connect" to? Thanks in advance.

 

It is a drain.

 

the evap canister should have zero impact on tailpipe emissions, its all about vapor capture and recovery from the gas tank. around here, it will be visually inspected, and a vacuum tester will be attached to the gas filler pipe, where they pump down the tank, then ensure it holds a mild vacuum for 5 minutes or something.

high HC typically means your engine is running too rich ... some things to check...

• vacuum leaks downstream from the MAF
• tired ignition system components (replace cap, rotor, protector disc, wires, plugs)
• worn out OX sensor
• worn out catalytic converter