Quote:
Originally Posted by 80stech
That's a good question, I have wondered that myself. The purge valve purges the charcoal canister so your problem might with a restriction or saturation there. I would imagine that the air inlet would be on the charcoal canister or a hose to it. There are some pretty good hose diagrams(it is fairly complicated) in the Bentley manual.
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I think the air solely has to come in from the filter on the DMTL input and not the gas cap. There really aren't that many hoses as part of the system. I found this diagram in some BMW training material, and it lays it out pretty well.
It also says 'The pump also contains an ECM controlled change over valve that is energized closed during a Leak Diagnosis test. The change over valve is open during all other periods of operation allowing the fuel system to “breath” through the inlet filter (similar to the full down stroke of the current vacuum operated LDP).' in the functional description.
I blew some low pressure air/smoke (<5psi) back through the hose that goes from the canister to the purge valve, and smoke did come out of the rear fenderwell where the DMTL pump is located, so I assume that path is clear. Maybe I'll hook up a vacuum pump and gauge and see what kind of vacuum I pull going the other way.