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Discussion Starter #1
After some spirited driving, fuel weeped from the end of the hose zip tied to the solenoid vent line. At first I figured this had to have broken or disconnected, but I'm not finding any reference to it or connection nearby.

Where is this line supposed to connect? I also heard what sounded like bubbling fuel, like it was boiling, inside the plenum. Surely that can't be normal.

Thanks in advance.

Cab
 

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Discussion Starter #3
These shots are looking down onto the top of the passenger side inner fender at the space between the intake plenum and fender. Where that's supposed to connect is the mystery. The line does not appear to have been severed and it's not brittle.
 

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These shots are looking down onto the top of the passenger side inner fender at the space between the intake plenum and fender. Where that's supposed to connect is the mystery. The line does not appear to have been severed and it's not brittle.
Where does the other end run to?
I wonder if the charcoal canister filter? If the S4 has it.
 

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But Mad North-Northwest
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Pretty sure that's the vent line to the charcoal canister. It's an open tube that comes out from the fender area. The early S4 cars just left the top port of the canister open, but on the later ones they added a hose that goes up into the engine bay.

If you're getting fuel in there you must have fuel in your carbon canister, which...hell, I don't know how that happens. Overfilled the tank maybe, which flooded the separator in the trunk?

If the canister is full of fuel, that could cause liquid fuel to be dumped into the plenum when the purge valve opens, which might explain the bubbling noise.

I would start by inspecting and disassembling the tank vent system in the trunk: it may all be full of fuel. You should also verify that the purge solenoid is working - pull the wires and apply 12V to the solenoid and make sure it opens.

Beyond that, if the canister is really full of fuel you may need to pull it out from the secret compartment behind the front wheel and drain it.

Do a search and you'll find more details on these items.
 

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Discussion Starter #7
Thanks Tom! Yes, the line comes out from the fender, so that's got to be from the canister. With your info, I found a 2013 thread where someone experienced the same fuel boiling sound I heard. I suppose the canister could fill up with fuel if the solenoid has failed or not operating correctly.

If it matters, I was driving on track, pushing harder than normal street driving. When I stopped, after I shut the engine down, the buzzing noise I sometimes hear from the front of the trunk was quite a bit louder.

I appreciate the help and education.

Cab

05-23-2013, 03:22 AM
BobHalfa
Registered User

My S4 was made in Jan. of '91 and there is that hose marked with the blue arrow from the charcoal canister to the solenoid valve. The solenoid valve opens up at about 1500 rpm to evacuate the charcoal canister and is closed at idle. The connectors on the solenoid came loose on mine and it created pressure in the gas tank that made the gas sound as if it was boiling after the car was shut off. If the output side of that solenoid is blocked off with a screw it could cause problems.
 

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Tom has it right. That hose vents from the charcoal canister on later S4 spiders.....earlier S4 spiders (mine is may 1990 euro S4 and does not have that hose, for instance) actually vented inside the fender (where the charcoal canister sits).........I think Alfa changed the design to prevent fuel smells finding their way from inside the fender to the interior cabin.

Luckily the S4 canister is plastic, unlike the earlier metal ones which tended to rust out over the years.
(photo from BB)
 

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