Breather canister from fuel tank + MAF problems?

[Nosmonkey 10]

Hey guys, i have a late spec (1996) VR6, ran VAG-COM on it and i got fault codes 00735 and 00553. the first code relates to the recirculation system which i believe is supposed to relieve the fuel tank pressure/vapours into the engine via a carbon canister. I have found the fuel line and a connector which i believe is running from the ECU which is not connected to anything just below the MAF housing. The line is venting the vapours into the engine bay so i can only deduce that the canister is missing?

Would anyone be able to advise me where to purchase this part from?

 

With regard to 00553 fault code, this is a problem with the MAF itself i believe. I found a guide on testing the MAF, on one of the pins i should be getting a reading of around 12V with the ignition turned on, however i was not getting any reading from this, which leads me to believe that the wiring from the ECU to the MAF is past it! How would i be able to check if the problem is with the ECU or the wire? Is there anyone out there who would be able to identify which pin/slot that wire plugs into on the ECU?

 

Sorry for all the noob questions, your help is much appreicated!

 

Cheers

 

Nos :afro:

[Critical_Mass 10]

Inregards to the carbon canistor and the fuel tank vent. People do remove the canister, leave on pipe venting to atmosphere and the other should be blocked up. If you look under the airbox the canister sits under it. If its been removed there will just be a hole where it used to sit. You dont NEED this part, as the carbon in it is probably well spent by now. The problem i found when i removed mine (now reconnected) is i could smell the petrol fumes in the cabin. Even though i put the cable in down the hole the canister sat, so it vented behind the bumper and the fumes would go under the car.

[Nosmonkey 10]

ah right i see, the thing is i get the occasional puff of smoke from the front rhs of the car aswell, which i hope is not the fuel vapour smoking.....

[Critical_Mass 10]

RHS as in drivers? hmmm cant see the vapour smoking though.

[Nosmonkey 10]

yeah drivers side, only puffs very occasionally though.

[Critical_Mass 10]

Not oil dripping onto the manifold or something, Smoke suggests fire and i think you'd know if the vapours were alight.

[Nosmonkey 10]

Just went for its MOT, CO level was hitting 8%, so ECU will be out this weekend and do some continuity checks on the wiring to see what the problem is.

[Stonejag 10]

As already stated the carbon canister fits into a circular hole under the airbox (or where the airbox would be if you have a BCM CDA / cone filter instead). From memory the vent line from the tank goes directly into the canister. The second line on the top of the canister goes to the carbon canister valve - a small, usually blue cylinder with a hose barb on each end and a 2-pin harness connector in the middle. Never chased the wiring myself, but the end furthest from the carbon canister is attached to a vacuum line from the top of the head (near the left side of the throttle body). If the canister's been removed this port should be blocked or you'll get a very rough idle. If the connector you've found is the one I think it is, the error is probably the ECU realising the valve's not there - I read somewhere else that it can detect open and short circuits. In a Mk3 removing the valve lights your Check Engine light but we never got one of those ;)

 

Here's a pic of a spare valve I had in the bits box (this is a Golf VR6 one but it looked the same at the autojumble :) Pretty sure they're the same though. Part number 051 133 459A)

 

Although the canisters will all be long since spent they do stop the petrol vapours from the tank vent escaping into the engine bay and getting sucked up by the fans, as you and others will have found! Some people vent them into the air intake via the valve which is probably the least worst thing for you to do - leaving it open lets moisture into the tank and lets petrol vapour out, whereas running it direct to the inlet puts manifold vacuum on the the whole tank which is probably bad.

 

FYI, this pic shows the valve as part 12; it's part number 034 133 517 "solenoid valve". I can't find the canister at the moment but that should give you something to go on!

 

Best,

 

Stone

Edited November 20, 2012 by Stonejag

[Nosmonkey 10]

Thanks stone, very informative post :)

Sorry to ask another question, but do you know what part 5 in the diagram is? Some kind of breather?

[Stonejag 10]

That's the throttle damper, it plugs into the idle control valve (part #1) and stops the throttle snapping shut instantly when you take your foot off the gas. The little nubbin that connects to pipe #4 is solid - it doesn't connect in, it's just to support it mechanically. Pipe #4 is joined to the outer edge of the inlet elbow (the plastic or rubber bit in the top-left of the engine bay that connects the airbox to the throttle body), and once the idle control valve and damper have done their thing pipe #3 connects the air feed into the throttle body to allow it more or less air depending on how the idle's doing :)

 

It's a pretty overengineered system and doesn't work very well, which is why the VR6 idle is so lumpy! They ditched it on the later OBD2 engines fitted to the Golf VR6es and did it all electronically :)

 

Stone

[Nosmonkey 10]

Thanks a lot mate, very helpful!

Here, have some rep :geek:

[Nosmonkey 10]

Does this seem normal?