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Charcoal canister supposed to suck in air?

fungist

Passed Driver's Ed
Location
norway
Hi.

Im playing around with a evap code "incorrect flow" paired with a lean at idle.

The nipple right under the cap/head of charcoal canister sucks tons of air in.
Having high idle 1.1k, rough and stutter.

My trims are: stft 5% ltft 9%

I figured that when i block the nipple my idle gets back to normal and im watching the
Stft drops fast back to 0.1%.


So i blocked it with a homemade cap and running with this nipple blocked gives me
Fine idle and great trims. However i seem to trigger the same evap code just faster.

Also blocking this nipple seem to "shrink" the canister. I can see the walls of it getting
Slightly sucked in.

I guess the nipple are there for a reason? But it sucks lots and lots of unmetered air into
My manifold!

Any inputs on this?
 

fungist

Passed Driver's Ed
Location
norway
I found on google that n80 is supposed to be closed at idle?
Is this true? Cause its sucking from tank into engine. Its a pretty strong vacuum
 

3carmonte

Gelbrain
Location
Seminole, FL
Car(s)
2007 GTI DSG Coup
Engine vacuum is highest during idle in the intake manifold. The vapor recovery is closed at that time. The solenoid valve only opens after manifold vacuum drops (higher rpm's). The flow sensor must be seeing that the "n80" is open all the time and telling the ecu about it. Why is the canister vapor locked?

"So i blocked it with a homemade cap and running with this nipple blocked gives me
Fine idle and great trims. However i seem to trigger the same evap code just faster.

Also blocking this nipple seem to "shrink" the canister. I can see the walls of it getting
Slightly sucked in
."

There is a (filtered) vent into the gas tank so that when vapor is vacuumed out, pressure can equalize. Do you hear air rushing into your fuel tank when you open your gas cap? I'm not sure what your blocking...
My experience with this system is not on our cars but a Ranger P.U. truck. The canister charcoal was breaking up and getting sucked into the flow valve jamming it open. I replaced: canister, flow valve, flow sensor and all associated hoses as a set. Problem solved. Good luck!
 
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fungist

Passed Driver's Ed
Location
norway
The for the info.

I studied in vagcom the n80. It was 33% open at idle. I ran a basic setting 70 that failed at 66%
Saying evap not ok.

I throttle a bit seeing n80 goes back to zero and i let it idle again, now it rises to around 33% again before it settle.

Im not sure if this is good behaviour or not.



I decided to replace the n80 with a old valve i have lying around thats already worn.
However this valve lets me pass the test but it still act the same way as the old valve.
40% open at idle.


Maybe both are just shot..



I dont have a "ssshhhhh" when opening gas cap. I might get it sometimes.


Theline that goes from the canister to the fueltank is not possible to blow or suck through. I dont know if there is a valve on the fueltank side or if its possibly blocked? Cause as soon as the n80 opens, that vent/nipple underside the canister which arent connected to anything, starting to suck in air.



You can see that nipple im talking about right below.
I have no idea if its supposed to went to air or be connected to anything


 
Last edited:

vwengineer

Ready to race!
Location
Switzerland
The N80 is not supposed to open when the engine is cold, it should begin to work when the car is warm. You can test it by trying to blow through the valve directly. You should not be able to blow through at all.
 

3carmonte

Gelbrain
Location
Seminole, FL
Car(s)
2007 GTI DSG Coup
RE: "Theline that goes from the canister to the fueltank is not possible to blow or suck through. I dont know if there is a valve on the fueltank side or if its possibly blocked? Cause as soon as the n80 opens, that vent/nipple underside the canister which arent connected to anything, starting to suck in air."

I'm thinking this has to be the "vapor pipe" from the tank to the canister. Then through the canister (to filter the evaporated fuel) thru the flow valve ("n80"), thru the flow sensor, to the vacuum port on the intake manifold. The vent for "make-up air" to the tank I believe is located in the rear of the car behind the interior cover on the right side. I remember a forum member mentioning that the filter to it is replaceable. I could be wrong about that memory though but there has to be a check valve vent somewhere. (Check valve is air in but not out. We don't want any vapors coming out into the cabin right?) The gas cap closes the system. How the ecu manages all of this in our GTI's is unknown to me however.
The vacuum is reaching the canister but the canister can't pull vapor from the tank through that line for whatever reason...
 

fungist

Passed Driver's Ed
Location
norway
I migh have a look at the lines and the ldp.

The ldp evap test (leak detection pump) is blank in vagcom, not possible to run.
Also my gas tank is not pressurized lately. Could i be having trouble with the ldp? I think there is a 1way valve on the ldp is that correct? I was thinking it could be stuck or something.

Im going to look at lines and make sure they arent blocked.

Would be intresting smoketesting the gas tank.
Maybe a bad fuelcap seal too.
 
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