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Fuel Tank Components


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Hi - Can anyone help me identify the items circled in the attached photo?

Thanks in advance!

Derekpost-10062-013108800 1284120242_thumb.jp

I am just guessing now.... The smaller circle is the overflow and the bigger one with the electrical wire is the valve for the vapor recirculation system... Just found out the valve is called fuel tank vent valve. part# 996 605 203 01

I am really surprise that you have the complete tank out of the car. Can I ask why?

post-29683-098546900 1284127145_thumb.pn

Edited by jpflip
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Loren - thanks - you are right (it goes to the carbon canister) - do you know the purpose of the valve?

Jpflip - I am converting the car from Left Hand to Right Hand Drive - hence the need to change the fuel tank and the sheetmetal surrounding it. The RHD tank that I have has a slighlty different arrangement - there is no blue circle, just a connection point higher up on the tank. To incorporate the valve, I need to make up a special bracked and find some elbows to put in the line - I am just trying to determine how important it is / what it does....

Would anyone have a logic diagram for all the vents connected to the tank?



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I don't know of Australia cars have charcoal canisters and venting tests like the US and Canada.

Basically that vents gas fumes through the charcoal canister where it converts the vapor back into the engine to be burned or if the car is not running it returns them to the tank. It's for emissions and the environmental protection.

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Thanks - Australian emission requirements are very similar to California - the tank I have came from a wrecked car in the UK - also 2001 model - I am surprised that the connections are so different.

Loren do you know the logic behind the valve - ie under what conditions it is open and when it is closed?



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Tank Venting System

Fuel vapor is collected in the carbon canister. This canister is mounted in the front, right-hand wheel arch. The fuel vapor collected in the carbon canister is fed back into the combustion cycle. The carbon canister is purged with fresh air thus regenerating the carbon.


An electromagnetic valve is installed in the line between the intake housing and carbon canister. The flow direction of the one-way valve is imprinted on the plastic housmg. the valve is secured above ttie alternator attached to tne intake housing.

The tank venting valve is clocked under map control with warm engine and active oxygen regulation. The resulting pulse duty factor is dependent on the airflow rate of the engine and the load density of the carbon canister. When the mixture drifts from lambda = 1 towards a rich or lean setting (caused by the purging of the carbon canister), this is detected by the control unit via the oxygen sensing system and is corrected by readjusting the mixture control during the tank venting phase. The first purging phase is performed after the engine is started and when the appropriate operating conditions are reached (engine temperature and oxygen regulation operations). It is ended by the DME control unit 250 seconds after the engine has been started. The mixture adaptation phase is then performed for 100 seconds. The next tank venting phase occurs, and so on.

Operation of tank venting valve

The tank venting valve is constructed in such a way that it is closed when the ignition is off. If the ignition is switched on, the DME control unit applies a positive potential to the tank venting valve via terminal 54. When the engine is started and the operating conditions described previously are reached, the tank venting valve is once again connected to ground by the DME control unit, but via terminal 61, and opens. When the engine is switched off but the ignition switch on, the Porsche System Tester 2 can be used to check that the valve is functioning correctly.

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