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Thread: fuel vapor line, where does it end?

  1. #1

    fuel vapor line, where does it end?

    While underneath my '70 S, I noticed the fuel vapor line exiting the tunnel was disconnected. Actually, it looks like someone cut it 3 inches past the tunnel.
    Where does the line connect to? Is it really needed, can I plug it?

  2. #2


    The two lines come out of the tunnel and connect, one the top of the fan shroud for positive pressure and the other hooks up to the air filter box which creates a suction and evacuates the charcoal canister. So as you can see the canister collects vapor and once the engine is started the canister is pressurized from one end and is sucked on from the other moving the vapors into the airbox to be burned. The canister system is for US model cars only and does cut down on gas smell if the car is sitting around. If the car has it I recommend that it either be hooked up and working in its entirety or that it is set up like the rest of world cars, and all of the many holes and hoses for the system are addressed.

  3. #3

    fuel vapor line

    Thanks for the help. SEVERAL mechanics I have spoken to have all said "don't worry about it" and suggested leaving it alone. This means tubes exiting tunnel exposed, and no connections to shroud or air filter box.
    Questions: which hose is connected to the shroud,which to the air filter box. Does it matter? How do I eliminate the whole cannister, vapor lines? Is it a good idea to do that?
    Thanks again

  4. #4


    There may be a inlet and an outlet side to the canister, the inlet side should be the same side as the one with the small tube running into it from the expansion tank under the left front fender. This end thus should be hooked up to the pressure side at the air shroud.

  5. #5

    fuel vapor line

    Thanks for the help. Coincidence, This topic is going on now at the Pelican BB, "what is this." Most people are suggesting to remove canister and all lines attached, including the expansion chamber at the back of the drivers side fender? What do you think?

  6. #6

    bad gas

    The system works great if it is all entact and I would suggest preserving it. Porsche went to great lengths to add this system to the US and a few other markets like Japan. The tunnel has brass lines that begin at the right side of the foot well and end at the rear of the car on the left side of the tunnel where the fuel hard lines exit the tunnel. In addition the fuel neck, the inner fender behind and above the drivers side strut and above the drivers side battery have exit tubes that are brazed into the body of the car. One is for the filler neck and the other for the overflow tank behind the headlight. There are also hose line brackets under the car to support the soft lines as they exit the tunnel, as well as a large innner fender bracket to hold the overflow tank. On the
    European cars none of this stuff is on the car, all that exist is the three holes for the inner fender tubes that are plugged by plastic caps and one has a grommet and a hose exiting it. The system works great and keeps fuel smells out of the car and out of the garage. It is indeed noticable the difference of a fully sealed system. On the European cars there is only a line from the tank to the expansion box under the cowl and then it exits straight out using a length of tubing behind the outer portion of the battery box using one of the holes that the US model car would have a tube brazed in and connected to the overflow canister.

  7. #7

    vapor lines

    Thanks for the help. I will keep it!!

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