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Fuel Tank Venting and the Charcoal canister

September 24th, 2010 · No Comments

Ever notice that when you fill up the tank of your GT that it starts to smell of gas? Also notice its not just temporary, it can last for a good long time up to say a ¼ tank of gas or more. Have you looked everywhere and have not been able to find the source? Have you ever wondered where those hoses to the canister are supposed to go and why? Well let me fill you in on how to do this and where the hoses all go. Seems that Opel wanted to keep it a secret and never really gave any of us a good guide line on any of it. I personally ran into this problem just recently and Opel GT Source sent me a fax immediately, of an old tech tip from Rodney Davis of the North American Opel GT Club (now a chapter of OMC). Rodney is unfortunately no longer with us, but his tech tips and advice are.
The Opel GT has an intricate fuel venting system built into the rear of the car and is mounted above the gas tank in the back under and behind the spare tire platform. What happens is this, the plastic tubing that makes up this system becomes brittle with age and starts to break apart and fall into clumps of hoses on top of the tank.
The venting system for the fuel tank consists of inlet tubes at diagonal corners at the top of the tank. These tubes are in turn connected to the fill pipe of the gas tank via a 2 – 3way tees and the plastic tubing aforementioned earlier in this article. The venting system is there to allow air into the tank to avoid a vacuum as the car uses its gas supply and also to vent the tank when heat expands the gas vapors in the tank as well. The clear plastic used by Opel for this system is obviously not designed to deal with the high temperatures of the car or the long-term exposure to gasoline fumes.
The fix for this is quite simple though. Use standard reinforced 3/8 or 5/16 gas fuel line, 5/16 works better, but 3/8 is easier to get sometimes. In addition replace the two fittings with 2 – 5/16″ tees available at any parts store. Also make sure to get the small hose clamps to clamp off each connection. This way you will never have to fool with this again. One note though, you will need to drill the hole that the vapor return lines goes trough the body at, just a hair bigger, since the fuel line is larger than the original material.
DO NOT try to cap that line off. You will develop a vacuum in the tank and it will cause the car to stall. You will have to use a coat hanger to feed the fuel line through the body and up from under the tank. I found it easiest to do this with the rear tail light lenses out, it helped me when I was trying to fish the line up.


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