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  1. #1
    Join Date
    Mar 2011
    Location
    Taree NSW
    Posts
    86

    Default Fuel smell in car

    I have a fuel smell within my car which I have been unable to stop - all hoses have been renewed with unleaded compatible rubber, the tank has been pressure tested and there are no visible leaks - when I last checked the sender unit the 'O' ring had grown in length so I replaced it with another - maybe that 'O' ring is also incompatible with petrol so I will check its composition - the tank doesn't appear to be vented - any ideas? The car is a 1969 NSU Ro80

  2. #2
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    299

    Default

    Is the smell present before starting the car? There are a myriad of things to check as you are obviously aware of, maybe a wrong float setting, leaking needle & seat might be culprits and it does not take much for the smell to be noticeable. Try searching with a lit match........I'll leave before you do. One thing you might do and only very carefully is to use a few PSI of compressed air to pressurise the whole system but the vents will need blocking off as cars this old did not have sealed fuel systems and the whole system between the pump and the carburrettor only operated at 2 to 3 psi and anything more overcomes the ability of the needle & seat to seal. Have you checked the float to make sure it does not have a leak as well? So many possibilities and not much fun trying to find the reason makes a job like this very hard.
    CHRIS

  3. #3
    Join Date
    Dec 2005
    Location
    South Australia
    Posts
    850

    Default

    Carburetor cars pretty much always have some lingering fuel smell, in older vehicles it will enter the car through a 101 places worn wind lacing, worn window seals, worn grommets at body perforations
    etc. etc.

  4. #4
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    299

    Default

    Quote Originally Posted by China View Post
    Carburetor cars pretty much always have some lingering fuel smell, in older vehicles it will enter the car through a 101 places worn wind lacing, worn window seals, worn grommets at body perforations
    etc. etc.
    Not in my experience at all if the system works the way it was designed and has no faults. They are certainly more susceptible to more faults as modern methods have ensured leaks etc are just about a non event. On old cars the system vent on the tank can be a problem if it is damaged or moved.
    CHRIS

  5. #5
    Join Date
    Dec 2005
    Location
    South Australia
    Posts
    850

    Default

    Ok Fair enough, the car is 50 years old, what I was trying to say is that there are many many many places that fuel or fuel vapours can escape for instance Carburetors are made from zinc type materials and move and
    distort over the years, I suppose what I should have said is it can become very time consuming to find and most people end up just living with it

  6. #6
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    299

    Default

    If I couldn't find the leak I would rip the whole lot out and replace everything between the tank and the carby. That would leave just the carby and the tank as the culprits. gee I am glad I gave up working on cars especially old ones, all my tools literally have rust on them due to being no longer used. I often wonder why I even keep them apart from a few metric spanners.
    CHRIS

  7. #7
    Join Date
    Dec 2010
    Location
    Syd
    Posts
    409

    Default

    Assuming it's stockish and has a mechanical fuel pump, I'd check if there's residue evident around that. Often found stinky carb cars had a perforated diaphragm - they'd still run fine.

  8. #8
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    299

    Default

    Quote Originally Posted by Hunch View Post
    Assuming it's stockish and has a mechanical fuel pump, I'd check if there's residue evident around that. Often found stinky carb cars had a perforated diaphragm - they'd still run fine.
    I doubt that is an option to pursue as being a rotary it has no camshaft.
    CHRIS

  9. #9
    Join Date
    Mar 2011
    Location
    Taree NSW
    Posts
    86

    Default fuel smell in car

    Quote Originally Posted by Chris Parks View Post
    I doubt that is an option to pursue as being a rotary it has no camshaft.
    Tank is in boot and fuel pump is behind rear seat = there are no visible leaks - 2 mates from local car club brainstormed the problem yesterday and the theory currently is that the tank vents out of the fuel cap which is in a pod on the car side, this pod has a drain to ground which takes care of splashed fuel if one overfills tank - if that drain is split it could allow fuel fumes into car - will check for split and block drain temporarily, also when I had tank pressure tested I found the 'O' ring under the sender unit had grown due to incompatibility with petrol - will replace this 'O' ring with suitable composition material if available - SO, 2 possibilities, will report back when they are eliminated

  10. #10
    Join Date
    Dec 2010
    Location
    Syd
    Posts
    409

    Default

    Forgot about this being the devil's device!

    Might find too, even if the rubber hose is good for unleaded, it doesn't necessarily mean it won't smell. There's an E85 car here with alcohol safe hose, still stinks where it's enclosed.

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