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Fuel system

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  • Fuel system

    On my 1972 car there is a valve which I assume is a non return (check) valve. It is after the vapour canister separator and in the small pipe that goes through the floor and up to the front of the car. It appears to have a part number 820938 or 103686 for the USA version. Am I correct about its function? And how would I test it?
    I have a fuel vapour smell and I am replacing all the hoses but I am not sure about this valve

  • #2
    I am not familiar with the US fuel system, bit I have had problems with fuel hose.
    I fitted fuel injection to my GT 40, and after leaving it over the winter, the cabin reeked of fuel.
    There were no leaks, and I found out the hard way that modern fuels leach through Buna rubber.
    Changing to PTFE Aeroquip removed the problem.
    So be very careful which replacement hose you use, check the spec very carefully.


    • #3
      3-way diverter valve can get clogged with gummy deposits. Remove and clean without any pressure. You don’t want to dislodge the red rubber diaphragm. That’s why I had to split the one pictured. Diagram is from the shop manual. I also cleaned the vapor separator. One of my problems was the valve wasn’t removing excessive vacuum in the tank. I tried a number of things including replacing it ($135) and finally replaced the gas cap with a later vented one. I didn’t touch the charcoal filter. Make sure you check the condition of the large tank lines. They're pretty old, I had one leak and flood the garage.


      • #4
        I want to add that I think the tiny diaphragm opens to relieve tank vacuum and seals to prevent fumes from exiting. The valve spring is pretty strong it you wanted to test its functioning. I also had the gas odors coming from the trunk.