Re: Vapor lock

Posted by DavidM On 2009/7/2 7:50:10

My experience with vapor lock is confined to the Packards of the 1920's where it is a serious problem here in Australia in hot weather and long climbs. I have been told by a fuel company engineer that the problem in our old cars will be much worse today than many years ago. The reason is that modern fuels have a lower boiling point to suit the modern high pressure fuel injection systems. The high pressure raises the boiling point well above the engine bay operating temperatures so that it should not be a problem in fuel injected cars.
I live with this problem by adding up to 10% kerosene to the fuel in summer, as recommended by the fuel company, I have tried diesel but it was not very effective. An electric fuel pump bypassing the vacuum tank (pre-fuel pump) would be a better solution.
My 1922 Packard has the original "Packard Fuelizer" carburetor which incorporates a small combustion chamber to heat the fuel, presumably to aid vaporization in cold weather. A small amount of fuel is bled into the combustion chamber on the carburetor where it is ignited by a glow plug operating from a separate coil. The mixture is adjustable and the hand book describes the procedure and correct flame temperature. Obviously this is not used today.