"Vapor Lock", what is it, really? Options

[Trekkor]

On a hot day my 2.0 doesn't start well after normal temps or hard driving.
Most people would say," that's vapor lock ". OK . What is that?
What's actually happening?
How do I make it go away forever?

please instruct.

trekkor (IMG:style_emoticons/default/confused24.gif)

[airsix]

The boiling point of a liquid is a function of temperature and pressure. The lower the pressure the lower the temperature required to boil. If you draw gasoline through a long fuel line with a pump, the fuel in the line will experience a drop in pressure, and therefore a drop in boiling temperature. If it's hot, the drop in pressure may be enough to reach boiling point. When the fuel begins to vaporize in the line it can no longer be pumped. The only way to stop this is to lower the temperature or increase the pressure. Most modern cars have the fuel pump in the tank or very near the fuel tank. The reason for this is to pressurize the fuel in the long lines between the tank and the engine. Placing the fuel under higher pressure like this eliminates the possibility of vapor-lock because it raises the boiling point to a much higher temperature.

Just as an FYI, some grades/blends of gasoline will boil at temperatures as low as 100F. If you lower the pressure, the boiling temp is even lower than that. The two biggest factors regarding pressure, are:
1) how far is the fuel being drawn with the pump (you want the pump to push the fuel, not draw it)
2) atmospheric pressure (ie. a car might be fine at sea-level, but has vapor-lock problems at high altitudes)

-Ben M.