"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)

[lapuwali]

More or less it's the gas boiling in the lines. Fuel pumps rely on the fact that liquids are basically incompressible, so they only have to give it a little shove and the fuel will keep moving. However, if there's a big pocket of highly compressible vapor in the lines, the fuel won't go anywhere. The boiling causes that vapor. This will happen more often at higher altitudes, where the boiling point of the fuel is lower.

To make it go away, you have to remove the sources of heat in the lines, like moving the fuel pump out of the engine bay to under the tank, like the factory did. Marginal fuel pressure (like a dying pump) will also make this worse. Higher pressure raises the boiling point.

A hot start problem can be caused by other things than vapor lock. The CHT sensor (Temp Sensor II) may be bad, or your cold start system is operating in higher temps than it should.