as you go higher the vapor pressure decreases....
Here lets do a experiment.... remember in physics when you put a vacuum on a beaker of water in a vacuum chamber... it started to boil when the pressure decreased.... same with the fuel... it starts to boil when the pressure from way up their starts to be lower ... it starts to boil...
but,.....
you have another factor that comes into play with fuels... because they are airomatic they have lighter mixtures of stuff.... and so the temp, pressure and mixing all play a factor... if for instance the temp is lower... like density altitude the pressure is greater and also the fact that the temp is lower causes the voc (viscosity) of the fuel to increase... thus the vapor pressure is going to be much higher... in this case higher means lower pressure....
Now where can we get heat from... well the hoses can transmitt the radient heat... but, more the mechanical action of the pump while in operation can add to the heat of the fuel... and thus the vapor pressure would be lowere from say 14 to 10.... hope this helps.. G.M.
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