Hi,
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Originally Posted by SoopahMan
That's really interesting. So are you saying the vaporized gas is actually diverted and burned separately to power separate systems not driven by the rest of the vehicle's power system/drivetrain? And the volume of vaporized gas surrounding the bladder actually dictates the pressure pushing on the bladder?
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From what I can tell, that seems to be part and partial of how the system works. Unfortunately the maintenance manuals tell us "what" not "how."
Traditional vehicle tanks have a hose that goes to a carbon canister. As the tank fills up, the carbon canister absorbs the fumes and later, they are purged when low pressure in the intake manifold opens a 'fresh air' valve. A modification of that system still exists in the Prius but the valves appear to be computer controlled.
The maintenance manual has a schematic of the fuel system pipes and valves but lacks the 'principles of operation' that would clarify what is going on. My thinking is a low-pressure gage, 0-10 psi, should let us find out if the pressure between the bladder and tank increases during fill-up . . . sometimes.
Working on the hypothsis that engine operation might 'normalize' the pressure, I tried topping off the tank, driving 5 miles and topping it off again. I treated these two as one ''tank." But the same variability remained.
The next test, when I get around to it, will use a pressure gage on one of the hoses to the space between the bladder and tank. This will hopefully tell us if vapor pressure here has anything to do with it.
Bob Wilson