[DeTomaso] vent line weirdness

[JDeRyke at aol.com]

Chris, the way a gas tank vent-line anti-rollover valve works is, there's a 
small ball inside. If the car becomes confused as to which side should be up 
and inverts itself(!), the ball, acting via gravity, moves to the other side of 
the valve housing and blocks the exit. In this way, you don't empty your gas 
tank while you're upside down; hot engine parts could make things toasty with 
the driver still inside. 

Since all cars sold world-wide since about 1980 have this device by 
imnternational law, its possible you got a defective valve, but I've not heard of such- 
on any make.   What apparently happened was, the ball somehow got stuck- 
either in the 'up' or the 'down' position and perhaps before you even installed 
it. It has nothing to do with how you hooked up the valve, or where the hose 
went. For instance, an engine sucks equally from all points inside a non-sealed 
air cleaner so the effect of intake suction on a hose in an air cleaner would 
be the ratio of 5/16" OD vs 14"OD x 3" high in square inches, or 
almost-zero-pressure. 

I'd remove the valve and shake it; a rattling, clicking sound from the 
semi-loose ball should be heard; if so, maybe the valve body is somehow getting 
distorted when its screwed down. If no sound, perhaps some sticky stuff got 
splashed up inside. Replace the valve or clean it out with solvent (the body is 
nylon so don't soak it for weeks.... dunno what material the ball is) and 
reinstall. Watch the torque on those screws; they need not be super-tight (just in 
case the top of your tank is not quite flat). You can also check an installed 
valve with your bicycle pump or a quick squirt from an air compressor, with the 
std non-vented gas filler tank cap off. Air should flow into the tank thru the 
valve spud with the gas cap off. Good luck- J Deryke


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