Fuel Filler Caps

[Tom Cloud]

>A small point, I think it's actually a vacuum.  The charcoal 
>cannister and engine vacuum are used to maintain a slight negative 
>pressure in the tank in order to reduce evaporative emissions.  
>Supposedly a defective cannister system can collapse a gas tank by 
>applying too much vacuum, but that may be an urban legend.

No actual experience with a gas tank .... but I can assure you that
15 - 20 " Hg will collapse a gas tank .... I've done 55 gal
drums.  Wanna do sumpin' dumb (besides talking to me???).  Take
a TV picture tube, put it in a 55-gal drum (one that seals with
the ring, where the whole top comes off) and shoot it with a
.30-.30 or such ..... it'll collapse the drum.  Almost as much
fun as the time we rolled the old Plymouth off the cliff (hee-hee)

Tom Cloud <cloud at peaches.ph.utexas.edu>