Since there are some people that are much smarter than me on here(not saying much, I know), can anyone explain to me why pressure is/is not directly proportional to volume. The reason I ask is, since I work on cars I frequently check fuel pressure. I hear people say that you can have good pressure, but the volume may not be enough. This makes no sense to me, if you have the correct pressure then how could you not have the volume? When I say volume, I am not refering to the actual flow from an orifice, but the amount the pump can provide. I can find references to Boyle and Charles on the internet, but these seem to deal with gases, not liquids.