With regard to the debate between JetStarBlue and CafeenMan on whether there can be a time lag as fluid moves through a tube:
I have literally just finished reading a book about the Stealth Fighter (David C. Aronstein and Albert C. Piccirillo "Have Blue and the F-117A: Evolution of the "Stealth Fighter", American Inst. of Aeronautics and Astronautics Inc., Reston Va, 1997, ISBN 1-56347-245-7) and on page 99 they discuss some problems encountered with the pitot probe system. Quoting Lt. Col. Stan Stiefke, an Air Force engineer who was responsible for several aspects of the F-117A program:
The small diameter tubing that was used to convey the pressure information to the actual sensors introduced a phase lag [my italics] in the pitot-static system that eventually coupled into the Flight Control Computer... however, once the pitot tube pneumatic lines were increased in size, the pressure lags disappeared...
So, the possibility of a time delay is indeed very real.
I don't have the details at my fingertips (I can't find the old fluid dynamics textbook just now) but there MUST be a finite time delay between a change at one point in a fluid system and its arrival at another point. The fastest a change in pressure/flow could possibly migrate down a column of fluid is equal to the speed of sound in that fluid, which is not really all that fast. Fluids have viscosity and compressibility which tend to slow their response to an externally applied force. As the example in the F-117A book shows, the diameter of a tube can be an important parameter, and for some combinations of viscosity and diameter distinct and measurable time lags can be observed.
I don't think the delay in a 5 cm length of plastic fuel tubing would be significant, but it might be and without having the equations and data handy I can't say for sure.