Fuel pump questions

[Mark Eidson]

Text item: 

Here is another way to look at it:

The closed loop system is like a siphon.  There is no flow between reservoirs 
with fluid at the same height no matter where the siphon lines are in the 
respective reservoirs.  If both lines are submerged in the same tank no flow 
will occur unless the pump moves the fuel because the difference in height of 
the lines equals the difference in height of the fuel.  If the return is above 
the fuel the pump has to do the additional work to move the fuel to the higher 
level which then falls into the tank dissipating that energy.  When the pump 
stops the fuel will partially run back into the tank thru both lines from the 
highest point in the system if there is no check valve.  If there is a check 
valve then the fuel in the return line may eventually partially drain back into 
the tank from the highest point as vapor enters the system thru the exposed 
return line.

me
______________________________ Reply Separator _________________________________
Subject: Re: Fuel pump questions
Author:  diy_efi-owner at esl.eng.ohio-state.edu at SMTPGATE
Date:    12/9/97 12:55 PM


> The return line pressure is based on the vertical distance the fuel 
> is pumped, not the weight of fuel in the tank.  So there would be
> more pressure if the fuel were returned to the top of the tank . 
> Most gas tanks are lower than the high point of the system so the 
> return line is down hill.
>
> Bob McKnight phx az


So you mean to tell me that you can just as easily pump water up a 3/8" 
pipe 75' straight up and into the bottom of a water tower and that 3/8" 
line will have LESS pressure on it than the same line going to the top 
of the water tower and dripping in through the top?  I've been wrong 
before, but I really don't think this is right.

If you put the fuel return line into the bottom of the tank, wouldn't 
that be just like pinching the line and creating more pressure?  Or the 
same as using a smaller fuel line diameter?

Please do explain to me as i don't really understand this i guess...

--
Andy Quaas
p.s. !!!!NO FLAMES INTENDED!!!!

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