I've done a search on this topic but couldn't find what I'm looking for. I'm not questioning "if" this setup works but rather "how" it works. As I understand it, by cutting a bypass loop into a lift pump setup it will enable you regulate/restrict fuel flow through a looped section with the use of a needle valve, allowing you to make final pressure adjustments at the schrader valve up front. What I don't understand is how is the flow regulated when you have a pump inline ( on the main feeder line)with an output pressure of about 4PSI and a looped line and needle valve with a negative pressure ( fuel being drawn by OEM fuel pump) all tee'd together on a common input/output line. Is the postive flow on the output side of the pump cancelled by the negative flow caused by the needle valve and how does this system stay pressurized when fuel demand exceeds 4 PSI? Does it then become a vaccum system again at this point? Just trying to understand some of the theory here http://www.dieselplace.com/forum/smileys/Geek.gif sorry about the long winded question.


Thanks in advance


Terry
Edited by: TC Dmax

<DIV>The needle valve bypass was a method of reducing the amount of pressure a lift pump would put out to the engine diesel pump. It is</DIV>
<DIV>not regulated. The only regulation is that as the pressure increases</DIV>
<DIV>more fuel will flow past the needle valve thus releasing some of the </DIV>
<DIV>pressure head the lift pump puts out.</DIV>
<DIV>I am running without a bypass with no problems. The EP 309 pump is </DIV>
<DIV>supposed to be a regulated pump and from past postings seems to have an output pressure of from 4psi to 6psi (Not tested). This should in no way harm the Engine diesel pump. As you increase your</DIV>
<DIV>power use the pressure will drop down to where you have very little </DIV>
<DIV>increased pressure.</DIV>
<DIV>I am also not using a timer with my lift pump. My final filter is in the </DIV>
<DIV>2nd Alternator position which is above the engine diesel pump thus</DIV>
<DIV>putting about 3+Ft of full fuel line above the engine diesel pump. I have instant starts http://www.dieselplace.com/forum/smileys/Approve.gif Also remember there is a check valve in the</DIV>
<DIV>OEM filter to hold the fuel that is there at shutdown.</DIV>
<DIV>Hope this helps to explain your questions.</DIV>