rustystud
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First off get your meds checked. Second, I agree with what you said. That is why if that valve is "stuck" """""" open then it will allow the fuel to """"bypass""" the hydraulic head not allowing enough fuel to compress as there will not be any fuel """"" . So basically you just said what I've been saying in two posts now.The "over-flow" valve has a "hole" in it to "always" allow some fuel to "flow" through "it" when there is "pressure" in the "system" from tank "pump" or "boost'' pump. So "when" the "truck" is just sitting "there" engine "off" then would it "not" seem that "there" would be "no" pressure "to" hold back "till" the engine "started" and in tank "pump" not working? The "plunger" makes "the" pressure right "and" the "delivery" valve holds the "pressure" till the "plunger" gets the "fuel" compressed to a "certain" pressure with "what" fuel is just "sitting'' and "held" in "place" because "the" "fuel" line ''that" is coming down "from" the "final fuel filter" going to the "Head" and then "back up "to'' the "secondary" is just sitting there with no "pressure" but "full". "Yes" "truck" will "not" "start". Sorry right "index" finger "has" a "twitch'' '' '' '' '' '' ''.
So to recap and on my meds so my finger does not twitch. From what is in the TM and what I understand the over flow valve is there to keep the boost pump pressure at around 60 psi at high idle no load in the fuel control area for the "plunger" (oops meds not working) and it will fully open at 70 psi so as not to over pressurize the head and blow out any O rings. When we turn on the in tank pump the small hole or orifice in the over flow valve will allow small amount of fuel to run through the head and back to the tank. With the small hold there any pressure is lost in the system when the engine is off.
Without the over flow valve the head would never see the sixty pounds it needs to operate at peck performance.
Now, like I said in my first post this is just speculation. Just throwing out ideas to check.
Or does that trouble you ?
After reading your post again I see your not on the same page as me at all. Your talking about the "relief" valve in the filter assembly aren't you. I'm talking about the hydraulic head relief valve. Either that or your confusing the two. Since the "fuel filter" relief valve controls the maximum pressure of 60 PSI .
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