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There is a check valve built into the fuel pump. The only difference with some of the older cars AFAIK is that the pressure regulator is removable from the filter on some of the older ones.
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1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) |
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Ok, so then my 2 yr old Delphi fuel pump could be the culprit. Its also only putting out 40psi at the rail, so maybe I need to spring for an OE BMW part. I seem to recall 50psi is the magic number but will look in Bentley.
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Current Original owner 2002 E53 X5 4.4i to 4.6i swap 2025 G06 X5 50e Former 1972 Audi Fox 1986 Saab 900S 1996 BMW Z3 1998 BMW E36 M3 Sedan 2004 BMW E46 M3 2006 Audi A3 Quatro 1993 Mopar 318 Jeep Grand Cherokee 2015 V6 Jeep Grand Cherokee |
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Maybe you need a better fuel pressure gauge or connection? The pump check valve is the most common point of leaking fuel pressure but the regulator, injectors and all the lines and connections need to hold as well. Maybe start a thread if you want to look into this further?
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1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) |
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50 is the magic number. If you FPR comes off like mine did you might find a leaky o-ring that vented the pressure back to the tank.
When check valve holding you should have 20-30 psi overnight but the FPR o-ring also must seal.
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
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Sounds good, thanks Andrew. But where is the FPR on the smaller (older, I think) filters like in the picture above? It isn’t a separate part, so is it part of the pump?
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Current Original owner 2002 E53 X5 4.4i to 4.6i swap 2025 G06 X5 50e Former 1972 Audi Fox 1986 Saab 900S 1996 BMW Z3 1998 BMW E36 M3 Sedan 2004 BMW E46 M3 2006 Audi A3 Quatro 1993 Mopar 318 Jeep Grand Cherokee 2015 V6 Jeep Grand Cherokee |
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Bummer i think it's built into the filter. You could confirm the problem is in the pump or the FPR by pinch off the return line. There's a TSB on the exact procedure but if i did it i would have a helper so i can pinch the return line as soon as i turned off the key. Or: i think foxwell can engage the pump. If your pump primes on key on you can listen for it to stop after ≈ 6 seconds. The check valve is in the pump. If pressure stays with the return line pinched the problem is like mine was: internal leak at the FPR draining. If it still drops it'll be the pump check valve. If the pump check valve fails but the pump is ok, people will often just add an inline check valve.
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
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First look into why you have only 40 PSI of fuel pressure.
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1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) |
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Well boys and girls, it's that time again (2.5 yrs ) so the 1st parts are in....
Front was a couple of months ago, along with brakes, tires, fluid/filter change and hood cables/latches. Sent from Embassy network using Tapatalk
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"When the Team Chief said.... You're trapped in a hole with nothing but a goat and a slinky, what do you do? Stubby said, I'm not sure but it won't end well for the goat...." ~(Overheard) Last day, Phase 3, Q Course |
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