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Fuel system nightmare! My Boxster used to run so well...

Go to solution Solved by JFP in PA,

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  • 2 years later...
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On 1/16/2013 at 1:38 PM, JFP in PA said:

That is pretty much how the system functions. You should have as much fuel delivery at the return line as at the filter. While we are on the subject, have you checked your fuel pressure regulator for being involved in the noise you hear at start up? Reason I ask is your earlier comment about the fuel pressure swinging from high to low and then building back up sounds like it could be some sort of blockage, or it could also be related to the pressure regulator opening and abruptly closing when it should not be doing that:

pressure regulator.png

While I hate to be throwing in more possibilities at the 11th hour, if the regulator were to "dump" the fuel rail pressure, nearly all the fuel volume would suddenly be passing into the return line, which could be the source of the sound you hear as it heads back to the tank. Unfortunately, there are very few tests to check the regulator, but one common rule of thumb is if If the operating pressure is below 35psi, or fluctuates wildly, and the fuel pump seems otherwise fine, it’s probably a good bet that the regulator is bad. If you pull off the vacuum connection and there is fuel dribbling from the nipple, the diaphragm inside has failed and the regulator must be replaced. The fuel pressure regulator could also explain why the return delivery rate is so low.


Just to be extra clear, the fuel return line is directly under the regulator in this picture, #8, correct? Fuel supply is on the opposite side. 

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On 7/4/2017 at 4:01 PM, 3.2ina996 said:


Just to be extra clear, the fuel return line is directly under the regulator in this picture, #8, correct? Fuel supply is on the opposite side. 


That is correct


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  • 2 years later...

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