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Old 04-07-2021, 03:19 PM   #1
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Fuel supply and return which is which?

This is a bit of an embarrassing question that I could have answered myself if I still had the original engine in the car but does anyone know what is the fuel supply and what is the fuel return line? I shamelessly stole this photo off another thread so if its your photo thanks.



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Old 04-07-2021, 03:23 PM   #2
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Can't answer from the pic, but the fuel filter is close by. Trace from there?
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Old 04-07-2021, 05:19 PM   #3
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I`m pretty sure the right one is the return line.
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Old 04-08-2021, 02:35 AM   #4
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I would think but don't know that the larger line ( blue arrow ) is the supply and the smaller is the return . Hopefully someone smarter than me will chime in .
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Old 04-08-2021, 06:56 AM   #5
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Man I should have made this a poll!
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Old 04-08-2021, 08:32 AM   #6
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The one with the blue arrow should be connected to the fuel pressure regulator on the injector rail, and should be the feed line on a 97.

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Old 04-08-2021, 08:47 AM   #7
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The one with the blue arrow should be connected to the fuel pressure regulator on the injector rail, and should be the feed line on a 97.

The fuel pressure regulator is installed on the feed line on Porsches? How does that work? Now I'm really confused.
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Old 04-08-2021, 08:52 AM   #8
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The fuel pressure regulator is installed on the feed line on Porsches? How does that work? Now I'm really confused.
On the early cars, it was a vacuum operated diaphragm device on the fuel rail, as in the diagram.



The early fuel system included a return fuel line and had a fuel rail mounted fuel pressure regulator. For 2002, there is no return fuel line and the fuel pressure regulator is mounted in the fuel tank.
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Old 04-08-2021, 09:14 AM   #9
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OK, seems after checking the early service manual, I have the lines reversed: The fuel pressure regulator in on the return line. Sorry bout that......��
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Old 04-08-2021, 09:14 AM   #10
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Quote:
Originally Posted by JFP in PA View Post
On the early cars, it was a vacuum operated diaphragm device on the fuel rail, as in the diagram.



The early fuel system included a return fuel line and had a fuel rail mounted fuel pressure regulator. For 2002, there is no return fuel line and the fuel pressure regulator is mounted in the fuel tank.
Right, but typically these regulators are installed after the rail to ensure they are maintaining rail pressure (unless I’m wrong). Do I have this backwards?
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Old 04-08-2021, 09:17 AM   #11
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See my previous post; seems my memory is not as good as it once was, but the service manual's always is................
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Old 04-08-2021, 10:26 AM   #12
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See my previous post; seems my memory is not as good as it once was, but the service manual's always is................
Great thanks! I really need to get one of those service manuals and stop abusing you guys. thanks for all the help.
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Old 04-08-2021, 10:37 AM   #13
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I think the question was also wrong So, just to clarify, the right one that runs from the regulator is the return line. The left one (red) is a vent line. The feed line is not pictured, it is on the other side of the rail and is coming up from the fuel filter on the right side of the car. At least on mine, which is a 99 Base.
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Old 04-08-2021, 02:11 PM   #14
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I think the question was also wrong So, just to clarify, the right one that runs from the regulator is the return line. The left one (red) is a vent line. The feed line is not pictured, it is on the other side of the rail and is coming up from the fuel filter on the right side of the car. At least on mine, which is a 99 Base.
Ha! What a rollercoaster. Join us next week for: What are these “coolant” lines?
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Old 10-15-2021, 12:35 PM   #15
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My fitting at the blue arrow is slightly wet/weeping. Does anyone know whether there is an o-ring in the disconnect fitting that can be replaced? Other options of repair? And my vote is that it (blue arrow) is the return line (98 base)
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Old 10-15-2021, 04:53 PM   #16
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My fitting at the blue arrow is slightly wet/weeping. Does anyone know whether there is an o-ring in the disconnect fitting that can be replaced? Other options of repair? And my vote is that it (blue arrow) is the return line (98 base)
Mine was leaking too, but not at the connector, but at the fuel rail, and it was leaking down on the back side of the line. If it leaks at the connector, it`s also possible that the line itself is scratched where the fitting slides onto.

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