Go Back   986 Forum - for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Performance and Technical chat

Reply
 
LinkBack Thread Tools Display Modes
Old 04-07-2021, 03:19 PM   #1
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 914
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.



__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 04-07-2021, 03:23 PM   #2
Registered User
 
911monty's Avatar
 
Join Date: Oct 2014
Location: California Central Coast
Posts: 1,394
Garage
Can't answer from the pic, but the fuel filter is close by. Trace from there?
911monty is offline   Reply With Quote
Old 04-07-2021, 05:19 PM   #3
Registered User
 
Join Date: Oct 2018
Location: North Cali
Posts: 442
Garage
I`m pretty sure the right one is the return line.
Homeoboxter is offline   Reply With Quote
Old 04-08-2021, 02:35 AM   #4
Registered User
 
Join Date: Dec 2013
Location: Dahlonega , Georgia
Posts: 1,274
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 .
__________________
2002 Boxster S Arctic Silver with black top with glass window and black leather interior. Jake Raby 3.6 SS ( the beast ) with IMS Solution. 996 GT3 front bumper , GT3 rocker covers and GT3TEK rear diffuser and Joe Toth composites rear ducktail spoiler .
rfuerst911sc is offline   Reply With Quote
Old 04-08-2021, 06:56 AM   #5
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 914
Man I should have made this a poll!
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 04-08-2021, 08:32 AM   #6
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,571
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.

__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein

Last edited by JFP in PA; 04-08-2021 at 08:35 AM.
JFP in PA is offline   Reply With Quote
Old 04-08-2021, 08:47 AM   #7
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 914
Quote:
Originally Posted by JFP in PA View Post
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.
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 04-08-2021, 08:52 AM   #8
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,571
Quote:
Originally Posted by truegearhead View Post
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.
__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein

Last edited by JFP in PA; 04-08-2021 at 08:57 AM.
JFP in PA is offline   Reply With Quote
Old 04-08-2021, 09:14 AM   #9
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,571
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......��
__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
JFP in PA is offline   Reply With Quote
Old 04-08-2021, 09:14 AM   #10
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 914
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?
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 04-08-2021, 09:17 AM   #11
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,571
See my previous post; seems my memory is not as good as it once was, but the service manual's always is................
__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
JFP in PA is offline   Reply With Quote
Old 04-08-2021, 10:26 AM   #12
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 914
Quote:
Originally Posted by JFP in PA View Post
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.
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 04-08-2021, 10:37 AM   #13
Registered User
 
Join Date: Oct 2018
Location: North Cali
Posts: 442
Garage
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.
Homeoboxter is offline   Reply With Quote
Old 04-08-2021, 02:11 PM   #14
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 914
Quote:
Originally Posted by Homeoboxter View Post
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?

__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -8. The time now is 11:31 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page