Replacing 72T Fuel Line

OkieRon · 10-26-2003, 06:28 PM

I have a 72T that sat garaged for many years. I pulled the gas tank and etched it. Now I am moving onto the fuel line. From a practical standpoint, what needs to be replaced from the gas tank to MFI? (from the tank, the fuel line runs, presumably, into the body to the rear firewall- - -should that be replaced too? if so, how do I get to it)

Any Ideas would be helpful.

Thanks

Ron

73911guy · 10-26-2003, 06:45 PM

This is one of the jobs on my list of things to do this winter. Both ends of mine are showing corrosion. Are you planning on using a factory replacement? If so, what is the part number?

Please keep us posted on what you find out and let us know how tough a job it is.

Thanks

Jim
'73 911

304065 · 10-27-2003, 04:45 AM

Ron and Jim,

Replace ALL OF IT! The fuel line you want is sold by Pelican. It is a German type, rubber with a braided cloth cover. Do NOT settle for anything less, particularly the cheapie domestic stuff. It comes in two sizes, I think, 8mm and 7mm i.d.

The hose runs are like this: from the barb fittings on the fuel tank for supply and return from the MFI system, around the steering box and a swaged connection to the steel hard lines that run through the tunnel. There are two rubber grommets around the end of the hardlines, check them to make sure they aren't weathered or cracked. As far as replacing the swaged fittings, that's probably not possible without a swaging tool, so I'd get some good german hose clamps.

At the other end of the tunnel there are two lines that connect to the steel lines, again. These both run around the port-side heat exchanger and connect again to steel lines that run through the body up to the engine compartment. Then from those steel lines, there are four short hoses that go to the MFI fuel filter console: supply to plenum, output from filter to MFI pump, return from MFI pump to plenum, return to tank.

Somewhere there's a restrictor in one of the lines, but I never found it. The working pressure should be 1-2 bar but the pump will do that on its own without a restrictor.

Working with the fuel lines is a tough job- you have to jack and properly support the car so it doesn't fall on you while you're working under the tunnel- it's almost easier to do with the engine out. But it can be done, and a good factory replacement will last for years and give you the peace of mind of knowing you aren't going to turn into a fireball. . . .

73911guy · 10-27-2003, 05:01 AM

John

My big problem is corrosion on the ends of the steel lines - do you have any experience replacing the hard steel lines in the tunnel?

Thanks

Jim

HawgRyder · HawgRyder's Garage

I'm in the same boat....
Does the steel line have clips inside the tunnel?
Or...will the line slide out if correctly aligned and persuaded?
Bob

304065 · 10-27-2003, 07:19 AM

The steel line is held to the side of the tunnel by metal retaining clips approximately 1" long by 3/8" wide. There are plastic grommets that cover the line to prevent chafing. Also, the line has bends at both ends, making it difficult to slide in and out.

I ran braided aeroquip line through the sub-tunnel within the main tunnel ('71 had this, don't know about later) and it was a royal PITA. If I were going to replace the factory line, I'd get some steel tubing from Jeg's. The lines are available from Porsche, but I think they are all superceded parts, e.g. they fit the 87- Carreras but differ from the early cars (if I recall a post by Roland Kunz from years ago correctly).

I wouldn't put rubber line in the tunnel, too much stuff to chafe against (shifter, throttle, clutch) and stay the heck away from the starboard side of the tunnel entirely (that's where the electrical cables run!)

Good luck all.

OkieRon · 10-27-2003, 09:23 AM

Thanks John,

How do you tell if the steel line running the length of the tunnel needs to be replaced or better yet does not need replacement?

Thanks
Ron

OkieRon · 10-27-2003, 09:46 AM

One more question. What fuel Line do you use. PParts lists "High Pressure Fuel Hose"-7mmIDiam/12mmODiam and 8 ID/13 OD.
They also list "Fuel/Vacuum Hose" with sizes from 3.5mmID to 14mmID.

Which do you use for 1) bottom of gas tank to steel hard lines 2) engine compartment lines 3) fuel filter assembly 4) MFI hoses (they are all cracked and deteriorated) 4) Any other applicable lines.

Jay Auskin · 10-27-2003, 02:34 PM

It's my understanding that the high pressure fuel hose is for the CIS system as the transfer pump is a fairly high pressure. The MFI system only produces what would be considered "high pressure" after the MFI pump which is where your steel lines are that connect to the injectors.

OkieRon · 10-28-2003, 07:22 AM

Thanks Jay,

Now, what size hose is appropriate for which areas?

Thanks

Early_S_Man · 10-28-2003, 08:53 AM

Ron,

The diagram below may be of some help.

The supply line from tank to pump is 9 mm ID for both rubber hoses. An available nominal 3/8" OD USA-made steel fuel line should work to replace the supply line through the tunnel.

The rubber pressurized lines from the pump are all 7 mm ID, including the return line in the tunnel, which is 7 mm OD steel ... a USA-made replacement in 5/16" should also work.

The following link is to search results on "mfi fuel hose" ...

http://forums.pelicanparts.com/search.php?action=showresults&searchid=460087&sortby=lastpost&sortorder=descending

JSDSKI · 09:39 AM

Warren, thanks for the parts diagram. Two other questions:

a) How long a piece of 7mm and 9mm is needed to change out all the rubber hose with new?

b) A tech told me to wipe down steel line with Loctite before slipping a rubber hose over it. It would help the rubber slip on and seal it better.

Opinions?