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1985 Carrera
 
Join Date: Jun 2022
Location: Australia
Posts: 109
CIS Fuel System Lines - Can I just use rubber lines?

Hi Team,

Been searching the forum on replacement fuel lines for the CIS system. I have a 80s SC with the Nylon lines.

My local shop said they dont have Nylon lines to replace it with, but they could just crimp rubber fuel line and remake all the lines.

Now my research on here shows that rubber line should be ok pressure wise @ ~100PSI from the fuel pump.

I couldnt find any advise on why every one was trying to source the original Nylon line or upgrading to Steel.

Please help me to understand what I am missing here? Why cant I just replace all the Nylon lines with Rubber Fuel Injector Line (SAE J30R9).

Thanks!

Old 04-22-2025, 04:33 PM
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My impression from being underneath the car and looking at things is that rubber lines would make the challenging job of routing them through the tunnel even more difficult/impossible.

I’m getting ready to do my fuel lines sometime in the next year and am looking at getting the Mason engineering kit. It appears to replace the plastic tunnel lines with aluminum? But I’m not exactly clear on some things otherwise would have bought it already.
Old 04-22-2025, 04:46 PM
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Location: Philadelphia, PA
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CIS Fuel Lines……….

Quote:
Originally Posted by LBEEMING View Post
Hi Team,

Been searching the forum on replacement fuel lines for the CIS system. I have a 80s SC with the Nylon lines.

My local shop said they dont have Nylon lines to replace it with, but they could just crimp rubber fuel line and remake all the lines.

Now my research on here shows that rubber line should be ok pressure wise @ ~100PSI from the fuel pump.

I couldnt find any advise on why every one was trying to source the original Nylon line or upgrading to Steel.

Please help me to understand what I am missing here? Why cant I just replace all the Nylon lines with Rubber Fuel Injector Line (SAE J30R9).

Thanks!


You need at least 150 psi. fuel injected rated rubber hoses for your CIS. Rubber fuel injection lines rated 100 psi. is too close to a single FP max. delivery pressure in case of flow restrictions.

Tony
Old 04-22-2025, 04:50 PM
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1985 Carrera
 
Join Date: Jun 2022
Location: Australia
Posts: 109
Hi Tony,

For my understanding then. Everything before the fuel distributor can remain as rubber fuel injector hose?

Or am I mistaking the fuel lines around the fuel pump and fuel filter as normal rubber fuel line?

Thanks.
Old 04-22-2025, 05:56 PM
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Location: Portland, Oregon
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Read this thread. Pay attention to Post 13 as it is informative about the nylon lines. https://forums.pelicanparts.com/porsche-911-technical-forum/236328-cis-misfire.html
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Harry
1970 VW Sunroof Bus - "The Magic Bus"
1971 Jaguar XKE 2+2 V12 Coupe - {insert name here}
1973.5 911T Targa - "Smokey"
2020 MB E350 4Matic
Old 04-22-2025, 07:59 PM
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Quote:
Originally Posted by LBEEMING View Post
Hi Tony,

For my understanding then. Everything before the fuel distributor can remain as rubber fuel injector hose?

Or am I mistaking the fuel lines around the fuel pump and fuel filter as normal rubber fuel line?

Thanks.
FWIW, my 1973.5 has rubber liners up to the accumulator and steel or nylon after that.
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Harry
1970 VW Sunroof Bus - "The Magic Bus"
1971 Jaguar XKE 2+2 V12 Coupe - {insert name here}
1973.5 911T Targa - "Smokey"
2020 MB E350 4Matic
Old 04-22-2025, 08:01 PM
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1985 Carrera
 
Join Date: Jun 2022
Location: Australia
Posts: 109
I need to figure out where I can get the lines between the accumulator and distributor re built. I see Len does them, but I'm in Australia. Can't seem to find people doing nylon fuel lines anymore.
Old 04-23-2025, 04:00 AM
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Do them yourself. There are a couple threads in the Forum on how to do that. You have to make some simple fixtures to hold the lines and push on the ends, but "search" isn't helping me find them at the moment.
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1973.5 911T with RoW 1980 SC CIS stroked to 3.2, 10:1 Mahle Sport p/c's, TBC exhaust ports, M1 cams, SSI's. RSR bushings & adj spring plates, Koni Sports, 21/26mm T-bars, stock swaybars, 16x7 Fuchs w Michelin Pilot Sport A/S 3+, 205/55-16 at all 4 corners.

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Old 04-23-2025, 10:01 AM
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1985 Carrera
 
Join Date: Jun 2022
Location: Australia
Posts: 109
Yes, I see ************ have the Polymide line in correct size. I think I will take your suggestion and just do them.
Old 04-23-2025, 01:50 PM
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I think Belmetric has all the stuff.

Old 04-23-2025, 02:28 PM
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