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These fuel lines are certainly well past service life. When taking into consideration exposure to alcohol (e10) and heat it's amazing they've done so well. Props to OP for reminding us all to address a safety issue.
I've been researching fuel hose replacement for a '97 993, Looking at available factory replacement hoses, they are using 6255-Cohline-3124 8mm hose, which is a rubber armored Polyamide hose. The hose is available from Bel-Metric (RHPOLY8x14), as are the collars and some conical end fittings. I have found several links to AN hose kits, refurbishing services or shops that will crimp new PTFE hose on existing fittings. What I have not found is any information about the expected service life of a Polyamide (Nylon) fuel hose. Which brings me to my question. Rubber hoses have a service life of no more than twenty years (assuming proper composition for fluid type). PTFE is advertised as for the life of the car. So what about factory specification Cohline 3124 Polyamide hose?
How did you determine that the factory is using 6255-Cohline-3124? I found this information timely as I wanted to re-plate my fuel rails and went ahead and ordered the RHPOLY8X14 from Bel-metric to replace the piece of hose between the rails.
I just received it and it's undersized. After removing the stock hose between the fuel rails (and cutting it at mid-point to get a good caliper reading), it reads 8.9MM ID and 15.5MM OD. The item you mentioned actually measures 7.6MM ID and 13.8MM OD. The polyamide lining on the item you spec'd is also half the wall thickness of the stock line, so I don't think this is the correct replacement line.
I don't see a 9MM polyamide with rubber insulation on Bel-metric but I do see this Cohline 9.3MM x 15.3MM option (without polyamide lining) but it does say 100% ethanol safe, so I presume it is a superior modern alternative. Also, given the "8MM" line actually measured 7.6MM ID and was undersized by .4MM, I'm going to assume the "9.3MM" line will actually measure the same 8.9MM ID I measured from the stock line.
Colin @NineMeister also mentioned in post #7 that they use 9MM line for 993's. Colin, any thoughts on the 9.3MM x 15.3MM line I linked to? I'm just looking to replace the fuel line on my 993 between the fuel rails. Unlike the turbo, which has a line with fittings between the rails, I have an NA 993 which has barbs built into the fuel rails and the hose just slides on. Seems like the correct size, made for fuel and ethanol safe so I'm thinking it ticks all the boxes here?
One question, I assume the fuel rails are metal. Do they need replacement and if so why?
The 993 fuel rails are metal and will be good, it's the fuel line connecting the two rails which is the problem. The rails come factory assembled with the hose, hence you can only buy new rails with hose from Porsche.
How did you determine that the factory is using 6255-Cohline-3124? I found this information timely as I wanted to re-plate my fuel rails and went ahead and ordered the RHPOLY8X14 from Bel-metric to replace the piece of hose between the rails.
I just received it and it's undersized. After removing the stock hose between the fuel rails (and cutting it at mid-point to get a good caliper reading), it reads 8.9MM ID and 15.5MM OD. The item you mentioned actually measures 7.6MM ID and 13.8MM OD. The polyamide lining on the item you spec'd is also half the wall thickness of the stock line, so I don't think this is the correct replacement line.
I don't see a 9MM polyamide with rubber insulation on Bel-metric but I do see this Cohline 9.3MM x 15.3MM option (without polyamide lining) but it does say 100% ethanol safe, so I presume it is a superior modern alternative. Also, given the "8MM" line actually measured 7.6MM ID and was undersized by .4MM, I'm going to assume the "9.3MM" line will actually measure the same 8.9MM ID I measured from the stock line.
Colin @NineMeister also mentioned in post #7 that they use 9MM line for 993's. Colin, any thoughts on the 9.3MM x 15.3MM line I linked to? I'm just looking to replace the fuel line on my 993 between the fuel rails. Unlike the turbo, which has a line with fittings between the rails, I have an NA 993 which has barbs built into the fuel rails and the hose just slides on. Seems like the correct size, made for fuel and ethanol safe so I'm thinking it ticks all the boxes here?
I'll have to sit on the fence here as I am no expert in the suitability of different fuel hoses. My recommendation is to go to a renowned hose supplier who understands the application, give him the hose tail diameters and let them recommend a suitable hose for E10 or similar. This is the process we used and we're happy with the choice they made. Sorry that I have to be vague, but I'm sure you understand the implications should I not be 100% correct.
Understand your position and didn't intend to create a liability issue for 9M.
That said, the hose I mentioned seems to be the correct size hose offering from COHLINE and is 100% ethanol safe. Looking at the specs, it's designed to the following standards:
BMW GS 93010 DBL 6256.70 GME 08 007 SAE J30R9 VW TL 524 24 DIN 73379 Type 3E
Should be here in a few days. Will report back if my 993 burns to the ground.
I've been researching fuel hose replacement for a '97 993, Looking at available factory replacement hoses, they are using 6255-Cohline-3124 8mm hose, which is a rubber armored Polyamide hose. The hose is available from Bel-Metric (RHPOLY8x14), as are the collars and some conical end fittings. I have found several links to AN hose kits, refurbishing services or shops that will crimp new PTFE hose on existing fittings. What I have not found is any information about the expected service life of a Polyamide (Nylon) fuel hose. Which brings me to my question. Rubber hoses have a service life of no more than twenty years (assuming proper composition for fluid type). PTFE is advertised as for the life of the car. So what about factory specification Cohline 3124 Polyamide hose?
The cost of materials is minimal, and if the engine or lines where already removed I would plate the fuel rails and install new hose. However, the effort to R&R the lines/hoses on an otherwise in service car is not minimal. The car has 69,000 miles on it, and not burning oil. It is possible the engine will not be out again until 100,000 miles, for a top end. Will the fuel hoses last long?
Lots of info in the 928 forum around fuel lines, as most of those cars where made before the introduction of Polyamide lined hoses, and there has been fires. What is the experience of 993 brain trust? Are these cars experiencing fuel hose failures, aside from physical damage related to service work?
Thank you, Alan
IMO this ought to be a standard "while you're in there" line item when doing an engine out service.
My car had a bad fuel smell when I first bought it. At first I thought this was the standard 993 smell, but it was more acrid and gasoline tinged than the standard oil/leather 911 smell. I replaced the fuel cap and funnel and tightened up all the clamps in the frunk. When I later had the engine out, I asked my shop to replace the rubber fuel lines.
They found a pinhole in one of the lines that had a leak. Since replacement, the smell is gone. Honestly, it's a little freaky to think I was bopping around with a fuel leak, however small it was.
I suspect any 993 with original fuel lines has some degree of degradation and replacement is an inevitably. Just a question of when.
You're on the money to bring up the issue of fuel lines Alan. In my experience we're already past the life of factory fuel lines and without question every 993 engine build at Ninemeister is now having the fuel lines re-manufactured as part of the job.
With the fuel lines off the engine there are two simple tests you can carry out to judge whether the line is safe to use:
1. The first test is to attempt to grab the end fittings with your hands and attempt to rotate the ends within the crimps. If they rotate there is insufficient crimp force and they should be replaced.
2. The second is to bend the rubber lines, testing them for rigidity and inspecting the length of the pipe for surface cracks. Any evidence of excessive stiffness or cracking and they are toast. Worst case, you bend them and they break in half, like the ones below.
Our solution is to re-manufacture the lines by removing the fittings, re-plate to the original yellow zinc passivate finish then machine crimp on a replacement, double braided synthetic rubber hose that is E5/E10 and race fuel compatible.
This 993 turbo pipe failed the bend and crack inspection test As did the one from the other side We have the original end fittings re-plated Replacement hose are machine crimped Restored set for a 964 engine New hose is exterior braided
On another forum, there’s a thread from late 2020 about fuel lines that includes a service bulletin which states two interesting things relative to this thread: 1) the rubber-covered polyamide tube (not hose)should not be bent or else it will damage; and 2) the sleeves, which I think are being referenced as crimp ends above relative to the twist test, are loosely installed and simply serve as stops.
Revisiting this. If I understand correctly, NA 993s have the hose slip-on, with NO crimping. Therefore, no special tools are needed AND only the correct hose needs to be located. So, @boomboomthump , did that hose work (Bel-metric; Cohline 9.3MM x 15.3MM option (without polyamide lining)? Can a length of hose be ordered and then just cut to length?
No, I wouldn't say that is exactly accurate. A few things... (assuming we are just referring to the fuel line between the fuel rails)
True, NA 993's do not have crimped connectors on the fuel line which connects between the fuel rails (the turbo's have different fuel rails where the fuel line has a threaded end and crimped connection). That said, the fuel line does not simply "slip-on" or require "no special tools". See some of the notes in the photo directly above your post. It states that the polyamide hose is attached "with great force during the manufacturing process".
I replaced that polyamide line with a modern fuel hose (noted above). It's a tight fit on the fuel rails but I used a heavy duty, high pressure crimp clamp to ensure it won't go anywhere. Note: I have not run this yet (car still in pieces; finally dusting off this project).
Here is a pic that shows the line + clamp. Also one end where I hadn't attached to the other fuel rail yet and you can see the barb. Clamp is a yellow zinc plated Oetiker 18.5MM clamp. Link to BelMetric.
Last edited by boomboomthump; 01-15-2024 at 12:55 AM.
11-14-2021, 02:16 PM
