onevoice

I was under the hood and noticed a fuel line with age cracking. Going along with my theory of anything worth doing is worth overdoing, I am replacing every piece of rubber fuel line in the car. I will write up a post about things to watch when doing it later, but now I need an answer about the direction the fuel pump faces. I have a 1990, left hand drive. Needless to say, some of the hoses are crazy expensive, so I am looking at replacing the rubber parts only, i.e. Having new hose crimped on the original steel lines. The only hose that I was looking to buy new is the suction line from the tank to the pump, because is has so many tight bends it would be impossible to replicate from straight hose.

The PET has different hoses for 91 and down, vs 92 and up. The early hose from the tank to the pump, 96420158101, is almost $200. The late hose 96420158103, which is supersceeded by -04 is less than $30. The picture I have found of the late hose looks like it must come into the pump from the left, vs the one on my car which comes in from the right.

All the cars use the same pump, so does anyone know which side of the car the line from the tank enters the pump on a 1992+ car. I will be replacing the output line anyway, so it would by much cheaper to get the later input line if that is the case. Did they turn it around on the later cars? The pet drawing appears to show it entering from the right, but the drawing wouldn't necessarily have been updated with a change, just the parts list.

onevoice

Since no one immediately knew the answer, I did some more investigating.

A 993 uses the the same p/n line from the tank to the pump as a late 964, and the same p/n for the pump. The pet diagrams of the fuel line from the tank to the pump for the 993 are unchanged from the 964, but the diagram of the line going to the back of the car clearly shows the output of the pump on the right side.

So, I will go ahead and order the late part. Then, when redoing the line from the pump to the engine compartment, make it long enough to loop around the pump, and then install the pump facing the opposite direction. Much simpler line routing.

Rocket Rob

Sorry I can't add anything but am curious what you learn. Please circle back when you have completed the project. Thx.

Super90

I did a little research on this while I had my engine bay apart a bit ago. I've already forgotten quite a bit but in summary, we found that the polymide hoses were all in really good shape. We took a couple off and dissected them to see how they were holding up and concluded it wasn't worth replacing them. Those were the hoses in the engine bay by and large. There are some hoses on the ends of hard fuel lines that are not polymide, they lead to and from the engine bay and are worth careful attention.

This was in keeping with what Len Cummings findings are. He can be found on the Pelican boards and routinely builds replacement hose assemblies for customers. It seems Porsche got it right with the Polymide hoses application, which I believe was new as of the 964 line, but someone else will know better.

I can dig up more info in a few days when I return from traveling.

onevoice

I plan on writing up everything I learn while doing this project. I could not find a definitive answer to the question of what the material the hoses are made out of. I have read that some are not degraded by commonly available fuels and their ethanol content, but several of mine showed cracking and obvious degradation. The thing that also concerned me was that several crimped connections could be rotated around the fitting, indicating that the connections had lost much of their preload. Even without knowing the exact specification of the hose material, it is known that many types of "plastics" will cold flow and harden over time. It stands to reason that with the lines approaching 30 years in age, replacement is a safe bet. I can't think of much more terrible happening to my car than watching it burn on the side of the road.

I just returned from the local Porsche dealer, and my earlier supposition was correct. They had a 993 on the lift, and it had the fuel pump cover removed. The fuel line from the tank enters the pump from the left, and the fuel to the engine exits the pump on the right. Routing the hoses this way lets them have much more gentle bends. The pet says 91 is the changeover, but no indication if that is a strict model year changeover or if it was a gradual change. Best to visually check if you have a late 91 or early 92 model.

onevoice

Just to give a visual, this is how many lines are in the engine compartment. Plus the lines that go forward have flexible sections also. Altogether, a rediculous arrangement that is simplified on the 993.

onevoice

I am finding there is a lot more to fuel lines than "rubber" and "plastic", and they have come a long way from the old days. The word Polyamide means a macromolecule with repeating units linked by amide bonds. Natural ones are proteins, the most common synthetic one is the group of nylons. It is not enough to refer to fuel lines as polyamide, because they can have many different characteristics. The original lines on my car have the brand name Cohline, looking up their data sheets I found 7 different types of fuel hoses, none of which actually say polyamide. There are various ratings of temperature, pressure, abrasion resistances, ethanol contents, biodiesel compatibility, etc. From a domestic manufacturer, Gates, there are comparable hoses that meet SAE and CARB permeability standards. It gets pretty involved quickly, and of course Porsche doesn't say what their replacement hoses are either. To complicate things further, some polyamides, while not alcohol absorbent, have been found to soften under prolonged exposure.

To make a long story short, the polyamide lining might not be the problem at all in fuel lines, but as the outside rubber (usually for abrasion resistance) coating ages and deteriorates, the clamping force from the crimp goes away. Then it leaks, and if you are unlucky, it causes a 911 bonfire.

I will try to write a more comprehensive post that details the costs involved, that pile of parts in the pic above is more than $1000 for example, and link it back to this posting.

540964

Check with Griff. https://griffiths.com/porsche/air-conditioning/
He was building fuel lines for 964's using the correct hose and proper crimp ferrules.

-nick

I'm not sure about the proper hose material, but you can buy the correct Cohline crimp collars easily enough https://www.belmetric.com/hose-collars-c-14_1319/ Re-use the original hose ends and have any hydraulic shop crimp new collars onto new hose. Or use -an adapters and do it all yourself. Certainly much better than $1000+ for some fuel lines?

onevoice

Yes, I am not buying new hoses from Porsche. The price is absurd. The question is EXACTLY what hose specs are. There are lots of references to "correct" hose, or shops doing it "right", but no one ever says exactly what hose and exactly what spec they are using. Like the reference to polyamide, which seems to be used by non-domestic suppliers like nylon. Lots of different nylons. The other question is whether or not to update the lines to simplify the whole mess like the 993's. They ran a line from the tank to the pump, to the filter, then directly to the fuel rail, then directly to the other fuel rail, the regulator was attached to the rail, then a line to the return. That would eliminate several hoses, and half a dozen connections. Or step into the 21st century and use a regulator/filter/return combination up front near the pump, (similar to millions of new cars) and only one line running to the fuel rail. That would get rid of another 5+ pounds of lines and another dozen or so connections. Dead nuts reliable.

I suspect the crimp ferrules are part of the problem. Especially when used with nylon/polyamide hose with a rubber outer layer. My car has several crimped connections that are loose, i.e. the connector can be spun easily, independent of the hose it is attached to. My guess is that the rubber has deteriorated over time, so the crimp isn't tight any more.

I'm not trying to reinvent the wheel, I just want to know exactly what I am putting back on the car. I've learned a lot about hoses looking this info up, but don't have all my notes ready to make a detailed posting. I will say that from a cost perspective, the options from most expensive to least are, factory replacement parts, converting to AN fittings with Teflon hose, refitting with new hose on factory ends, and converting everything to new style nylon fuel hose. The cost of the most expensive is probably an order of magnitude more than the cheapest. Not to mention that the most expensive option, new factory parts, has the most uncertainty, because you don't know how long those parts have been sitting on the shelf.

cobalt

A little late but I figured I would post a picture of my 93 C2 with 61k miles and appears to have never been touched. I was contemplating changing lines but mine seem to be all good as of now. Soft and pliable unlike the oil lines which get hard and brittle. I do recall when I was pulling my 90 apart they were all cracked but it took a lot of pulling and tugging to get them out and when I did they seemed to survive without leaking. No doubt when cracked replacing is better than taking a chance.

Hopefully the picture will help although you seemed to have answered your question already. Still covered in their original cosmoline and as I am sure you know up is the front of the car.

Good luck.

onevoice

Thanks for the pic, it is exactly like that in a 993. On the early 964s, that line from the tank to the pump makes several more crazy bends and the pump is turned 180degrees in the mount. $200 for 8 inches of rubber line with no fittings!

Truth be told, I could probably get away without changing them for a while, but I have to change the ones that run across the engine top. I had changed them 2 years ago when I rebuilt my engine, had it done by a professional shop that "did it all the time", and used the "best hose" , and guess what, they used high temp and high pressure hydraulic hose, not fuel hose. It isn't rated for gasoline use. I noticed it when i was checking the numbers on the hose while researching hose.

Those aren't the hoses that are now showing issues, but they are definitely getting changed. That is why I am going to know EXACTLYwhat I put back on.

cobalt

Glad I could help. I will check to see if I can find a TSB on changing the early cars over. They say that 85% of the 964 was new over the 3.2C I think over the course of the models life they changed another 35% lol

I see stuff like this all the time. Some shops do whatever is convenient and hate to say it cheap.

JJ964

Cohline Type 3024.0800 (8MM) Rubber covered PA12 (Nylon 12). Should be printed on the old hoses. The return hose on the older engines was made w/ 10MM typ 3024 but is NLA. The replacement line is 8MM.

Super90

There are indeed several shops out there that will tell you exactly what hoses they use to rebuild wth.
Some use Cohline 2134 and others use the higher spec Cohline 2240. Keep digging, the data is out there....