CIS fuel line (leak/replacement)

[RNajarian]

Hi gang,

While troubleshooting an issue in my '83 SC CIS motor I noticed the rubber fuel line going into cylinder 2 was cracked and leaking.

I removed the broken line to see it is 9 inches and has a plastic inner tube covered by the rubber sheath.

Can you replace these fuel lines with the all rubber ones you find at an auto parts store?
If yes, is it recommended to secure the line with a hose clamp or will the friction fitting suffice?

Thanks

[RWebb]

IIRC, those are pretty high pressure lines

why not use the stock part?

[RNajarian]

The motor was running when I noticed the leak. It did not appear to be a high pressure line.

Certainly if it a specialized part that's what I'll get but if a regular fuel line would work that is always easier.

[HarryD]

The lines are rubber coated nylon.

You will need to get the Nylon line. Rubber lines expand and contract with injector opening and closing and your car will run poorly. Several years ago a fellow tried using thinner wall nylon tubing tothis application and had surging, the rubber lines will make it worse.

You have two options, get replacement nylon lines or some metal lines.

[RNajarian]

Well now I've been schooled . . .

On to the parts portion of the forum. What is the inner diameter, 6mm or 8mm?

Thanks for the help

[Flat6pac]

The 83 should have steel lines from the factory..
Bruce

[psalt]

There must be more to the story, it should have steel lines. Some flexible line parts can be found here;

CIS LINE & FITTINGS

[RNajarian]

The other 2 cylinders on this side (number 1 and 3) are steel all the way. Cylinder 2 is steel up until 9 inches from the cylinder when it connects to flexible high pressure hose, inside diameter 6mm.

[HarryD]

Sounds like ther was a repair done at some time and they spliced an earlier nylon tube to the original hard line.

[psalt]

The other 2 cylinders on this side (number 1 and 3) are steel all the way. Cylinder 2 is steel up until 9 inches from the cylinder when it connects to flexible high pressure hose, inside diameter 6mm.

That sounds like the pressure line to the WUR to me.

[RNajarian]

Not an expert on the CIS. The steel line coming out of the fuel distributor looked like the other five (color/aging/connections.) If I had to bet I would say this was the stock setup, but I could be wrong.

The hardware posted in the link in post #7 looks like the hardware I'm using.

QUESTION

Inside Diameter of 6mm on this high pressure hose,

does it measure inside diameter of the rubber hose (which is 6mm)
or
does it measure inside diameter of the nylon hose (which is 4mm)?

[psalt]

The stock set up has steel lines with nuts going to the 6 injectors. The pressure line from the FD to the WUR is steel from the center of the FD, changing to rubber a few inches from the WUR. It is NLA.

[RNajarian]

I'm trying to track down the high pressure hose, no luck yet. I wonder if there is a steel line on my 1975 2.7 setup I can scavenge.

I called a local shop which puts the high pressure flexible nylon/rubber line on the steel line. Quoted Price $150.

Seems a lot for what i need.

[RNajarian]

NUTS. Just called Pelican and was told part is no longer available. I was told to try a local diesel fuel injection shop . . . $150.

[HarryD]

If you can find them the size is 2mm ID x 6mm OD.

You will find many sources of 4mm ID x 6mm OD Nylon line but the wall is too thin and results in injector pulsing. Read this tale of woe: CIS misfire. Sorry GBStu.

[RNajarian]

Thanks for the measurements.
Here is the bad part.

As you can see the outer diameter is 9mm

The inner diameter (marked by the insulation) is 6mm

The inner diameter of the nylon tube (hard to see in photo) is 3mm

I'm beginning to think I may have to get one custom made at the diesel fuel injection shop.

[BoxsterGT]

This semi-flexible fuel line is called Polyamid or Nylon tube.

If the tube diameter is truly 6mm OD then the only size available today has an ID of 3.15mm and a wall thickness is 1.4mm.

This is rated at a working pressure of 42bars or roughly 600 psi.

I specialize in Porsche fuel & oil systems. I can order this Poly tube for you, however it does not appear to be available with the rubber outer sheath.

I work with these for the early MFI fuel systems.........





It would be best to find a factory replacement, even a used one if still in good condition.

The correct Poly tube is difficult to get & difficult to assemble without specialized tools. The stuff from McMaster-Carr is NOT correct.

I would be happy to assist but please email only, no PMs.

Also, you should check the routing of your lines, as I think cyl #2 should have a steel line, not a combination. The combo line may go elsewhere. Of course, you still need to correct the leak.

Cheers,

Len at Autosportengineering dot com