308 F.I. plastic lines to injectors - Weak design?

Did anyone try to source the 6x2 replacement lines made by Cohline from Global Metrics 650-592-2722 ???

The OEM Ref # listed in the Global Metrics catalog is as follows:

ID x WALL x OD -- Ref #
3 x 1 x 5 -- 313 0305
2 x 2 x 6 -- 313 0206

I ended up using 5x3 on my 328 because the 6x2 are impossible to fit

Verell, can you comment further on: The 911 guys reported missfiring only when they were using 5x3
I failed my HC emissions and I'm wondering if this may be an issue?

Carmine

 

Yes I did, as i mentioned above thats the cheapest source for the line. to install the line I heated it with a heat gun and used a brake flare line tool to hold the line while fitting the end, worked like a charm. buy more than you need and practice a bit.

 

Did you use the 6x2 or 5x3?

 

While waiting to hear from Scott on the size he used, I sort of forgot about his post.

I'd really like to know if he was able to insert the barbs into 6x2 by hand.

 

Here's an interesting CIS tidbit I picked up from a SAAB forum, it may be related to the CIS line size problems the 911 guys ran into. (See the 911forum links in my post #8 in this thread.)

Q:"If all the lines out of a K-Jetronic fuel distributor are at the same pressure and have the same flow rate, why not just have a common rail?"

A: "I believe it has to do with response time. I remember years ago a Saab technician told me about a problem he had been chasing.

It turns out that Saab uses plastic fuel line between the distributor and the injector. Two lines had been remade with a common line used for such. The black line used was common to VW and Volvo. The clear lines used on Saab and BMW were half again as big in diameter. He fixed the problem by putting the lines back to original and the factory rep that helped with the diagnosis said that the diameter of the lines changed the quantity of fuel in the line which changed the ability of the fuel to respond to sudden changes in flow rate."

 

Seems like there must be something else going on.

Simple hydraulics using an non-compressible fluid like gasoline, any change at one end should produce an instant equal response at the other end.

 

still diggin for the reciept, I took the original lines with me and matched them up. I still have hose here, these are the sizes I got that matched the line i had, '81 euro mondial.
8x1 cohline - 3011 0608-23-DIN 73378-74324 - 8x1 -PA 12HIPHL
6x1 cohline - 3011 0406-23-DIN 73378-74324 - 6x1 -PA 12HIPHL
5x1 cohline - 3011 0305-23-DIN 73378-74324 - 5x1 -PA 12HIPHL

They are a PITA to install the fittings, I practiced a bit before going for it. I found using the heat gun to soften the line and then quickly fit the barb by holding the line in a brake flare tool worked best. 30k miles later and no leaks.

 

That's true for static sealed systems with neglible restriction to flow between any 2 points.

The K-Jet is a dynamic system with flow restriction. The pressure change is occurring on the other side of a very small orfice (the distributor's slot), then the volume of fluid that has to flow thru the orfice to transmit the pressure change will affect the transient response at the injector. Also, remember that the tube is lossy due to the injector, and that the tube is slightly elastic.

In any case, no matter what the theory, the fact is that changing to the correct tubing type fixed the problem.

 

The line that Scott got from Global Metrics are the COHLINE sizes that seem to be readily available here in the US from multiple distributors. From the COHLINE catalog page I posted earlier, here's what Scott used:

8x1 cohline - 3011 0608-23-DIN 73378-74324 - 8x1 -PA 12HIPHL - This is 8mm OD, 6mm ID, 1mm wall thickness.

6x1 cohline - 3011 0406-23-DIN 73378-74324 - 6x1 -PA 12HIPHL - This is 6mm OD, 4mm ID, 1mm wall thickness.

5x1 cohline - 3011 0305-23-DIN 73378-74324 - 5x1 -PA 12HIPHL - This is 5mm OD, 3mm ID, 1.4mm wall thickness.

Interpreting the cohline numbers:

The nx1 is OD in mm x wall thickness in mm. eg: 6x1 is 6mm OD, 1mm wall thickness

3011 - black polyamide line.
The next 2 digits are the id & od eg: 0406 is 04mm id O6mm OD.
The DIN # is the relevant standard, '-PA 12HIPHL' seems to stand for PolyAmide and some characteristics specified by the standard.




Scott, everything I've been able to research points to the OEM injector line being 6mm OD, 2mm ID, including measuring actual lines. Not sure why your original line measured 6mm OD, 4mm ID. Maybe it had been previously replaced. The line I'm trying to get imported is:

6x14 cohline - 3011 3106-23-DIN 73378-74324 - 6x14 -PA 12HIPHL - This is 6mm OD, 3.15mm ID.

Which is the closest size available to the OEM line.

 

can't say for sure if mine were replaced or not, but its' what was there, looked old and needed replacing. maybe there was a varience at the factory when assy was going on for different markets. I have the CIS basic and a euro fuel distributor.

 

First, you need to understand how the injector works:


From: http://www.auto-solve.com/mech_inj.htm

The injectors fitted to this system will open at a predetermined pressure and will spray a fine atomised 'mist' of fuel behind the inlet valve, waiting to be drawn in on the induction stroke. The fuel is delivered into the engine in a continuous spray and is not timed or pulsed as on other systems. The opening pressure of the injector is at approximately 3.3 bar at which point fuel is injected into the manifold; when the injector pintle opens this will cause the pressure to drop, subsequently closing the injector, which causes the pressure to rise once again and this will of course open the injector. This pintle vibration is called 'chatter' and helps to atomise the fuel before it's induction.
When the engine is switched off the fuel pressure drops below 3.3 bar and the injector closes forming a fuel tight seal, helping to avoid fuel dripping into the inlet manifold.

The spray pattern should be a conical shape and when clean and working efficiently, should emit a high frequency noise: this is the sound of the pintle 'chatter'.

Here is the issue as I understand it from the Porsche guys. The tubing with a thin wall expands when the injector valve closes and then constricts again when the valve opens. So it basically dampens the opening and closing of the valve and messes up the atomization of the fuel. The thick wall tube doesn't respond to the fluctuations in pressure created by the opening and closing of the injector valve. On the flip side, for all I know, the Porsche fuel lines are much longer than Ferrari. The plastic lines on the Mondial are between 10" and about 15". Not very long. Longer lines with have more damping ability than shorter ones. Maybe it's more of a Porsche issue. Not sure. My car has run fine on the 5/3 so far. (It came with them, so they have been on there for a few years at least). Many other people have used the 5/3 in Ferraris with CIS without issues as well.

Birdman

 

Did anyone ever figure out which line we should/could use for this?

 

We're going to have to use:

The global metrics ref# is an old cohline part number for 6mm OD x 2mm ID line that was discontinued.
ID x WALL x OD -- Ref #
2 x 2 x 6 -- 313 0206

Cohline recommends replacing it with this:

6x14 cohline - 3011 3106-23-DIN 73378-74324 - 6x14 -PA 12HIPHL - This is the 6mm OD x 3.15mm ID that has never been imported into the US. It's the closest available to the OEM 6mm OD x 2mm ID line that I've been able to come up with.

I'm working thru a cohline distributor to bring it in. I have 40 meters on special order, should arrive via air freight any day now. That should handle several full CIS systems. Also, I've designed a pair of tools for pressing the 3x8 injector lines into it. I'll post an update as soon as I receive the Cohline, verify my tools & calculate pricing.

I'm thinking in terms of loaning the tools as I expect them to require 3-4 hours machining time to make. Pretty pricey for something you're likely to only need once.

 

Verell,

You are awesome! I appreciate this, as I'm sure others do as well!

Count me in and I can help pay the cost for the tubing and the machine work if necessary. Just PM me and we can work out the details.

John

 

Verell,

Ditto for me too!!!

Happy New Year!

Mark

 

Count me in on the group buy.

stephen

 

Just got a phone call from the distributor, the Cohline arrived from Germany & was shipped to me via FedEx ground yesterday. Should be here early next week. Should have a price once I get it as I'll then have the import cost + shipping costs.

It will take me some time to make the insertion tool & verify it works.

Also, I need to measure a set of lines & calculate the total length + some extra in case you have a problem.

 

Verell,

Great Man. We are all waiting.

V/r,

Mark

 

Great!!!!!

When you get the price figured Post it an I will paypal you.


Stephen

 

Cohline arrived yesterday.
Ouch: Air freight from Germany was $88!! Was expecting $35 - $45. Which is what stuff that size from the UK has been running.

I'm running with a backlog of orders right now, should have bult an insertion tool & pricing late next week.

 

I've got orders for 3 CIS line kits & am trying to get the kit contents finalized so I can ship them in the next few days.

People seem to want a kit that contains enough of each line size to replace all the nylon lines in their CIS system + some extra for error. I've got the lengths of the 6mm OD & 5mm OD lines worked out.

However, a couple of posts mentioned 8mm OD line. I can't find that size used on my '82 Euro 308 GTS QV, The only line that's about 8mm is the steel braid covered lines used from the fuel pump to the distributor, & the return line from the distributor.

If anyone could help me with the length & location I'd greatly appreciate it.

My suspicion is that it was used for the lines to & from the US K-jet w/lambda system frequency valve, & the fuel pump hard line to the distributor, but I don't have a US car available to look at.

I believe I've got the installation tool's design worked out, but haven't machined one yet. I'm pretty sure that a tool is going to be the only reasonable way to insert the barbs into the 6mm line. I'm also trying to design the tool to be usable with the 5mm line.

I'm not sure if the 8mm line will require a tool.

Updatingly,
Verell

 

Verell, some of the K-jets use the 8mm for supply and return to the fuel distribution block instead of the SS braided line.

 

Thanks Scott,
Was it also used in the run over to the frequency valve?

Anyone know the lengths?

 

I'm waiting for the distributor to get back to me on the price for the 5mm & 8mm OD lines. I'm sorry that I didn't recognise that people wanted a complete kit or I would have ordered them back when.

I'll post kit pricing & ordering instructions to the thread this week.

I'm working on the tool design. I'm thinking that I can use the machined pieces of my 1st tool to make a plastic version that I can crank out fairly quickly. Plan B is to have the tool designed so I can machine it quickly. Wouldn't be hard except that the piece clamping the injector barb has to be exactly inline with the piece clamping the tubing while being tapped or squeeezed off-center.

 

My 1st version of the tool was complete as designed, took about 4 hours to enter in the CAD system, then 12 or 13 hours to machine.
Unfortunately, the pieces that clamp onto the line to hold it just didn't grip tight enough. I had to go back & make them, another 4 hours machining time.

After smoothing all the sharp corners off of the areas that clamp onto the line, I inserted a barb into a piece of 6mm OD x 3.15mm ID Cohline. I'd been told that you have to really tap the barb into the line, but it went in with a very firm push with my thumbs.

I'm still waiting on the distributor for the 5mm & 8mm Cohline. The line arrived yesterday, but no invoice with it so I don't know what it cost yet. Will call Monday to get the cost.