DIY fuel injection lines

[r00b]

I got a roll of nylon tubing to replace the fuel lines at the tank. I've been thinking we could also make the fuel injection lines ourselves for a fraction of the price the vendor's charge. I would use rubber or vinyl house to cover the nylon to help protect it. Has anyone here done this? would I need hose clamps on the barb or is the nylon strong enough to hold at fuel line pressures once it's been pressed on?

[Parzival]

Cheaper maybe, but the fuel injection lines are only $225 and you're getting stainless steel braided lines.
I say go for it if you wanna go through the exercise, but I'll take the SS ones.

[dn010]

I've been thinking we could also make the fuel injection lines ourselves for a fraction of the price the vendor's charge.

I do a lot of my own stuff but this is one area I wouldn't mess around with DIY. I know they're expensive but I'd spend the money on lines from a vendor, that have been designed, built and tested for this purpose.

[Chris 16409]

Buy a set of Ed Udings. They are like $165

https://www.deloreango.com/us/black-stainless-braided-fuel-lines.html

[Kevin 02530]

If you can afford the car you can afford the lines. Honestly probably one of the most important updates you can do. Why cut corners?


Sent from my iPhone using Tapatalk

[FABombjoy]

My chief concern is how exposed they are in the engine compartment to heat and physical stresses during mechanical service. I caught myself on more than one occasion accidentally leaning on or levering against Kjet parts.

The working PSI of nylon tube is sufficient but that will drop at the connection to the fittings. I would only feel comfortable installing something like that as a system with certified ratings.

At the pump? That seems to be OK. Much less heat up there, fewer failure points, covered and protected from abrasion. I'm running nylon there myself and there are a few others, too. For me it's only up to about 50-55psi -vs- Kjet but at least one other owner is running nylon with an external check valve.

[r00b]

More interested in facts and not feelings. If it is a viable alternative, I'll do it. If it's dangerous, I'll buy the lines. I really don't know enough about it yet.




My chief concern is how exposed they are in the engine compartment to heat and physical stresses during mechanical service.

This is also a concern of mine, I may have to do some testing.

[FABombjoy]

Here's my data. Some from experience, some from datasheets, and some feelings whether you want 'em or not ;)

Right now I have 3 different types of 3/8 hoses on-hand and some leftover OEM fuel distributor hose which is likely a smaller diameter. Maybe 1/4 or the metric equiv?

OEM: PTFE w/ outer rubber sheath
-Flexible, clearly high endurance, no issues with permeability. This stuff is probably better than credit given but years of wear and tear may take their toll.


Eaton PTFE w/ braided sheath -6AN (3/8) (Aeroquip FCC06xx), for use with reusable fittings
-Super strong. Ethanol rated, no permeability. Not as flexible as OEM but surprisingly flexible given the outer braid and larger OD. Requires specific expensive fittings.
-2,500 psi / 450 F
I've built 2 EFI systems using the matching Eaton steel fittings to connect the engine to the filter/return. Reusable fittings are likely too large for anything attached to the fuel dist.
This (or similar) hose using crimped-on connectors would be an upgrade from stock which is maybe what the vendors sell?
I don't think any vendor specifies the inner core material but I suspect it's PTFE.
Maybe they don't want to say PTFE due to the orange hoses of death being sold long ago.


Jegs/Summit/Etc "fuel rated, sort by: cheapest first" -6AN braided rubber hose
-There is NFW that I'd put this on anything carrying fuel or oil. Sounds good on paper but other members had issues with this stuff turning into garden soaker hose. Maybe if I needed a coolant line in a pinch. May be too thick to use on the fuel dist even in smaller diameters.


Dorman / Ford 3/8" Nylon tubing:
-Super cheap, easy to cut, easy to install fittings once you get the knack of it and build a fixture to hold the tube. Ethanol rated, no permeability.
-Hard to find real high temp ratings. A similar product at Jegs gives 530 PSI at 70 F. Max is 212 F but working pressure at 212 F not specified.

Surprisingly this is probably the least flexible of the 3/8 hoses. Smaller OD should be better. 3/8 installs on recycled original feed and return fittings.
212 F max rating is pretty close to engine operating temperature. On a cruising summer day I'll see manifold air temps 130-140 F at 70mph, so lots of airflow but that giant aluminum intake is a real stovetop. My MATs will be higher due to turbo, but even a short drive on a 50 degree day sees 100+ with gentle cruising. That's the coolant more than anything else.

[r00b]

Thanks for the info, I was planning on having rubber or vinyl tubing over the nylon line to protect it from abrasion but it might also be needed to protected it from making contact with the hot intake manifold. I hypothesize that the fuel will keep the nylon and fittings at a cooler temperature than the rest of the engine bay.

Anyone happen to know the fuel temperature at the injectors?

[Bitsyncmaster]

Thanks for the info, I was planning on having rubber or vinyl tubing over the nylon line to protect it from abrasion but it might also be needed to protected it from making contact with the hot intake manifold. I hypothesize that the fuel will keep the nylon and fittings at a cooler temperature than the rest of the engine bay.

Anyone happen to know the fuel temperature at the injectors?

My old fuel pump would start buzzing when the fuel hit 125 deg./F

[DMC-81]

Thanks for the info, I was planning on having rubber or vinyl tubing over the nylon line to protect it from abrasion but it might also be needed to protected it from making contact with the hot intake manifold. I hypothesize that the fuel will keep the nylon and fittings at a cooler temperature than the rest of the engine bay.

Anyone happen to know the fuel temperature at the injectors?

The engine temperatures in that area are hot enough to burn your hand.

I feel obliged to chime in on feelings/opinions.... these are not parts to experiment with and hypothesize about. The pressures are high, and the temperatures are hot as mentioned. There are 2 fittings per hose to worry about securing properly. I think the chance of failure is high. So, in those aspects, it is dangerous.

I would perhaps call my insurance company and ask them if they will cover these DIY parts against engine fire.

I am a pretty handy guy, but I would not even think about making them myself, knowing that there are quality offerings from several vendors at a reasonable price point.

[dn010]

+1! Well stated.

[Ron]

+2

...and the insurance company will say, "No"

[r00b]

The OEM lines are rubber over polyamide (AKA nylon) core, that's in my car now! There's already a kit for k-jet lines for a ferrari, it's $70!
It would have been nice to learn what the vendors know, but I imagine there's a conflict of interest :burnout:. Maybe they should get into selling fuel lines to owners of other k-jet cars as well; ferraris, porsches, bmws, volvos.


K-jetronic Products start on page 23
http://www.unobtainiumsupply.com/UnobtainiumSupply_Product_List.PDF

Instructions
http://www.unobtaniumsupply.com/Downloads/Instructions/CIS%20Barb%20Insertion%20Tool%20Instructions.pdf

This thread has some good information
http://dmctalk.org/showthread.php?8492-Light-fuel-leak-at-the-fuel-distributor

A thread about the kit
https://www.ferrarichat.com/forum/threads/unobtainium-supplies-k-jetronic-cis-plastic-fuel-line-hose-restoration-kit.186689/

If you only want the vendor lines, that's fine. I hope they don't destroy your fuel system 10 years down the road.

Does anyone sell OEM style lines?

[DMC-81]

The OEM lines are rubber over polyamide (AKA nylon) core, that's in my car now! There's already a kit for k-jet lines for a ferrari, it's $70!
It would have been nice to learn what the vendors know, but I imagine there's a conflict of interest :burnout:. Maybe they should get into selling fuel lines to owners of other k-jet cars as well; ferraris, porsches, bmws, volvos.


K-jetronic Products start on page 23
http://www.unobtainiumsupply.com/UnobtainiumSupply_Product_List.PDF

Instructions
http://www.unobtaniumsupply.com/Downloads/Instructions/CIS%20Barb%20Insertion%20Tool%20Instructions.pdf

This thread has some good information
http://dmctalk.org/showthread.php?8492-Light-fuel-leak-at-the-fuel-distributor

A thread about the kit
https://www.ferrarichat.com/forum/threads/unobtainium-supplies-k-jetronic-cis-plastic-fuel-line-hose-restoration-kit.186689/

If you only want the vendor lines, that's fine. I hope they don't destroy your fuel system 10 years down the road.

Does anyone sell OEM style lines?


Hey, thanks for your concern. After buying, inspecting, and installing all 13 lines from 2 different vendors, I think I'm comfortable that their quality will last at least 10 years. What features/construction details about them make you wonder about their longevity?

Luckily we don't have to buy these from an unobtainium website. I'm still amazed that we have multiple vendors worldwide that offer parts for a 38 year old orphan car of limited production. So, I'm happy to support them.

[Parzival]

The OEM lines are rubber over polyamide (AKA nylon) core, that's in my car now! There's already a kit for k-jet lines for a ferrari, it's $70!
It would have been nice to learn what the vendors know, but I imagine there's a conflict of interest :burnout:. Maybe they should get into selling fuel lines to owners of other k-jet cars as well; ferraris, porsches, bmws, volvos.


K-jetronic Products start on page 23
http://www.unobtainiumsupply.com/UnobtainiumSupply_Product_List.PDF

Instructions
http://www.unobtaniumsupply.com/Downloads/Instructions/CIS%20Barb%20Insertion%20Tool%20Instructions.pdf

This thread has some good information
http://dmctalk.org/showthread.php?8492-Light-fuel-leak-at-the-fuel-distributor

A thread about the kit
https://www.ferrarichat.com/forum/threads/unobtainium-supplies-k-jetronic-cis-plastic-fuel-line-hose-restoration-kit.186689/

If you only want the vendor lines, that's fine. I hope they don't destroy your fuel system 10 years down the road.

Does anyone sell OEM style lines?

Looks like with the link you provided. That you would need two kits to do all the lines. Thats almost 200 bucks right there. Then you have to make all the connections 2 per line, totaling in at 26 connections, and then hope that none leak.

possible?.. Yes.

Will it really save you any money?.. Not enough that it makes any since, if any at all.

I'm not gonna say not to try it. I just don't see the reason. The lines just don't cost that much money.

[David T]

If you try to do it yourself (DIY) you will not be buying in any quantity that will get you any savings compared to a vendor that WILL buy in quantity to get the price break. Not having experience installing the fittings you will damage some of your stock before you get it right. Then there is the question of if you really did do it right or will a hose pop off? Like brake lines, do you really need to save money that bad? If you feel that the lines must be replaced it makes no sense to DIY it and put lines on that may be even less safe than what you already have on.

[dn010]

Don't forget the cost of the tooling to crimp the fittings on unless you're going to buy barbed banjo fittings. I don't know - maybe it's just me, but I'm sure there is a good reason no one has ever tried doing this before.

[r00b]

Hey, thanks for your concern. After buying, inspecting, and installing all 13 lines from 2 different vendors, I think I'm comfortable that their quality will last at least 10 years. What features/construction details about them make you wonder about their longevity?

I read about some orange lines that were often used for the tank lines. It turned out their life was 10 years and the lines would deteriorate internally blocking the fuel filter. When used after the filter they would destroy the fuel distributor. Though stock fuel lines do age well, they are long past their designed life and need to be replaced. Whatever the case, in the short term, they are better than the 38 year old lines in some cars. If the material is better than nylon I want to know about it.


I'm still amazed that we have multiple vendors worldwide that offer parts for a 38 year old orphan car of limited production. So, I'm happy to support them.

I'm also happy to support the vendors when they make new parts unique to the car, not so much so when it's the exact part I cat get at autozone or on amazon for 1/3 the price. It is nice that they do offer those parts, if you don't want to figure it out yourself.


Looks like with the link you provided. That you would need two kits to do all the lines. Thats almost 200 bucks right there. Then you have to make all the connections 2 per line, totaling in at 26 connections, and then hope that none leak.


I think the most important part is knowing that it will work and what sizes to get. If you install the nylon correctly onto the barb it won't leak.


If you feel that the lines must be replaced it makes no sense to DIY it and put lines on that may be even less safe than what you already have on.

There isn't some complex process to installing nylon tubing onto barb fittings. That's what the car came with, why would it be less safe. Certainly not less safe then 38 year old lines.

I was hoping to get more input from people who know far more than me on the subject, facts on why it would or would not be a good idea. In the past this would have happened, maybe times have changed. I don't care about the opinions of naysayers who say you can't because they can't and tell you not to even try. I'll see if I can get my hands on the correct sized tubing, if not I'll just get the lines from the vendors. If no one is interested in alternatives I'll keep my future projects off the forum.


Don't forget the cost of the tooling to crimp the fittings on unless you're going to buy barbed banjo fittings. I don't know - maybe it's just me, but I'm sure there is a good reason no one has ever tried doing this before.

I found in my research that people use a tool for making flare fittings to hold the nylon so you don't have to buy the expensive tool. I believe all the stock fittings are barbed banjo since the car came with nylon from the factory and I have the factory lines, I'm not sure about the return line, it looks like some white plastic or nylon is in there where the hose joins. Turns out people have done it before for their k-jet ferraris.

Really I want to know what the new lines are made of so I can go down that rabbit hole of research.

[DMC-81]

I read about some orange lines that were often used for the tank lines. It turned out their life was 10 years and the lines would deteriorate internally blocking the fuel filter. When used after the filter they would destroy the fuel distributor. Though stock fuel lines do age well, they are long past their designed life and need to be replaced. Whatever the case, in the short term, they are better than the 38 year old lines in some cars. If the material is better than nylon I want to know about it.


I'm also happy to support the vendors when they make new parts unique to the car, not so much so when it's the exact part I cat get at autozone or on amazon for 1/3 the price. It is nice that they do offer those parts, if you don't want to figure it out yourself.


I was hoping to get more input from people who know far more than me on the subject, facts on why it would or would not be a good idea. In the past this would have happened, maybe times have changed. I don't care about the opinions of naysayers who say you can't because they can't and tell you not to even try. I'll see if I can get my hands on the correct sized tubing, if not I'll just get the lines from the vendors. If no one is interested in alternatives I'll keep my future projects off the forum.


Really I want to know what the new lines are made of so I can go down that rabbit hole of research.

I know that under the outermost black PVC coating, and under the next stainless steel braided layer, they appear to have a whitish nylon type hose. No orange hose, but I don't know exactly the type of material. I like that they have 3 layers. The lines that I got from DeLoreanGo are described as "Very high quality item made in the UK. Manufacturer's lifetime warranty. DOT, ADR and TÜV certified." Perhaps you can research what fuel line material(s) meet those 3 government standards? My lines from DMCH are very similar looking.

Also, from a mechanical empathy perspective, I have chosen to use non-ethanol fuel in the DeLorean, and I applied thermal shielding on lines near very hot surfaces....just for added peace of mind.

I am all for figuring it out myself as this example thread from my restoration shows, but I don't think it's worth the risk on these parts:

http://dmctalk.org/showthread.php?15632-Refurbing-a-Very-Early-A-C-System

My opinion is you are overthinking it. We laid out several reasons to not DIY, but at the end of the day, it is your car.

[David T]

It is a lot more than just cutting a hose to length and shoving a barbed fitting into a hose. If you don't get the exact correct fitting to use on that specific kind of hose the connection is of very dubious value. Some hose and fittings require a specific tool to hold everything just so to make a proper connection. There is a science to this. If you are really serious about this find a local hose shop like an Aeroquip dealer and get the right stuff. Shops like that will make the hoses up for you so you KNOW it is assembled with the right hose and fittings and done properly. Do that and then compare what it cost to what the vendor's kits cost. I am betting the vendor's kits are a better deal.

[DMCMW Dave]

Something else to think about with respect to the comparison between the fuel pump/line hoses and the injector hoses. In the main fuel lines, the fuel flow is pretty significant, on the order of a gallon every few minutes since the system is recirculating. This holds the temperature of the hoses near the tank at not much over 120 degrees. (I'm sure Dave M has measured it but I don't recall the number!).

OTOH, the fuel in the individual injector lines is moving very slowly, i.e. only at the rate of consumption of each injector. So not so much cooling effect, therefore the temperature of the fuel in those lines, and the lines themselves, approaches the temperature right on top of the engine. This makes the composition of those lines even more important than the lines at the tank.

[Parzival]

you know what would be interesting to see?
Has any one even routed the hard metal style injector lines that are sometimes used on K-jet systems?

[r00b]

you know what would be interesting to see?
Has any one even routed the hard metal style injector lines that are sometimes used on K-jet systems?

I was thinking about that too.

[r00b]

Something else to think about with respect to the comparison between the fuel pump/line hoses and the injector hoses. In the main fuel lines, the fuel flow is pretty significant, on the order of a gallon every few minutes since the system is recirculating. This holds the temperature of the hoses near the tank at not much over 120 degrees. (I'm sure Dave M has measured it but I don't recall the number!).

I've been planning to install this, to cool returning fuel, in a duct bringing in cool air from in front of the radiator.
60054

[Bitsyncmaster]

Something else to think about with respect to the comparison between the fuel pump/line hoses and the injector hoses. In the main fuel lines, the fuel flow is pretty significant, on the order of a gallon every few minutes since the system is recirculating. This holds the temperature of the hoses near the tank at not much over 120 degrees. (I'm sure Dave M has measured it but I don't recall the number!).

OTOH, the fuel in the individual injector lines is moving very slowly, i.e. only at the rate of consumption of each injector. So not so much cooling effect, therefore the temperature of the fuel in those lines, and the lines themselves, approaches the temperature right on top of the engine. This makes the composition of those lines even more important than the lines at the tank.

I did measure with two therm o-couples the fuel temp leaving the tank and fuel temp returned to the tank. It was about 1 deg.F warmer on the return temps. So I concluded that most of the fuel heating was due to the returned fuel. I did have the hot air dam on my car and the tank temps would easily get to 125 deg.F and then my fuel pump would start making noise. I installed a fuel cooler on that return line and never heard the pump noise again.

[r00b]

I did measure with two therm o-couples the fuel temp leaving the tank and fuel temp returned to the tank. It was about 1 deg.F warmer on the return temps. So I concluded that most of the fuel heating was due to the returned fuel. I did have the hot air dam on my car and the tank temps would easily get to 125 deg.F and then my fuel pump would start making noise. I installed a fuel cooler on that return line and never heard the pump noise again.

I remember seeing a picture of you cooler, what was the temperature after you installed it?

[Bitsyncmaster]

I remember seeing a picture of you cooler, what was the temperature after you installed it?

I never measured the temps after the install. You really need to to driving for the AC to work best (my AC accumulator cooled the return fuel). Since it cured my buzzing pump problem I was happy without further testing.