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Replacing 928 Fuel Lines - a guide

 
Old 04-20-2015, 11:13 PM
  #61  
Preston2207
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ok good info. Here's some hypotheticals..

Would you if you where stuck somewhere or say had to have a drive, and you had these hoses in the back or say garage, use them for a short term. Or something to that matter (Couldn't hurt to have a roll of the hose and some clamps right?)

Would you take a hose off the car and take it to a local hose mfg. and have them rebuild it with their hose. And use/trust these hoses for "permanent"

Or three.. Only recommend porsche fuel hose?
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Old 04-20-2015, 11:26 PM
  #62  
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odds are if your current hose were to fail the subsequent fire makes it a moot point. That said I did have an injector hose fail on a 914 pumped 1/8 of a tank on the engine with no fire....how it did not ignite at 70 mph on the freeway is still a mystery to me.
I used Greg Brown's fabricated hoses as the Porsche ones were NLA / discontinued.
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Old 04-20-2015, 11:33 PM
  #63  
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Originally Posted by Preston2207 View Post
But isn't that what this thread is about? One particular part on the 928? The fuel lines? No one is arguing the entire engineered genius of the porsche... Just maybe a few unintelligent designs. And as probably the newest member of this forum I'm kind of confused with this thread. Should we or should we not use Carl's hoses... Bottom line all BS aside- Will. It. Work?



Will it work? Most likely.


So I had a mild whiplash injury from a pretty hard fall while skiing about 40 years ago.. Ended up seeing a neuro who discussed surgical options. Success rate? 97%+. Failure mode? Partial to complete paralysis. This is along the same lines -- 97%+ will never have a problem, particularly if they don't tighten the clamps hard enough to fracture the inner rubber lining. Failure mode? Strats with a little fuel fragrance if you are lucky enough to catch it in time. What do we do with clamped hoses that have a little seepage? What was the next failure mode?

So long as you are aware of the risks, the costs and the failure modes, do whatever spins your prop. If the car burns in the garage and the house (or worse) goes too, what will you say to your insurance carrier beyond 'Oooops!'?

As I shared above, I get to visit some interesting large gas turbine engine "problems". There are experts at the metallurgy and the mechanical failure modes. I usually deal with the external stuff and the human factors that contribute to failure. Reality is that virtually all non component failures have been documented extensively, and that stuff is shared within the industry. So when someone proposes a nifty cost- and/or time-saving shortcut, the first step is to research previous failures related to a similar shortcut. Sometimes, even with that information in hand, someone decides that this time it will be different. I advise them to call their insurance carrier and get a written OK for what they propose. I already know what mine will say if I do it.

Remember that engineering is the science/art of not making the same mistake again. That includes learning from the mistakes of others, since "same mistake again" doesn't differentiate who made that mistake last time.

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Old 04-20-2015, 11:47 PM
  #64  
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Originally Posted by Preston2207 View Post
ok good info. Here's some hypotheticals..

Would you if you where stuck somewhere or say had to have a drive, and you had these hoses in the back or say garage, use them for a short term. Or something to that matter (Couldn't hurt to have a roll of the hose and some clamps right?)

Would you take a hose off the car and take it to a local hose mfg. and have them rebuild it with their hose. And use/trust these hoses for "permanent"

Or three.. Only recommend porsche fuel hose?
Doesn't have to be Porsche fuel hose. The only discussion point is about using the correct hose for the duty and the fittings. Or, how lucky do you feel?

I've seen some pretty crazy temporary, "just-enough-to-get-by" fixes on cars. 928's are great examples, where the purchase price of a used one is just a small down payment on total ownership costs. Save a little here, cut a corner, scrimp on things, substitute a cheaper aftermarket workaround part until you can affort the right part. I don't want to fix the leaks in my AC system, isn't there something I can put in just to make it through the summer?

Part of a good PPI is making a list of all the stuff on a candidate car that will need attention to make it "right". My definition of "right" is sometimes vastly different from what others consider "right". Or they may confuse "right" with "OK" and "that will get me by until I can afford to do a real repair". I throw a basic $5k number out for replacing rubber bits and critical wear items, assuming the car hasn't been short-cutted or otherwise abused too much. Maybe this is the contributing factor to why thses cars have such a reputation as money pits. They aren't if you do things right the first time. Like put the right parst in when you do a repair. How much more expensive do you think the Cohline hose is compared to parts store FI hose with clamps? If you factor in anything reasonable for your labor, any difference in the hose cost fades into the noise. Why not just buy and install the right replacement stuff to begin with? If I do, I'll dodge the "what would you do if it was..." questions completely, at least for the next 25+ years.
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Old 04-20-2015, 11:59 PM
  #65  
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I am sure that I am opening a whole can of worms here, but I am genuinely curious about the answer to the whole fuel line issue, assuming such a thing does exist.

I have an 84 L-Jet, and I had to replace a couple of leaking injectors so I also replaced all of the little hoses that go from the rail to the injector while I was in there. Everywhere that I read, it was said that the correct hose to use was N-020-281-1. This is a 7 mm hose and it does NOT have an inner plastic veneer. This is the hose that Greg Brown recommends, and apparently Roger recently ordered an injector hose repair kit straight from Porsche and this is the hose that he received, along with both clamps and hats.

Here is where I am genuinely confused, and I swear to god I am not trying to stir anything up, but I'm just genuinely curious. Why is it okay to put these hoses with clamps (tightened to the appropriate degree) on barbed fittings on the injectors but it's absolutely a non starter to put them elsewhere in the engine bay? Sometimes the same people are the ones giving these seemingly contradictory pieces of advice.

I know that someone might justify it by saying that these little injector hoses are "captive" and can't be blown out of position because they are being held in from both ends, but I don't see how any of these hoses could blow off unless you use a hose that's way too big. To the contrary, when I had to take my injector hoses off (they were EFI hoses with clamps) I had to cut them as they were impossible to just pull off. These hoses swell and seem to seal very well.

If I am missing something I would genuinely love to know, as I am fully aware that I am the last person to claim to be an expert on any of this. I really want to keep my car from burning down, but I don't understand why rubber hose and clamps are fine for the barbed injectors and fuel rails but not for the other barbed fuel lines right next to them.

Again, not calling into question anyone's judgement or expertise, but I am confused and would like to know the reason for the seeming contradiction. I didn't ask this question earlier because I didn't want to start a flame war on the issue (no pun intended), but since we're having this discussion I guess now's as good a time as any to ask.
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Old 04-21-2015, 01:17 AM
  #66  
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Originally Posted by Simon928 View Post
Here is where I am genuinely confused, and I swear to god I am not trying to stir anything up, but I'm just genuinely curious. Why is it okay to put these hoses with clamps (tightened to the appropriate degree) on barbed fittings on the injectors but it's absolutely a non starter to put them elsewhere in the engine bay? Sometimes the same people are the ones giving these seemingly contradictory pieces of advice.

Again, not calling into question anyone's judgement or expertise, but I am confused and would like to know the reason for the seeming contradiction. I didn't ask this question earlier because I didn't want to start a flame war on the issue (no pun intended), but since we're having this discussion I guess now's as good a time as any to ask.
The difference is the shape of the barbs and where the clamp rides.

The barbs on the fuel fittings are sharp (see earlier pictures in this thread), and when clamped down upon, may damage the inside of the fuel line. The sharper barbs are specifically for use with polyamide (nylon) fuel hose, which is a plastic rather than soft rubber. The only rubber on the original hoses is the cosmetic/protective outer sheath.

The coolant hoses etc. which have a raised "barb" aren't at all sharp and don't cut the rubber hose over them, plus you don't actually clamp on top of the barb.

Here's the fuel barbs:


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Old 04-21-2015, 10:15 AM
  #67  
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Thanks for the reply Hilton! I'm aware about the differences between the barbed fuel fittings and the fittings for coolant lines etc. Why I'm scratching my head is because sometimes the same people say to put N-020-281-1 rubber hose (no inner plastic veneer) between the fuel rails and the injectors, and that area uses the same barbed fittings as you pictured. If it's okay for that application, why is it a non-starter for the other barbed fuel fittings?
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Old 04-21-2015, 02:53 PM
  #68  
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Simon - we are mixing theory with practice. In theory you should never use an EFI hose on a barbed fitting - in practice can you and will it work - yes and maybe. Is it the right thing to do - NO!!.
I used to sell the EFI hose and clamps and extolled the virtues of its use. I have since come to understand that it is not the correct way of doing the job. Add to that the different owners of our cars and there ability/none ability to do the job correctly and check the hoses and clamps on a regular basis.
Couple that with liability insurance and that in my case my company is a Corporation with the added responsibility that brings.

For once I agree with Carl and suggest potential users read the information given and make there own choice on what to use and accept the liability for doing so.
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Old 04-21-2015, 03:30 PM
  #69  
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Thanks Roger. If we shouldn't be using the hose on barbed fittings, what do you recommend as the proper way to replace the little injector hoses on my 1984 L-Jet? Everywhere I read said to use N-020-281-1 rubber hose--even Greg said as much in a post that I looked at for research, and I know that he's vehemently against using EFI hose in other settings when barbed fittings are involved.
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Old 04-21-2015, 03:46 PM
  #70  
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I thought I had read (and someone above said similar) that those injector hoses aren't really barbed like the others, more of a smooth bulb and then the clamp goes behind it, not on top of it? But I don't have a 16V car so I may be all wrong about that.
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Old 04-21-2015, 03:49 PM
  #71  
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Originally Posted by bureau13 View Post
I thought I had read (and someone above said similar) that those injector hoses aren't really barbed like the others, more of a smooth bulb and then the clamp goes behind it, not on top of it? But I don't have a 16V car so I may be all wrong about that.
The places to connect the hose on my fuel rails are barbed.
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Old 04-21-2015, 03:55 PM
  #72  
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Default A total mystery

Yeah, I'd like to know too. But I am rapidly coming to the conclusion that no one may know, although since these connections are barbed, rubber house is not ideal.

Here's a picture of the catalog page for my car's injectors. Every other hose (for example, going from the fuel pressure dampeners) is identified by a part number that resolves to the rubber hose. As everyone knows, these connections are not barbed.

However, Number 21, which should be the short hose from the rail to the injector just says "injector valve," meaning the whole assembly -- injector and hose. What I think is that if you bought this part from Porsche back in the day, the hose came attached to it already. So what hose did they use? Who knows. It may even be the rubber hose, since I suspect my car's rubber was never changed (it had the ferrules on it) or was changed by a dealer, and that hose was not plastic lined.

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Old 04-21-2015, 04:09 PM
  #73  
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That's the funny thing that I mentioned in my original long-winded post--you apparently CAN buy these replacement hoses from Porsche. What they give you is N-020-281-1 (rubber hose) with clamps and hats. This hose has no inner plastic veneer, but the original hose apparently did. I just put my injectors back on my car and used that same hose that Porsche (and Greg and a few others) told me to use. But going by what everyone here is saying, this is a fire hazard and should be avoided. So what is the right way to do this? Is there a different hose that is the new consensus choice as the correct hose to use?
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Old 04-21-2015, 04:16 PM
  #74  
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OK, I knew I remembered Greg talking about this. Here is what I dug up from an older thread on this very topic:

"Here's the whole story, in a nutshell:

Never, never, never put a rubber hose with a clamp over barbs that were originally made to have plastic hose over them. Your main feed hose (and possibly the main return hose) are of this construction. The problem with the barbs is that they are very sharp and will cut the inner liner of the hose when a hose clamp is tightened down.

Worth noting, there is a product called "push lock" hose and hose ends, which is sold by several manufacturers. This rubber hose goes over very sharp barbs....but because it was designed to be the perfect size, it does not require a clamp!

The original injectors did not have barbs, but did have a "bulge" to keep the hose from blowing off the end. If a clamp is used, it tightens down on a smooth metal surface, not a sharp barb.

If you have the original "hats" that were on the injectors and the fuel rails, you will not need clamps, if you use the N020 281 1 German hose. Those "hats" kept the end of the hose from cracking and flaring out. If you do not have those "hats", simply use clamps made for fuel injection hose. This style clamp has "turned up" edges, to keep the hose from being cut/damaged."


Originally Posted by Simon928 View Post
That's the funny thing that I mentioned in my original long-winded post--you apparently CAN buy these replacement hoses from Porsche. What they give you is N-020-281-1 (rubber hose) with clamps and hats. This hose has no inner plastic veneer, but the original hose apparently did. I just put my injectors back on my car and used that same hose that Porsche (and Greg and a few others) told me to use. But going by what everyone here is saying, this is a fire hazard and should be avoided. So what is the right way to do this? Is there a different hose that is the new consensus choice as the correct hose to use?
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Old 04-21-2015, 04:28 PM
  #75  
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I was just on the phone with Greg, and he said that the barbs on the fuel rails are somewhat different then the other barbs in the fuel system, so the N-020-281-1 hose is okay. You are supposed to use hats on the top, but if you do use clamps make sure you don't tighten them too much or you run the risk of cutting the hose on the inside against the barbs.
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