[928uk] S4, GT and GTS engine U-bend fuel hoses

[Martin Dunks]

With regard to real braided hoses rather than braided rubber cheap
lookalike stuff, if anybody wanted to keep the U look, they are made from
stainless steel,  so won't rust & will be 100% compatible with
ethanol/methanol as they are Teflon lined, not rubber.
A suitable heat shrink wrap added would solve any unwanted braided look.


On Tue, 14 Feb 2023, 4:08 pm Jonathan Rackowe via 928uk, <
928uk at lists.928.org.uk> wrote:

> Many of you will be aware of the notoriety of the U-bend fuel hose at the
> rear of the 32V engine in 928 S4 and GTS cars, a hose which has been
> reported to cause engine fires if it fails.
>
>
>
> As my 928 GT is now over 30 years old, and we all know that rubber hoses
> deteriorate with age, I have been keen to replace this fuel hose for some
> time, but unfortunately the part is NLA (No Longer Available) from Porsche.
> There have been replacement parts available from suppliers in the USA, and
> originally I considered buying one of those, but investigating further I
> found that they are either very expensive, having been developed for
> racecar
> applications, or are fairly low quality. I wanted a hose that met DIN73379
> type 3E for 100% compatibility with biofuels so that it would be
> futureproof, and I didn’t want a steel braid on it which would rust and
> prevent me from inspecting the rubber hose. I noted also that parts from
> the
> USA attract import fees and VAT making them even more costly.
>
>
>
> The original Porsche 928 hoses were made by German hose manufacturer
> Cohline, so I decided to work with a UK supplier of Cohline parts to
> develop
> a high quality replacement hose that I would be happy to put on my own 928
> GT. I’m pleased to say that I now have the resulting hose fitted to my 928
> GT. The cost was just £35 delivered and if anyone is interested in seeing
> pictures or obtaining this Cohline hose for their own car please send me an
> email.
>
>
>
> For those interested in the issues developing this part, the biggest
> problem
> with the original U-bend fuel hose is the U-bend itself. With just 80mm
> approx between the Fuel Pressure Regulator (FPR) and the rear fuel damper,
> the U-bend is really sharp and results in a bend radius that is less than
> the minimum specified by Cohline for suitable hoses. The possibilities of
> 90
> degree end fittings and smaller diameter hoses with lower minimum bend
> radius were discussed, but dismissed because restriction of fuel flow would
> be undesirable. Similarly, a straight hose or even a solid fuel line,
> between the FPR and damper was investigated, but the two connections at FPR
> and damper are nothing like aligned, and it would be necessary to loosen a
> fuel rail and the FPR or damper just to fit the hose. The solution we have
> come up with is a 360 degree loop with sufficient hose length to satisfy
> the
> minimum bend radius specified by Cohline. The part is made with latest spec
> DIN73379 type 3E rubber hose and Cohline end fittings with professionally
> crimped sleeves. I’m selling these new fuel hoses on ebay for £38, but
> happy
> to supply them for £35 delivered (in the UK) to anyone on the 928UK list
> that wants one.
>
>
>
> BTW, the short fuel hose at the front of the engine between the fuel rail
> and front fuel damper is still available from Porsche, but inevitably they
> will run out of those someday, so if you haven’t yet replaced that one I’d
> suggest buying one from Porsche while you still can.
>
> Best regards,
>
> Jonathan
>
>
> 928 GT 1991 Amethyst Metallic
>
>