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Grizzly

Elite fuel filler pipes Non Return Valves Orientation

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Hello,  

Which way round are the NRVs in the filler neck breather pipe tubes?

My view is that they let air in to the tank as it empties as the tubes they are in are not vents. 

I do not think they are tank vents as our cars are not fitted with the evaporative loss tank and charcoal canister system.

Are they needed at all?

 

Opinions invited

 

Brian

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Upgrade today to remove Google ads and support TLF.

It is important that the tank is able to "breathe" (hence - breather pipe tubes!) if the temperature rises so I think they should go the opposite way to what you have suggested 😉.  I'm just going to run the breather pipes up and over the tank - probably without any NRVs.

Pete

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Hello,

I've done a bit of reading

My Elite Workshop Manual only gives a very short General Description, but does say that "Tank ventilation is via the filler caps on European cars, ............" I've had a look at my filler caps and they do not appear to have ventilation holes in them and fit quite snugly.

The illustration in the Manual only shows the full Evaporative Loss System for Federal Cars - no NRV is shown, or listed

The Service Parts List only shows the Evaporative Loss System but does call off a "NRV Filler Neck Breather, Part no. B076L6001F, for Domestic (and ROW) Elites, but not for Federal cars", and is "Not Illustrated"

I am still of the opinion that, if NRVs are required they are to allow air into the tank as it empties, but will not let petrol fumes out and that "breather" is a generic term for pipes to / from tanks, not just car fuel tanks,  much like Hoover  is used for all vacuum cleaners. 

 

Now how long should the plastic pipe be and where should ir run? - see the other current thread,

 

Brian

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The fuel system parts table on the rdent site lists different fuel caps for federal and domestic markets + has part Ned for the NRV’s

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Hello Rob,

I'm not quite sure what point you are making - perhaps you would clarify

 

Thanks

 

Brian

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The tank ventilation holes in the filler caps are easy to miss - it is a TINY hole in the flange that faces the tank.  I've changed to the vent on the filler neck type as I'll be running an aluminium tank - especially important not to pressurise.

The pipes run from each filler neck up and over to the opposite side of the car and then down to vent to atmosphere - so the nearside filler vents on the offside etc...

Maybe check out tank breather valves on Think Automotive's website - they have an in-line one available.

Pete 

Edited by EXCEL V8
Add info.

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Hi Brian

just that there are different part nrs for federal and domestic filler caps, which match the different systems.

 

br

rob

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Are they absolutely non-return valves and not anti-flow valves for if the car rolls over? I've never seen the Elite's system but the Esprit had valves that would allow air to move either way so long as the valve was near-vertical, if it was tilted too far then  the valve closed and so in the event of a roll-over type of accident, you'd not get massive fuel leaks.

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Can you post a photo of your valve?  Maybe someone has retro-fitted a roll-over valve from another car?  Has your car got the little breather tubes brazed to the filler necks?  I'll take some photos later of the different filler necks (not got time till later today!)

Pete

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OK - on the left is the early Elite filler neck - no vent tube brazed on; the tank vents through a TINY hole in the fuel cap - fuel escapes via the same hole!

On the right is the later filler neck (ignore the extra bit welded to the bottom of it - I did this before deciding to fit a motor-sport tank vent valve); this type vents via this little tube - not sure if a roll-over valve was ever fitted.

The little bit on the right is a roll-over valve from a late (89MY) Excel (I thought I'd still got it!!).  It allows free venting of the tank to avoid pressure build up but completely blocks fuel escape if you're upside down in a ditch.  It is fitted vertically.  It categorically only fits one way - with the short black hose fitting to a barb on the filler neck.  As Grizzly originally said - air has to get into the tank to avoid a vacuum forming as fuel is used, but it is also a vent to prevent pressure build up - it vents to atmosphere.

Pete

RIMG0418.JPG

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Thanks for the photos, Peter.

I have the filler necks with the little breather tubes on the side on both sides of the car

I have a suspicion that the Eclat and Excel system is different from the Elite system due to the number of filling points (one versus two)

I don't think my Elite was fitted with the roll-over valves, these being too new and used mainly in Motorsports where the possibility of a car overturning can be high. 

At nearly 70 years of age I won't be driving anywhere very fast, even if I get the car on the road, and the likely hood of me turning the car over is remote. So, for me these may be overkill

Fuel spill safety valves seem to only work in a vertical position and there is very little headroom above the breather tube connection to fit one, though the one in Peter's photo is very neat.

From an environmental point I would like to prevent petrol fumes escaping from the tank, so a one way valve to let air in is for me

But as the point has been  made you also want to stop pressure building up in the tank. The only way I can think of this happening would be in prolonged hot weather, longer and hotter than we have experienced so far. My tank had painted on the side "Pressure Tested to 0.3 kg/sq cm" which is 5psi - would it see that sort of pressure in this country (plus the factor of safety is unknown)

Enough said - you have to make your own mind up

 

Brian

 

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Hi Grizzly

Fitting a one-way valve that will only let air in will stop petrol fumes getting into the atmosphere but may cause unforeseen safety issues:  If the tank generates enough pressure to overcome the needle valves in the carbs the tank may vent via this route resulting in petrol pouring onto the distributor (lots of sparks!).   Modern valves are available that stay firmly closed until a pre-set pressure is exceeded and then vent briefly to the atmosphere to equalise the pressure.  They are not open all the time like roll-over valves, so you don't end up with fumes in the garage etc..  You could also fit a charcoal canister after the valve to reduce even further the environmental impact of the venting process.

Pete

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A very valid point, though I am considering fitting an in-line pressure regulator before the carbs to  restrict pressure to 3.5psi. A charcoal canister arrangement, at the moment, is not on my list, but it may come to that one day

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why fit a regulator if the pump limits the pressure? I don't think the pump allows freeflow through it, but I haven't tried either. Worth a check?

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Because the Facet fuel pump can deliver fuel at more than 5 psi I believe (I'd need to look it up again) which is too high for the carbs which need 3.5 psi to operate properly. I intend to fit a pressure gauge connection too to see what the actual pressure delivered by the pump is before fitting a regulator. It is all about testing components to understand and design the right system. I wanted to check my pump delivery pressure out before fitting it but do not know anyone with a test rig. So I'll do it when commissioning the engine.

There's a very interesting  design here devised by a Noble owner. Very expensive too - but if you own a Noble.......

https://www.pistonheads.com/gassing/topic.asp?h=0&f=26&t=988527&mid=158155&i=20&nmt=fuel+pump+issue+!!&mid=158155

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Again willing to learn -

" This pump features a uniquely designed restrictor tube to maintain a stable fuel system pressure between 3-4 psi in a return-to-tank system."

What is a return - to - tank system please

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this might help:  https://www.onallcylinders.com/2017/10/10/return-returnless-fuel-system-right-video/

but, my Elite does not have a return line. I have the above fuel pump in, and it works perfectly, starts no problem every time. In theory a return line with pressure bypass may work slightly better. I am relying on the fuel pump regulation, and have not checked pressure, but for all practical purposes, it works. I do know a facet pump will cause issues if not regulated, the needle valves can't cope with the pressure. But the ECCO pump seems fine.

When first turning on ignition, i can hear it ticking, then stops when line pressurised. Just like the SU pump

 

 

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Quote

 

Hi to all,

You can also get an electronic conversion for the original SU pumps, the electronics module replaces the points on the SU unit. I think its by Burlen Ltd if I remember correctly. They make SU carbs.

 

John

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