Fuel smell, breather pipes look ok

[red vtec]

I have read all the posts on fuel smell concerning breather pipes, I have checked mine and they appear to be in very good condition, in fact I think they have been replaced.

My fuel smell is worst when the car has just been filled, anyone any ideas? Would this indicate that it is a fuel tank issue? My tanks look like they are replacement alloy ones, so I'm a bit confused,

Thanks

Chris

[troutrou]

The breather pipe (around the rear screen) has been replaced, but what about the balancing pipe connecting the bottom of the tanks ? Maybe this one is still original ?

[Sparky]

Top tip from Trev that solved mine - check your filler cap rubbers! Mine were so brittle that I could snap them in half. Replaced them (cut from an appropriate rubber sheet) and smell gone.

[red vtec]

Thanks for the replies, I had thought about the balancer pipe, guess I need to get under the car and have a look.

Sparky where did you get the rubber sheet?

Thanks

Chris

[Jonathan]

Mine has this - GT3, terrible fuel smell yet when I pressure tested it and blocked the breather everything was tight and held pressure.

Any clues, still wiffs like crazy but only in the engine bay, even when standing, no sign of fuel leaks either

[red vtec]

Hi Jonathan,

I think the first step for me will be to replace the seals as Sparky has done, and then take it from there.

Chris

[Choppa]

Chris,changed my filler cap seals a couple of weeks ago PNM had both G and Stevens types in stock .

Edited August 10, 2010 by Choppa

[Jonathan]

They're not leaking though, holds perfect pressure when the vent is closed up, the smell is also inside the car not outside.

[Bibs]

What's the difference in molecular size of air and fuel vapour? Helium balloons leak and air filled ones don't due to this, your tanks could be air tight but not fuel vapour tight.

[slewthy]

You would imagine that a hydrocarbon would be larger than most components of air.

What we need is a molecular scientist.

[Jonathan]

I doubt that is causing the nasty niff in the engine bay...

I did check all the seals, swapped them with the GT2 as well, checked the filler cap (only 1 on the GT3) and the hoses - if there is no air leaking past under pressure then there wouldn't be anything sufficient to woft the fumes out and about - if petrol fumes seeped past the rubbers in this amount of quanity then all cars would smell like this.

Leak tests couldn't find any cracks etc in the pipework or the tanks, I guess it could be the engine crank breather ?

[lotus4s]

Could be a leaky injector or fuel pressure regulator. I've seen both leak. I don't think you'd get raw fuel smell from the crankcase breather.

[superdavelotus]

Jonathan,

Check the O ring on your fuel rail. There's an article here http://homepages.ipact.nl/~theunissen/

I think it's either the balancing pipe or fuel tanks. Balancing pipes can become porous too!

David

[wookiecj]

if there is no air leaking past under pressure then there wouldn't be anything sufficient to woft the fumes out and about - if petrol fumes seeped past the rubbers in this amount of quanity then all cars would smell like this.

Fact:- Hydrogen Sulphide can be detected by humans in a concentration of 1 part per million H₂S to Air whereas at 100-150 ppm it deadens the sense of smell.

I don't know the detection concentration for fuel vapour/hydrocarbons but it may be a similarly small figure and can't be easily discounted.

If you've done all the breather pipes above the engine between the tanks (don't forget there is an NRV in some cars) then it's time to do the filler cap rubbers. It may not seem entirely logical but it has been shown to work in the past.

We've just finished a car where the breather pipes, on initial inspection, seemed fine but were in fact perished at one of the connections/junctions (there were 7 in all) and at two of the bends, one of which was masked by glue/sealing stuff so it pays to be extra careful when examining the integrity of the pipes.

Let us know how you get on.

Edited August 11, 2010 by wookie

[red vtec]

Sparky,

just checking the replacement is the actual rubbers on the fuel filler caps NOT the body Gasket clamp ring where the neck goes through?

Ta

Chris

[Sparky]

Hi mate. Clearly check both, but I suspect you'll find the filler cap rubbers really brittle and porous. That's first on the agenda.