Petrol Smell

[DC]

Re the previous thread about Aero filler cap.

 

I've just finished building my car and I've got a problem with petrol smell. Left hand corners with a tank even half full will produce fumes. Last weekend I fitted an Aero filler cap, looks great but didn't get rid of the problem. My overflow doesn't vent to atmosphere, it's connected to a hose going back via transmission tunnel to the engine. I can't see any evidence of any leakage.

 

Previous car had no problem, even with a full tank.

 

Any suggestions would be gratefully received.

 

Dave C

WEL653

 

 

[Graham Perry]

Are you sure its not coming from the engine bay ? Carb fed cars sometimes throw a small amount of fuel about in left handers, but if set up properly shouldn't do so.

[DC]

I can't handle the power of a Vauxhall. Mine is a Rover 1800cc SS. I've checked the filler neck, and made sure that all clips are tight, and there seems to be no leakage from the Aero cap.

 

Dave C

WEL653

[Peter Carmichael]

Everything forward of the fuel tank is a sealed system, apart from where the fuel comes out of the injectors. A fuel injection system runs the pump constantly and provides an oversupply of fuel to the fuel rail at high pressure (~3 bar). The fuel pressure regulator sends the oversupply of fuel back to the tank. The fuel pressure regulator return line is usually fed into the baffled area surrounding the pump pickup.

 

As the fuel level lowers, air at atmospheric pressure needs to fill the space in the tank, so there is always some venting of the tank, whether valved or via a charcoal canister or in Caterham's practice with Supersports, via an open hose(eek).

 

The hose in question is connected to the filler neck and usually disappears down through the hole in the boot floor to a point just to the side of the fuel tank. In left hand corners, the fuel sloshes up into the filler neck and pisses out of this hose. Fumes are not the problem - litres of liquid fuel gushing out of the back of your car are a considerable problem.

 

The established practice is to replace this with a longer hose and route it in a loop up the rollover bar and then back down to the same position. Mine has been like this for three years. You can also get valves that, while normally open will close when faced with a surge of fluid - usually used to prevent fuel escaping in a rollover incident.

 

Have a really good look again at all the hoses leading from the filler neck. Others have had small leaks from the fuel pump mounting on the right hand end of the fuel tank and the fixings there may need tightening.

[CHRIS CLARK]

Caterham gave me (FOC!)the inline vent valve which allows fumes/air to pass through, but stops the great globs of fuel passing out! They thought it was that that may have been causing the fuel smell from my 1400SS. It turned out to be a series of micro holes in the tank where the unit sits on the chassis 'shelf'!

 

Result of Caterham rebuilding the car after a shunt and not putting any foam strip etc between steel shelf and ali tank!!!!!!