vacuum in petrol tank

[les.lin]

hi all
problem with vacuum in petrol tank.the purge valve will not stop this is located top of radiator rh side this eventually damages petrol pump connections.
car is 1.8 petrol v40 2002
atb les

[canis]

Is it? I thought it was attached to a carbon canister under the right front wing.

[les.lin]

hi
no located as stated.filter is under wing.what i am trying to find is information on how the uk spec evaporation system works can find nothing.mine is running full time and thus crushing the tank which in turn breaks the wires on the tags on fuel pump.i only have to leave engine running for ten minutes or so and there is a very noticeable hiss on releasing filler cap.
les

[Dippydog]

Must admit I've not given any thought previously to how tanks are vented,I just thought it'd be done as it was previously where there was a tiny hole in the underside of the filler cap or there was a small bore pipe attached high up on the fuel filler pipe[which also served as an overflow pipe]which would allow air into the tank as the fuel was sucked out by the fuel pump.Is this no longer the case?

[canis]

It stands to reason air must be allowed in somehow. But it must not be allowed out again, and that's what the canister does. On mine, right next to the water bottle, it hangs and attached to is is a little valve.

A rise in ambient temperature will cause the tank to want to release pressure, which it does through a third pipe, into the canister. I presume it's full of charcoal, since charcoal has a very large surface area, to collect evaporated petrol, but I haven't actually opened it. The engine can burn the evaporates when idling, decelerating, etc.

If the valve is faulty, you will just have to replace it. Sounds much easier to get access to it on the radiator than where mine is.

[ITSv40]

According to Haynes:

The evaporative emission control system is used to minimise the escape of evaporated fuel into the atmosphere. To do this, the fuel tank filler cap is sealed and a carbon - filled canister is used to collect and store petrol vapours generated in the tank. When the engine is running, the vapours are purged from the canister by means of a vacuum - driven, ECU-controlled solenoid purge valve. the vapours are then passed into the inlet tract to be burned by the engine during normal combustion. To protect the catalyst and to ensure that the engine runs correctly when idling, the purge valve only operates when the engine is running under load. As a safety measure, a roll-over valve is incorporated into the system which closes when the car tilts sideways by more than 45degrees. This prevents fuel leaking in the event of an accident. The carbon canister is located under the left-hand front wheel arch and the purge valve is located in the engine compartment, in front of the inlet manifold.

It appears to me that the OP needs to fit a new purge valve.

[Dippydog]

I for one thank you for those explanations,so that's what the carbon canister is for and how it's meant to function! Everyday's a school day

[ITSv40]

Originally Posted by Dippydog

I for one thank you for those explanations,so that's what the carbon canister is for and how it's meant to function! Everyday's a school day

Yes, indeed. I had never quite got my head around what exactly it did. Sometimes it is a case of 'if it ain't broke, I don't need to know what it does'.

[les.lin]

sorted!!.replaced canister under wing old one saturated water not petrol.15yrs old
not bad i suppose.got one from local breaker new one quoted from local volvo stealer £140 argh .see how long this one lasts

les