Should my Fiesta fuel cap make a sucking sound when you open it? It was bought second-hand, so I don't know if it did it when it was new. In the old days, I'd assume that the vent tube was blocked; but I've been told that 'they all do that, sir'. If so, what is the vent tube for? I know that it has one, but can't easily find the end. Is it designed to maintain a slightly reduced pressure, rather than have it completely open?
In message , Sgt. Pinback writes
My Mondeo does that sometimes, Sergeant.
They all do that sir. Or should.
To minimise the escape of unburned hydrocarbons into the atmosphere, petrol tanks are no longer just open-vented. There will be some type of storage canister, usually carbon-packed, that the tank will vent into. These vapours will be released by a solenoid under ECU control, and burnt by the engine at appropriate times.
The amount of "hiss" you get when you remove the filler cap will be dependent on exactly where in the process the system was when you stop to fill up.
Chris
Thanks for the replies, chaps - I'll ignore it, then.
Thanks for the replies, chaps - I'll ignore it, then.
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