No 'Hiss' when removing fuel cap ?

[Newcastle knight]

I got out the car the other week and i got the whiff of petrol, and followed my nose to the fuel filler cap, i opened the door and it was fairly noticeable. I took the actual cap off and it used to give of a nice hiss of pressure, but this time i got nothing. Again took it out for a spin tonight and checked again when i put it back in the garage, but no hiss this time either.

the cap is brand new, i only fitted it last year, it was advertised as a 2nd gen one but John told me it would fit, which it does, it fits mine no problem and locks fine too, im just assuming its not making a good enough seal ?

the car hasnt been running quite right lately so would this have anything to do with that ?

Scott

[SUPERCHARGEDGTA]

could be faulty cap valve (should let air in but stop vapour escaping)
or leaking breather hose (to carbon canister)
neather would affect running. if it was blocked and could not get air in it would but not open as it is

[Newcastle knight]

whats this breather hose to a carbon canister ? is that the 'charcoal canister' people go on about thats in the engine bay, which is long gone on my car.

[4v8s]

are they defo the same as in 3rd gen versus 2nd gen?

because I thought it may depend on whether the fuel system/tank is pressurised or not depends on whether you have a vented or non vented type filler cap? Perhaps you are supposed to have an unvented cap on your car but you have a vented type? whuch would let some vapours out potentially and also mean you didnt get the hissing. The hissing is because the system with the charcoal cannister etc is pressurised so it makes a vacuum in the fuel tank so the vapours are sucked into the cannister and then used by the engine intake later.

[SUPERCHARGEDGTA]

any car fitted with charcoal/carbon canister has the same cap (lots of euro cars did to, like rovers )

[Newcastle knight]

it doesnt look like a vented cap, theres no vent holes or anything on it, my old one looked pretty much the same too.

I changed the old one as the hiss started disappearing too and i thought it was the cap as when i inspected it the rubber seal had lots of cracks in

[4v8s]

any car fitted with charcoal/carbon canister has the same cap (lots of euro cars did to, like rovers )

haha, well as th owner of two Rovers, i wont take offence at that especially knowing the ZT V8 would run rings around any yank then eat it for breakfast. although it is powered by a Ford Mustang 4.6 lump)

anyway, dont some earlier 2ng gens not have the charcoal system so would be a differnet cap?

also, the non vented type I thought had a sort of pressure releif thingy in them that would vent if the vacuum got too high?

but yes it sounds like you have a leak in your fuel system somewhere - even a tiny hole in the tank etc would potentially cause your issue. I had this on my Rover! (the 18 year old one mind - nothing a bit of POR15 couldnt fix )

[SUPERCHARGEDGTA]

I was thinking more rover 214

[Newcastle knight]

oh great a leak in the fuel system, just what i dont need.

[SUPERCHARGEDGTA]

could be a leak in the breather pipe/hose only (it is metal pipe most of the way) could be rust pin-hole, loose hose clamp or hose split/perferated
if it was fuel you would see it

[Newcastle knight]

well i didnt get a chance to check into it properly today but with the car running, theres a constant hiss coming from the petrol cap area, so i stuck my head up under the rear wheel and you can hear it from up past the endlink on the swaybar, im guessing thats where the fuel pipe is your on about John ?

[SUPERCHARGEDGTA]

yes, the vac. hose is up there

[Newcastle knight]

ok cheers john, looks like that will be tomorrow nights task ! is that the metal pipe with a rubber hose on it, and i think theres some sort of round black thing near it too ? (i think)

[SUPERCHARGEDGTA]

there is 3, one fuel out from pump, 1 return from fuel rail (these come from engine bay together) and one breather

[Newcastle knight]

ah right, well i shall have a poke and a prod, if i do it with the car running and run my hand around the pipe i should be able to feel the vapour escaping and hopefully sort it out with something............like a big bloody hammer ! damn car