Technical fuel problem

[georged30]

When i open the fuel filler cup hi presure is released from my fuel tank i think that my fuel tank multifunction valve is stuck. I had a look at haynes manual but i cant find where exactly is the valve located . So i have two questions. Do i have to remove the fuel tank in order to find the valve? I there something else which can cause this kind of problem? My car is a cinq 899.

 

[levemircento]

my sporting does this, its like a vacuum. Does it mainly when tank is getting down past 1/4 way when the cap is opened

not experienced any running problems with it though

I suppose if the tank had a very slight leak, this would not happen as it would draw the air in via the leak [??, maybe??]. I hope I havent just jinxed myself now and am going to get a leaky tank!!

edit: oops sorry, dunno where it is!!

 

[GoBe]

:yeahthat:
This is a fairly common thing, as the tank empties low-pressure is created in the tank and when you break the seal by opening the fuel filler cap air rushes in to equalise tank and atmospheric pressure. It's actually a sign of a healthy fuel system & tank not a bad one. Different car but I'm sure the Punto owners manual actually tells you that you might hear a hiss as you open the fuel cap.

 

[giorgis]

On the fuel tank you get either positive or negative pressure, negative (vacuum) is not possible since one way valve exist to add air in tank, the gas fumes produced in the tank create positive pressure and there is a system with valve opening at 3500 rpm and relieve pressure through charcoal filter and the air intake system.

So if you didn’t run engine up to 3500rpm for a while is normal to have pressure in the tank..

 

[GoBe]

I've just tested my Sei, 1/3 of a tank left, and there was an inrush of air into the tank.

 

[Liam]

The valve is in the top of the tank and the tank needs dropped to access it.

Liam

 

[georged30]

Thanks for the replies you were very helpful

 

[Brooky]

On the fuel tank you get either positive or negative pressure, negative (vacuum) is not possible since one way valve exist to add air in tank, the gas fumes produced in the tank create positive pressure and there is a system with valve opening at 3500 rpm and relieve pressure through charcoal filter and the air intake system.

So if you didn’t run engine up to 3500rpm for a while is normal to have pressure in the tank..

im nearly always running my cinq above 3500rpm except in town,athough the is the slight blip

Excuse the expression but:
I always get a good suck or blow (dont know which) when i open the tank.

 

[K4RL]

Excuse the expression but:
I always get a good suck or blow (dont know which) when i open the tank.

agreed!