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fuel tank

E

E M Wynne

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Location
Netherlands
Car
2001accord 1.8is
Guys, My fuel tank has started to pull a vaccum when the engine is running & releases on opening the fuel cap...I,ve tried cleaning the cap & what looks like a 1 way valve on the top off the cap...appart from running with the cap loose I can,t find the problem...anyone had this before.
Cheers Eddie.
 
I can hear a rush of air when i open my filler cap but after reading the owners manual this appears to be normal, not sure if thats what you mean?
 
I also ear that in mine, guess its normal. I think it's the petrol gases that form inside the tank.
 
Yep I get this as well and it's normal when filling the car up.
As said its probably just air or the gases escaping
 
Guys, I did not get this effect before, & I,ve had the car a year now...it is definately air rushing IN & not fuel vapour or air coming out...the pump is suppling fuel to the engine but in doing so is causing a vaccum in the tank...there should ALWAYS be a vent in the tank & fill system...if you look closely at the fuel cap there seems to be a 1 way valve...normally a ball & spring but I can,t seem to move or be able to clean it...maybe just buy a new cap.
Cheers Eddie.
 
All 4 of my cars, including my 6th Gen Accord, do this if I run them from a full tank to empty. As far as I know it's normal - I understand the vent in the tank & fill system is to release pressure from inside the tank on hot days or when there is a lot of vapour in the tank, it's not for sucking in air.
 
The vent is there so there is atmospheric pressure on top off the fuel IN the tank at all times.
Eddie.
 
I think every car I've ever owned has done this. It doesn't do it all the time though mostly when doing a long run and having a near empty tank. IIRC my Supra and MG did it more than any other, massive HISSSS when you open the cap.
 
Definitely normal to have a slight vacuum form above the fuel contents - keeps the fumes from escaping. Usually there's a control valve inside the cap making sure this vacuum doesn't become excessive as the tank empties. Wifey's MR2 roadster has a very complex breather arrangement connecting the fuel tank space to the inlet manifold, under the control of the ECU.

But it is odd that the OP hasn't noticed this before - maybe there was a problem with the cap previously not letting the vacuum form. Just a thought...
 
Every one of my car has done this. It's more prominent the emptier the tank gets. You're worrying over nothing!! The fuel tank pulls a vacuum due to the suction of the fuel pump. The air pressure difference between the inside and outside of the tank is incredibly small, but due to the size of the tank causes what seems like a rush of air when you release the cap. hence why this effect is more noticeable on a empty tank.

As part of the MOT your fuel cap has to be air tight. This is in case your car rolls during an accident to eliminate fuel spillage. Modifying the cap or running with it loose is dangerous and makes your car unroadworthy.
 
It's not an issue at all. Both my cars do this. To be honest i think you're worrying over nothing mate.
 
If you look on the Lings microfich there is a vent pipe, part 17 on the drivers side of the tank...I,ll have to get the wheel off & have a look.
Eddie.
 
The vent pipe is not going to be open ended. It's likely it will have a pressure release vale on it.

But as said you're worrying over nothing, it's completely normal.
 
Does it on every car I have owned, very normal, if anything, I am glad to hear it, makes me realise I was running low lol :lol:
 
On another note...does anyone in the UK. supply an aluminium radiator, for engine only...I,m changing to a manual gearbox & doing away with AC.
Cheers Eddie.
 
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