Air trapped in petrol tank

Forum for Engine, Exhaust, Drivetrain, ECU
Post Reply
jrob24
Posts: 3
Joined: Fri May 11, 2018 6:37 am
Qashqai Model: Mk.2 Qashqai - J11 (2013–2017)

Post by jrob24 »

Hi folks
I have a 1.2 64 plate Qashqai. When i remove the petrol cap there is an unusually long escape of air. I've had cars in the past that have a small blast of air when you do this but my Qashqai can sometimes have up to 3-4 seconds of escaping air. Any ideas?

User avatar
MikeGC
Posts: 1852
Joined: Tue Feb 07, 2017 11:50 am
Location: Stockport
Qashqai Model: Mk.3 Qashqai - J12 (2021+) New Model

Post by MikeGC »

In my humble opinion this is air rushing into the tank.
Assuming you fill the tank completely and screw the cap on tight, you might find no air can gradually "leak" into the tank.
March '22 - J12 1.3DIG-T 160 CVT Tekna+ with all wheel drive - Pearl Black
July '19 - J11B 1.3DIG-T 160 DCT Tekna - Vivid Blue
March '17 - Qashqai J11A 1.5dci n-connecta - gunmetal
September '14 - Juke 1.5dci gunmetal ascenta premium (red accent packs)
tophat57
Posts: 78
Joined: Sat Dec 30, 2017 10:42 pm
Qashqai Model: Mk.2 Qashqai Facelift - J11b (2017–2021)

Post by tophat57 »

Blocked fuel system somewhere. There must be a return pipe (or vent tube somewhere) to allow air into the tank to replace the fuel that has been used. Otherwise the fuel tank would be under an increasing vacuum as the pump draws more and more fuel from it. Eventually the pump would likely stop, as it wouldn't be ble to overcome the negative preasure of the tank. And you probably wouldn't be able to remove the filler cap. So probably not a total blockage, but would be my guess.
Facelift J11b N-connecta 1.6 x-tonic in vivid blue. And a dual accelerator for my dodgy foot..........
DaveBerlin
Posts: 8623
Joined: Wed Mar 19, 2014 12:39 pm
Location: Berlin, Germany
Qashqai Model: Mk.2 Qashqai Facelift - J11b (2017–2021)

Post by DaveBerlin »

We have had this “ Problem” since new 2014 and never really questioned this. I normally “Fill Up” before the Warning comes and yes when I open the tank there is a Rushing of Air, just checked our QQ 3/4 Full now - no noise ! - Dave :D
11.19/1.3L/160PS/Tekna+/DCT/PrOPILOT/KAD Gun Metallic/Trunk Lower Finisher/Rear Glass Finisher/Ambient Lighting-LED’s Innen/Entry Guards Illuminated/Sport Pedals/Front Styling Plate/LED No.Plate/Chrome Door Handles/Rear Valance/Giacuzzo Alloys + Falken
jrob24
Posts: 3
Joined: Fri May 11, 2018 6:37 am
Qashqai Model: Mk.2 Qashqai - J11 (2013–2017)

Post by jrob24 »

If there was a major fault somewhere, is it not likely that I would start to notice a drop in engine performance in some way.

I should have said that if the car has been going and then I stop to open the cap, you get the air escaping. Once the car has been sitting for a few hours, when you open the cap there is no air. Would i be right in saying then that air is not being completely trapped.

When you look at the fuel filler cap, just underneath it there is a tiny hole. This hole is covered by some kind of membrane. You can poke something small through it but then the membrane just closes over again. Does this have anything to do with the flow of air?
Deleted User 3871

Post by Deleted User 3871 »

The fuel tank probably has an anti syphon system that may be restricting the air flow. For some cars there is a one way flap inside the fuel pipe just incase the owner forgets to put the fuel cap back on, this stops fuel loss going around corners.

I'm guessing it may be one of these.
jrob24
Posts: 3
Joined: Fri May 11, 2018 6:37 am
Qashqai Model: Mk.2 Qashqai - J11 (2013–2017)

Post by jrob24 »

thanks.....
do you know if there is a way i could check this myself or will it be a garage job?
Deleted User 3871

Post by Deleted User 3871 »

I guess you could by one of those endoscopes from Amazon for £20 - £30 , but to be honest a good garage should be able to tell you. Good luck finding a good Nissan garage though, lots of people complain about them.
jrob24 wrote: Fri May 11, 2018 11:43 am thanks.....
do you know if there is a way i could check this myself or will it be a garage job?
dani87
Posts: 60
Joined: Fri Aug 22, 2014 11:05 pm

Post by dani87 »

This is normal. If car has been running for a while and you remove cap you do get the rush of air. It happenes to every petrol car i pdi at work.
Post Reply