Jump to content
SAU Community

Recommended Posts

I hate it when my car makes PSSH noises, but the one I have noticed is not evident, which probably should be, is the fuel cap. No matter how much, or how little, fuel is in the tank it just doesn't go pssh when I open it. All our other cars do. I have been getting a strong smell of fuel in the cabin and someone said it could be the fuel cap. What are the causes to this?

Ive swapped another fuel cap in there from my old skyline which I am 110% certain went pssh when I opened it but haven't driven the car yet to build up pressure in the tank.

Could there be another issue? I'm not having any issues with the car, just this smell on start up and the only noticed this when the dude told me to try it out. Injectors are not/should not be leaking as I am not running rich enough to cause starting or firing issues anymore, and they are using all brand new seals all round.

Its an R33 GTS25T lol. Is it normal for it to go pssh or does it not matter if it does or doesn't.

Link to comment
https://www.sau.com.au/forums/topic/372701-fuel-cap-doesnt-go-pssh/
Share on other sites

pretty sure mine did, but it was so long ago now. my current car doesn't and i've been thinking about getting a new cap to see if it makes it hold pressure a bit more as it may also improve my fuel economy a tiny bit.

in your case it may be the cap that is the issue (or more to the point, the little rubber o-ring on it) or possibly the rubber seal around the top of the fuel tank where the fuel pump is accessed.

It may possibly be the fuel cap insert fitted during compliance. It is fairly common for this to leak.

Its the part that the fuel cap screws into. It needs to be pryed out, cleaned and resealed with gasket goo. Refit and try not to move it for 24hours or so to let the goo set properly

Thats what I would like to know too. Its clearly holding pressure so one would assume it would have an effect on the overall fuel system if there is no pressure in the system. Tomorrow ill be fixing mine by gooing up the hose as JEZ suggested.

I know that when my car is parked, I can see the air hazy around the fuel cap area, when the lid is on. So there is definitely something going on there.

Edited by SargeRX8

only way that a fuel cap can affect fuel pressure is if it is creating a vaccum as the fuel level drops. if this is happening then you would get the "psssht" when you open the cap as it would have to seal tightly. other than that, all fuel pressure is controlled by both the fuel pump and the fuel pressure regulator. if the fuel pump is dying then it won't be able to supply enough fuel and pressure will drop. if the fuel pressure reg is shot then it will simply make the fuel pressure be wrong.

only way that a fuel cap can affect fuel pressure is if it is creating a vaccum as the fuel level drops. if this is happening then you would get the "psssht" when you open the cap as it would have to seal tightly.

In addition to this, if you equalise the pressure in your fuel tank during the warmth of the day, then the air in your tank cools at night you will create a vacuum. In fact I'd say thermal expansion and contraction would play a bigger part in your psssht factor than a dropping fuel gauge.

There's only supposed to be two ends in your fuel system; Out of the filler, and to the motor. So If you haven't got any fuel leaks I think we can rule out the submerged/pressurised side. Leaving the filler. I agree with what has been said about your filler cap seals, or possibly a leak in the tube running to your tank. But again, if it's not leaking when you fill up, it can only leave the seals. Try a friends functioning filler cap.

I am aware that is is the pressure of expansion of the fuel in the tank which causes the psssh but it must be going pssh for a reason and Nissan must have designed it as a sealed system for a reason. I just like it when things operate the way they should. Maybe it won't do shit to the car but I don't know, its just the little voice in my head that somewhat seeks normalisation/perfection. If I hear a single squeak or rattle in the car, I'm under it for days trying to check out the cause. Thats just me lol.

The vapor canister is all hooked up. Its a replaced unit(unsure why it was replaced, possible due to damage when the car was majorly guttered). What should I be looking at? They are cheaper than chips to buy and if this could be causing my lack of psssh ill replace it.

having it fully sealed has 2 benefits. 1 is a side effect of the other. the main reason being that there is no fuel vapours leaking around the car (so if someone walks past with a cigarette in their hand it won't go boom). the side effect of this is that when it is sealed there is a limit to how much fuel can turn from liquid to gas, thus helping with fuel economy.

Today I started the car while the car was facing a southern direction so the sun was behind me. Immediately as soon as the car started I saw the fuel haze coming from the petrol filler cover and the smell hit the cabin straight away. It is definably something going on in there. I doubt it is the cap as I am using two caps, one definitely working from my old car and both rubbers are still fine etc.

I'm gonna try to what jez said, clean the shit out and reseal it. It really did not look safe because if there was any spark or flame in that area the car will go boom.

It was pretty easy. Open the fuel cap and determine if you need to seal it. The metal thing which you put the fuel filler into, and the thing you screw the cap into, comes out. Mine came out WITH EASE. There was literally nothing holding it in place. I pulled it out and cleaned it up with a wire brush and screw driver(when you get it out you will see gunk and shit around the inner lip which holds to the tube you pulled it from). Get some gasket goo stuff which is suitable for use on parts which handle petrol. When you pull the metal thing out of the car and flip it up side down, there is like a U ridge. Fill the U ridge with your gasket goo stuff(I used permatex form a gasket). Apply some to the black tube in the car. Be careful not to drop shit into your fuel tank. Let it set til its tacky then insert it back in, push it down and put your fuel cap back on and let it dry. I drove the car about 1hour later. I didn't want to open the fuel cap to see if it worked so I wanted til the next day and the seal was set. Took the lid off PSSSSSSH.

I'm gonna drop a full tank in there today and see if it has any effect on fuel economy at all. Currently do about 240 - 280 a tank but never let the car fuel gauge drop to the E.

Absolutely no more smell of fuel in the cabin!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Ok i will get those 310mm. I found one but on a different site. This is the description on those...is it ok? Technical parameters: - Axle: front. - Disc type: ventilated. - Number of holes: 5. - Disc diameter: 310mm. - Total height with center: 54mm. - Thickness (new/min.): 30/28mm. - Designed for brake calipers manufacturer: Sumitomo.
    • You Gregged a whole racetrack!?
    • Look for broken wire or bad connector at the motor. Might not be it, but is worth starting there, as it is easy.
    • Hi everyone, I’m having an issue with my R32 GT-R. Sometimes, when the car goes over a bump or experiences some vibration, the 4WD warning light comes on the dashboard. When I check the code from the control unit in the trunk, it shows Code 19 – ETS Motor. However, everything seems to be working fine — if I turn off the engine and restart the car, the light goes away and everything functions normally. Has anyone experienced this before? Where should I start troubleshooting this issue? Thanks in advance!
    • I'm back from the dyno - again! I went looking for someone who knew LS's and had a roller dyno, to see how it shaped up compared to everything else and confirm the powerband really is peaking where Mr Mamo says it should. TLDR: The dyno result I got this time definitely had the shape of how it feels on the road and finally 'makes sense'. Also we had a bit more time to play with timing on the dyno, it turns out the common practice in LS is to lower the timing around peak torque and restore it to max after. So given a car was on the dyno and mostly dialled in already, it was time for tweaking. Luis at APS is definitely knowledgable when it came to this and had overlays ready to go and was happy to share. If you map out your cylinder airmass you start seeing graphs that look a LOT like the engine's torque curve. The good thing also is if you map out your timing curve when you're avoiding knock... this curve very much looks like the inverse of the airmass curve. The result? Well it's another 10.7kw/14hp kw from where I drove it in at. Pretty much everywhere, too. As to how much this car actually makes in Hub Dyno numbers, American Dyno numbers, or Mainline dyno numbers, I say I don't know and it's gone up ~25kw since I started tinkering lol. It IS interesting how the shorter ratio gears I have aren't scaled right on this dyno - 6840RPM is 199KMH, not 175KMH. I have also seen other printouts here with cars with less mods at much higher "kmh" for their RPM due Commodores having 3.45's or longer (!) rear diff ratios maxing out 4th gear which is the 1:1 gear on the T56. Does this matter? No, not really. The real answer is go to the strip and see what it traps, but: I guess I should have gone last Sunday...
×
×
  • Create New...