No whooosh at the gas cap...

[e21pilot]

Today I took my 1980 for a fill up and noticed that there was not whooshing sound when I removed the gas cap.

Does this mean I have a vacuum leak somewhere? Idle quality still seems to be fine. Is this something I can ignore or at least deal with in my spare time?

 

[want2wheel]

I would say "no" in short. This depends on the type of tank, home much fuel you used, and what the ambient temp was.

 

[shawnfj40]

It could mean all kinds of things. Most of which you need a smoke machine to find.

 

[Landpimp]

No whoosh is good, unless it's fuel injected.

A big whoosh is bad...

 

[77mustard40]

No whoosh is good, unless it's fuel injected.

A big whoosh is bad...

Not to high jack, but why is that bad? What's the cause and what are the solutions?

 

[ginmtb]

My tank was pressurizing so much so that I could hear the metal tank "popping" from the expansion. My check valve to the charcoal canister went bad. I removed it and no longer have the pressurization issue and didn't notice any performance drop from not having the check valve. I have read about tanks blowing apart at the seams. Not good!

 

[FJ40Jim]

It means there is a leak somewhere in the fuel tank or vapor system. If it's just a bad check valve in the canister then it's nothing to worry about. If it a leak in the tank or a hose, that could be a concern.

 

[77mustard40]

So Jim, I converted several years ago back to a stock carb and still have my canister on my 77. When I'm low on fuel and/or if its warm out and I've been driving , I will get us buzzing hum from the area of the fuel separator. If I open the cap, there will be a release of pressure. Do I need to go through my separator?

 

[FJ40Jim]

The system is supposed to hold some pressure in the tank, to help keep gas from boiling. If the cap shoots across the garage when removed, there is too much pressure. If it just releases 15gals. of slightly pressurized gas vapor, then it's OK.

 

[77mustard40]

Thanks, there is a pressure release but nobody is getting hurt when you open the cap

 

[sadam_husain]

No whoosh is good, unless it's fuel injected.

A big whoosh is bad...

both my fuel injected cruisers stop going if there is too much whoosh in the tank (vacuum) the external pump starts to cavitate and I lose fuel pressure on the fuel rail, it used to happen all the time on longer trips, I had to drill 1.5mm holes in the fuel caps to let the pressure equalise and never had a problem since

 

[e21pilot]

Lots of posts here...just so I understand, if everything were working normally for my 1980 2F (which still has to pass the CA smog test), After driving a long way and consuming most of the gas in the tank and then shutting off the engine, should there be a vacuum in the tank or a positive pressure? If I no longer hear a whooshing sound, than I have a leak somewhere and most likely will fail the smog test, probably the evap portion of it. Also, where is that check valve for the evap located?

 

[shawnfj40]

You should look really close at the fuel/vapor separator on the pass side b-pillar. The little plastic nipples on it are prone to snapping off.

 

[N919HJ]

This is my whoosh. It has been sitting since Sunday. The tank is about half full. It is currently 23 degrees out. I don't know if it is bad or good. Thoughts?

 

[e21pilot]

Thanks for the whoosh video. I think when I had whoosh, I had even more whoosh than that on my 1980.

 

[ginmtb]

Mine didn't sound that loud but when you hear the buckling of metal (the tank) you know that can't be good. This was while it was sitting there in a nice cool garage.

I have no woosh now - @FJ40Jim you mentioned boiling gas. I'm wondering if I should add a replacement check valve to the system.

 

[N919HJ]

Mine feels more like a vacuum is being created. I'm going to check it again after the next time I drive it. It has been a while since it has been warm here. But I feel like when it is cold it creates a vacuum and in the summer it becomes pressurized. I'll report back.

 

[e21pilot]

When I had whoosh, it seems to me it was always vacuum in the tank. I remember it being louder, longer when I ran the tank nearly empty like on a long road trip -- just my $.02 however, I don't have any empirical measurement to back this up.

 

[todt]

My 82 sounds pretty close to that video and always has. Sometimes longer. I'm dealing with fuel delivery issues at the moment so been knee deep in trying to understand WTF. Checking fuel vapor separator is next for me.