C2 gas fumes

[Randy S.]

I recently arranged to store my 66 327/300 at a neighbor's house as we downsized to a 2 car garage when we moved to Oregon. She has been complaining of the gas fumes.

I guess I just learned to live with it when it was garaged in our 3 car garage in Georgia.


A search of the archives revealed it is the nature of the beast made worse by today's E10 fuels. But I have a few questions that I could not find in the archives.

1 It appears to me the vented fuel cap releases fumes thru the tank overflow tube. Couldn't this be plugged while in storage to minimize the smell? I noticed the rubber gasket on the cap is pretty hard but since the cap vents the fumes anyway I would think a better seal at the tank neck isn't going to help minimize fumes.

2 Is there any absorbant material than will minimize the odors like cat litter, baking soda, etc?

FYI I have the stock 3367 Holly carb which I understand is vented.

Randy

[Paul Y.]

Re: C2 gas fumes

I don't believe gas fumes that you can smell are normal. I think that gas is leaking somewhere and that when you find it and repair it the fumes will stop. The carburator is probably the least suspect while it is being stored as the fuel evaporates and does not continue to overflow from a float that is not properly adjusted. I suspect the fuel sender o ring or the two rubber hoses (one by the tank and one by the fuel pump), or the tank itself could be the culprit with just a pinhole in it. If you remove your spare tire carrier you will be able to examine it at the bottom easily. Like others have mentioned, you can do an easy examination from the top with a flash light. The gasket between the cap filler and the tank could be the culprit. Does the car require a lot of pumping and cranking to start after storage? The fuel pump check valve may be defective and the fuel drains back to the lowest area in the line. I would examine the fuel pump closely also for signs of leaking. Are all the steel fuel lines tight? It doesn't take much for fumes to smell but I believe more than the factory vent systems for sustained odors.

[Daniel N.]

Re: C2 gas fumes

She has been complaining of the gas fumes.

Are you absolutely certain that the gas cap is properly seated? I had this "problem" until someone pointed out that the cap wasn't threaded correctly. It's hard to spot by eye.

[Stuart F.]

Re: C2 gas fumes

Your 66 should have the two way vented cap, i.e. a pressure relief valve and a vacuum valve. A 63, like mine, just had a simple vent hole in the cap and I changed mine to the later cap like yours should be and it helped some (not a cure).

Believe the advice to check for small leak should be followed. The usual problem we all have due to the fuel occurs just after shut down when both the tank and the carb vent. After that, any smells should be checked for further, i.e. days later, etc.

Stu Fox

[Harry S.]

Re: C2 gas fumes

Also take a look at the fuel pump.

[Rich G.]

Re: C2 gas fumes

My 66 327/350 is in the attached garage 3 feet away from where we sit and watch TV with just a door between. It does not smell of gas. It DID once and it was a fuel sender leak, not enough to see, but enough to smell. Fixed that and a while later, smelled again and it was the fuel pump weeping.

So, as stated above, check those spots.

Rich

[Gary J.]

Re: C2 gas fumes

All good advice, defintely drop the spare tire tub and examine the entire gas tank, I found that someone had repaired my tank with fiberglass and body filler and the repair was hidden directly above the frame cross brace. Of course, fiberglass mat and filler are NOT gasoline resistant and it was just a matter of time. "Bubba meet gas tank repair." Replaced tank and sendng unit, gained peace of mind. Happy Holidays.
Gary

[Randy S.]

Re: C2 gas fumes

I don't believe gas fumes that you can smell are normal. I think that gas is leaking somewhere and that when you find it and repair it the fumes will stop. The carburator is probably the least suspect while it is being stored as the fuel evaporates and does not continue to overflow from a float that is not properly adjusted. I suspect the fuel sender o ring or the two rubber hoses (one by the tank and one by the fuel pump), or the tank itself could be the culprit with just a pinhole in it. If you remove your spare tire carrier you will be able to examine it at the bottom easily. Like others have mentioned, you can do an easy examination from the top with a flash light. The gasket between the cap filler and the tank could be the culprit. Does the car require a lot of pumping and cranking to start after storage? The fuel pump check valve may be defective and the fuel drains back to the lowest area in the line. I would examine the fuel pump closely also for signs of leaking. Are all the steel fuel lines tight? It doesn't take much for fumes to smell but I believe more than the factory vent systems for sustained odors.

Paul and others,

Thanks for the tips.
Maybe I don't understand the operation of the gas cap. Does it ALWAYS vent fumes to atmosphere or only when there is significant pressure to overcome the valve in the cap? I was assuming always but maybe this pressure exists only after running or in higher temperatures. Someone enlighten me.

I checked the seal at the sender and that looks dry as does both the rubber fuel lines to the fuel pump.
I am thinking a replacement fuel cap may be a good investment.

Do I have it right that some venting is normal after the car is first shut down but that later there isn't sufficient pressures to vent the tank or the carb and the odor should dissapate?

Randy

[Jack H.]

Re: C2 gas fumes

Once the car has cooled down after being run and temperature in the tank is normalized to ambient, there should be little/no discharge of gas vapor from the tank through the cap.

The lion's share of fuel out-gassing should arise from the vent stacks on your carb(s) fuel bowl(s). That's just the nature of the beastie...

Many a-wife simply doesn't understand the difference between a classic car with carbs and their modern daily driver which has FI and a TOTALLY sealed fuel system. Most attempts at explanation are simply an exercise in futility.

Carbs don't work unless the fuel pressure is normalized to ambient before it's jetted to effect the air/fuel mixture ratio. Hence the fuel bowls HAVE to be vented and they WILL out-gas what fuel is stored via evaporation during storage intervals...

Now, if you have other problems, you need to address those. Here, are some of the more common issues:

(1) Carb(s) leaking with raw gas dripping into or onto the intake.
(2) Integrity issues with the tank and/or fuel lines.
(3) Owner 'training' -- insists on 'topping off' the gas tank before vehicle storage which overfills the tank to reduce/elminate vapor expansion space.