Gas tank pressure?

[nienberg.11]

Mine's not that severe, but it hasn't been so easy to deal with since the stock vent line is open to the atmosphere and pressure is still building in the tank. I tried to clear the line by unscrewing the gas cap and blowing compressed air into it, but that didn't work.

[Tony D]

That should have read "there is a manometer reading that must be reached before the carbon cannister admits fuel VAPOR"

 

Point being that there ARE acceptable amounts of pressure and vacuum that will be present in the gas tank.

 

In the EARLY cars, the crankcase was the storage for evaporative emissions, and if you have high pressure in the crankcase, it pressurises the tank---especially if the shuttle valve on the left fender well goes south...nothing like acidic crankcase vapors being pumped into the tank....

 

And the point behind saying that is that EVERYONE in this post has given subjective opinions on what pressure is in there.

 

Without actually measuring it, and quantifying it, those kind of measurements are useless!

 

You are taking the right step: MEASURE the pressure buildup, and compare it to what is considered normal.

 

if you have removed the charcoal cannister, you are going to have to vent it, causing massive HC pollution.

 

Emissions are not all out the tailpipe, and as a matter of fact tailpipe emissions are not really a factor in HC vehicular emissions any longer thanks to catalyzation. Now evaporative emissions the what they are going after---and it's precisely what you are discussiing bypassing by adding a checkvavle, or open atmospheric vent to the tank!

 

The charcoal cannister, while being 30 years old, is not a consumable part---it works, and is still in cars today! It does not affect engine performance, but GREATLY decreases emissions from the veihcles when fuel system integrity is maintained properly---there is not any real good reason to remove it.

 

It is easily relocated to the wheel well if you want to clean up the engine bay.

 

Having it there is good for us all. The days of short-sighted emissions hacking should have long been done away with. Legislators watch what people do with their cars, and legislate accordingly. All they need is some media type hyping modifications, and here comes legislation. Clean, Mean, and Green is the hotrodders credo today. Responsible ones, anyway.

 

If we don't police ourselves, trust me, the alternative is someone else like a dimwitted bureaucratic oversight committee legislating draconian measures and killing our hobby...

[kcelectronics]

Well said Tony_D!

[nienberg.11]

Tony, I'm in total agreement with you on the need to keep emissions down. Do you happen to know if it would work to run the vent line straight to the manifold with a check valve in that, or is the charcoal a necessary ingredient?

[cygnusx1]

I wonder if modern day carbon canisters are smaller than a coffee can? If I had room, I'd add one. Many people here, including myself, have removed the carbon canister to make room in the bay for something else. My car is driven so infrequently that it is not a huge pollution contributor especially given the fact that the original post, my post, was about the LACK of venting from the fuel tank.

 

Want to keep emissions down? Let's get America to sacrifice some of it's excessively wasteful lifestyle. Employ the US's environment-saving technologies in other polluting countries. That's the REAL way to deal with environment killing. Stop going after the wounded targets and get the REAL stuff.

[nienberg.11]

A smaller carbon canister is a good idea. I may have to look for one on my next trip to the jy.

[cygnusx1]

And the point behind saying that is that EVERYONE in this post has given subjective opinions on what pressure is in there.

 

Without actually measuring it' date=' and quantifying it, those kind of measurements are [i']useless[/i]!

 

Rough generalization Tony D.

 

The first step in diagnosing would be to identify a symptom and find a relation. Un-quantified "pressure in the tank" is enough information for someone knowledgable in the fuel system in question to diagnose whether or not a normal or abnormal condition exists. It's a simple question. A customer asks: "Is it normal to have pressure in the tank when opening the cap?" It's either "yes" or "no". There is no need to quantify the pressure at this point. If the answer was "no", we test, find, and treat the condition. If the answer was "yes" we go another route and if necessary, we then measure the pressure against a spec.