Need an air vent???

[iggyw1]

I need this answered. I have an older (1982) 70 H.P. 2 cycle Johnson motor. Runs great! Here is my question. There seems to be no air vent on my 6 gallon gas tank for this motor. Is it suppose to have an air vent that is suppose to be open when the motor is running? I keep the fill cap closed 100% when running. The gas tank actually builds up a pressure when the sun is shining and its hot outside. There is only one (single) gas hose from the tank to the motor and no air vent, and the motor runs excellent whether the gas filler cap is tight or loosened a little bit. Is that cap suppose to be loose?? Thanks!

 

[Bosunsmate]

Depends:laugh:
Some newer tanks have self vents built into them. Look for some little holes around the outlet connection on the tank

 

[Bosunsmate]

Mine has a self vent, it builds up a little pressure in the sun and doesnt get sucked flat during use

 

[Joe Reeves]

Many of the factory 6 gallon fuel tanks have two small pins protruding from the fuel connector fitting on the tank itself. When you plug in the fuel ling connector, that causes those two pins to be pushed in slightly. The "pins" are actually valves.... one being to open the fuel flow, the other to open the air vent.

 

[GA_Boater]

Do you have one of the newer "EPA" plastic tanks? They are self-venting and no need to loosen the cap. I find that all plastic tanks, even the plastic gas cans expand in the heat, no matter if they have a separate vent or not.

 

[F_R]

Environmental laws say they cannot emit fuel vapors into the atmosphere. Therefor, any tank vent must be one-way, letting air into the tank, but not letting any out. That is why it builds up pressure in the sun.

 

[iggyw1]

Many of the factory 6 gallon fuel tanks have two small pins protruding from the fuel connector fitting on the tank itself. When you plug in the fuel ling connector, that causes those two pins to be pushed in slightly. The "pins" are actually valves.... one being to open the fuel flow, the other to open the air vent.

This is the type that I have, so it is in fact being vented as long as the hose is connected and pushes those pins in. Thanks!

 

[iggyw1]

Environmental laws say they cannot emit fuel vapors into the atmosphere. Therefor, any tank vent must be one-way, letting air into the tank, but not letting any out. That is why it builds up pressure in the sun.

So even the tanks with the little valve in the center of the filler cap that you unscrew to open only lets air in and not out??

 

[F_R]

So even the tanks with the little valve in the center of the filler cap that you unscrew to open only lets air in and not out??

No, I'm not saying that. Those types probably are in non-compliance with current laws. I suppose grandfathered in so you can use them though. Some states are more picky than others (California, for instance). Speaking of emissions though, even the hose must not let any seepage or vapors through their sidewall now. That's why they are so expensive.

 

[iggyw1]

No, I'm not saying that. Those types probably are in non-compliance with current laws. I suppose grandfathered in so you can use them though. Some states are more picky than others (California, for instance). Speaking of emissions though, even the hose must not let any seepage or vapors through their sidewall now. That's why they are so expensive.

They are probably more expensive too because they are made of a material that will withstand the damages caused by fuel with ethanol in it. The older hoses and fuel lines get eaten up by the ethanol!

Also, I just purchased a 5 gallon plastic gas can (not a tank , but a gas can) for carrying gas in to put into my lawnmower. It has no air vent on it like the older gas cans have (probably due to the emissions laws) and it is a real SOB to get the gas to come out of this gas can and into the lawn mower's gas tank!!!!