gas tank question

[a2012fatboy]

hi everyone love this site been helpful so far so my question is do i need to have an air vent on my 3 gallon gas tank? it's a portable red gas tank but i've seen no air vent on it what so ever i was just wondering if that would affect the performance on my 40 hp evinrude thanks for any advice

 

[metriccrescentwrench]

The portable tanks I've seen have vents built into the fuel cap. Some are always open and some are such that you have to unscrew the vent to open it (if you forget to do so the engine will run perfectly fine for a while and then slowly quit as the fuel pump can no longer pull fuel from the tank - guess how I know !!! ).

 

[MH Hawker]

Its in the cap, but depending on the age of the tank it may need to be opened manually or if its a new CRAP tank its self venting.

 

[a2012fatboy]

ok thanks not really sure which one i have but my motor hasnt died on me would it hurt it if i put one myself?

 

[airshot]

If your motor has not died then it is already there, why add another?

 

[a2012fatboy]

ok thanks for all the help

 

[Silvertip]

The answer to your real question is "yes -- any fuel tank needs a vent to let air in to replace the fuel that has been sucked out." The example of what happens when there is no vent is to suck real hard on an empty plastic soda bottle. The sides cave in do they not? While your tank may not collapse without a vent, the primer bulb would go flat and the engine would stall. That's the physics lesson for today. But as was pointed out, if your engine is running fine there is no need to add one. No portable tank manufacturer in their right mind would design a tank that is not vented. There were some old two line OMC tanks that had no vent but that was a very different fuel delivery system.

 

[a2012fatboy]

awesome thanks everyone for the help