A stupid question.

[davegriggs]

I've seen the term 'unvented fuel tank' being used an number of times in posts in relation to problems with badly running outboards. (Which I have). What is an 'unvented fuel tank' and I do I know if I am suffering from this problem.<br /><br />Stupid question Im sure. But I'm quite new to this so your patience is appreciated.<br /><br />Regards<br />DG

 

[Lugnut36]

Re: A stupid question.

Think about it like this most of those plastic fuel cans you can buy nowadays they always have that little yellow tab that you pull off to open a small vent hole, you ever try to fill up your car with one of these cans and the vent is closed? it just gurgles and gas comes out slow but yet if you open that little vent hole the gas flows smoothly. In your outboards tank the fuel delivery opening and hose will not allow air to gurgle back in to fill the "empty" space so you eventually would end up with negative pressure or a vaccuum inside the tank which then begins to pull against the fuel pump. So a seperate air "vent" helps remedy this problem. To test for venting problems just run with the gas cap loose.

 

[steelespike]

Re: A stupid question.

Depending on the type of tank.There is a little thumb screw in the cap that needs to be opened to vent tank.Usually if vent is plugged or not open the primer bulb will collapse as the gas is drawn out of the tank.<br />Let us know the model, horsepower and year of your motor And the details of your problem.<br /> We can be more help.