Fuel Fill / Vent Cap

[wacres98]

Hi. I have a below deck fuel tank on my 22" center console. The fuel fill and vent hoses go up to a combo fuel fill / vent with a cap at the transom. When the cap is screwed on it forms a water tight seal. So how does the fuel tank vent when the cap is on because it provides a tight seal? Thanks.

 

[robert graham]

Re: Fuel Fill / Vent Cap

Upon close inspection the cap may have a vent built into it that allows air but not water to enter the tank. Otherwise there may be another vent line somewhere not visible. But rest assured, your tank is vented or the motor wouldn't continue to run.

 

[Fireman431]

Re: Fuel Fill / Vent Cap

You didn't list what engine you have and whether or not it's fuel injected.

The vent under the cap may be just for fueling up and if you're engines fuel system has a return line, that would allow the tank to breathe during operation.

 

[dockwrecker]

Re: Fuel Fill / Vent Cap

Nope, the vent is below the cap, not in the cap. The cap is supposed to be watertight. The vent at your thru hull should have a flapper in it of some sort. Your vent connets below the fill point, usually just below the filler cap. The vent doesn't seal for vapor, but will close somewhat under water pressure. Some vents don't use a flapper at all, but are located high enough to prevent getting wet while running. Be careful while washing not to direct a full spray at the vent.

 

[oldfordcrap]

Re: Fuel Fill / Vent Cap

on my boat the overflow serves as the vent it has a small through hull stainless fitting wth a screen to prevent clogging bugs,ect

 

[dingbat]

Re: Fuel Fill / Vent Cap

I have the same "vented" cap on both my tanks.

If you look very closely at the bottom of your cap you'll see a little vent plunger hanging from a hole. The hole is your vent and the plunger is your surge valve.

The cap is actually two pieces. A "lower" cap that seals the fill hole with an o-ring and a ?top hat? which covers the entire assembly. The vent is between the lower fill cap and the ?top? hat section and uses gravity to keep the water out of the fill vent.

They work very well unless you install the fill in a well where the water can puddle higher that the cap. Then all bets are off. I learned that one the hard way.

http://www.iboats.com/Perko-Combination-Gas-Fill-Tank-Vent/dm/view_id.237346

 

[I Fish]

Re: Fuel Fill / Vent Cap

Not trying to hyjack here, but I just bought the same fuel fill. Before installation, I wondered the same thing. I blew through the vent pipe, and it allowed me to blow and suck. It's not like an open pipe, but it did allow air flow in both directions. As far as I can tell, it needs to be mounted like dingbat suggested. Mine didn't have any instructions, so I was wondering if your fills are grounded?