Moeller 12 gallon fuel tank - venting?

[KC8QVO]

I am not sure if I am posting this in the right forum, but I didn't think it went under the Engine category or Building... I got one of these tanks to run this season and am noticing a bit of a problem - I think. When running the tank collapses and at some point the motor starts cutting out (1993 Johnson 25hp). When I open the cap the tank fills back in a bit and the motor runs without an issue for a while. Is this something that just happens to be a part of my set up? Any ideas?

 

[jbcurt00]

That motor NEEDS a vent open on the tank while running, not closed. Thats why tank collapses when its run w the vent closed, vacuum created by pulling fuel out of a sealed container. Then the tank regains its shape when you open the vent, allows air in, eliminating the vacuum.

Perhaps you've got the wrong cap on the tank, if theres no vent elsewhere on the tank, in the top of the cap, or the wrong tank for your motor.

Did you buy the tank new?

Is there a small knurled knob looking vent cap that can be opened on the top of the tank's cap?

 

[gm280]

KC8QVO, not sure the exact type fuel tank you have, but I have their 6 gallon version and the gas cap itself has a little knob like top section that you have to open when using it so air can fill in when the fuel is being sucked out. If you didn't open that, the tank will collapse until the engine stops. So check your cap and/or post a picture for us to see. I believe you can open the vent on the gas cap and solve your problems... JMHO!

 

[82rude]

I have the same tank or at least the same brand and gallons and you need to pop open the vent when running your motor.My vent is right on the cap and on the one occasion I forgot to vent my etec collapsed the tank in 1/2 .You have to leave the vent open when running.

 

[KC8QVO]

No Title

12 gallon topside, regular profile. It is the one on the bottom.

 

[Silvertip]

How a tank vent works is as simple as sucking real hard on an empty soda bottle. Unless it is vented, it collapses. Your tank must be vented when running for the same reason..

 

[TruckDrivingFool]

That is a different style of cap than they show on the Moeller tanks. Though they look to be in the same family I did find some pics of Scepter tanks that had the same cap (the Scepter site even shows the same cap as Moeller now)

Perhaps there was a design flaw in a self venting cap and thats why the caps in pics for new tanks are different. If the center nub on the fill cap that the keeper strap attaches to doesn't twist open for a vent I'd contact Moeller/Scepter and ask them how that style of cap is suppose to vent.

How to fill and store your Moeller/Scepter tank About 3/4 the way through they show the other cap style and the vent and that's why I mention the tab in the center of that style cap.