OMC remote gas can cap question

[johnny-infl]

A fellow member on the Tin Boats site wants to know
how the vent on the cap works – he has an issue of the
tank building up pressure when he stops and squirts gas
out of the gage gasket – he is replacing the gaskets but
wants to address the pressure build up issue.
I have 3 or 4 of these tanks myself and never really paid
attention to the presssure being an issue.

[chinewalker]

Fact is, there is NO vent in the cap. The vent is in the fuel fitting on top of the tank. You’ll see two pins sticking out of the fitting. One is a fuel valve, allowing fuel to exit the tank into your fuel hose. Other is an air vent that allows air into the tank as fuel leaves. There’s a check valve that prevents air from escaping the tank. It is normal for them to pressurize a bit in the sun, warm day, etc. If all your hoses, fittings and carb bits are in good shape, it isn’t an issue. If you’re worried about pressure forcing fuel through the carb or whatnot, unplug the tank when not in use.
I prefer these tanks as they tend to allow less moisture into them, resulting in fewer water in the fuel problems. It is fairly easy and inexpensive to rebuild the fitting if needed.
– Scott

[lotec]

On a related note, on my website is a Tech Tip on replacing the o-rings for the fuel and vent pins on the OMC suction tanks. These often wear or are turned to goo by the ethanol in modern fuels and cause leakage.

Here’s the link: http://www.oddjobmotors.com/tt4_singlelinetanks.htm

[jmar]

Hello all! The question about the tank was mine and the pics. I noticed on the site about the pins being the same length sticking out and realized mine are not equal. The outside pin sticks out about 2mm longer than the one for the fuel. Is that a tell tale problem for the inner workings of the valve? Thanks to Johnny for leading me to this site and helping me on Tinboats. Probably would have gotten my 1979 Evinrude 9.9 up and running quicker if I would have found this. When I get this leak fixed, will I still have to open the cap on the tank each time I stop to fish before making a run to another spot?

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[frankr]

Those pins have a tapered head on the inner end. That tapered head seats in an o-ring. If the o-ring has some sort of deformity, it can affect how far the spring pushes the pin outward.

As said the vent is one-way. It admits air as fuel is consumed, but does not let air out (or let fuel slop out). So pressure increase in the sun is normal. Your carburetor float valve is supposed to be able to hold against that pressure. Of course you can use the Redneck cure and loosen the cap.

[jmar]

So I’ll take that as a yes to replace the o-ring on one side and a no to opening the tank cap at each stop since i have no leakage problem at the motor, only the tank. And once I fix the tank leak I can leave the cap closed while fishing.

[billw]

As usual, nice job, Art. Thanks for that link!

Long live American manufacturing!

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