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Omc gas tank leak only when cap closed tight

B

Bobos

New member
I have two omc tanks (early 80s) that leak from the tank fuel outlet when the cap is closed. If the cap is turned to the first stop the gas stops running. These are single line tanks btw.

Tank connector was rebuilt twice with new orings and front pin seal to no avail.

If the tanks are meant to be sealed then no air gets in and out. Leaving the tank in the sun the tank can build pressure so I don’t see how it’s getting air in to allow the fuel to flow

Also installed new gaskets in cap and under outlet

I’m at my wits end. The only thing I can see is that there is a rubber valve under the outlet that according to Crowley is called a valve assembly and it’s parts 26 27 and 17. I don’t know what it does other than if the cap does not vent then I wonder if this is a vent of some kind

Feedback appreciated.

TIA
 
Connecting the hose pushes the pins in, which allows fuel to flow, and vents the tank. I'm really not 100% sure, but I think that rubber valve is a one-way valve.
 
fdrgator said:
Connecting the hose pushes the pins in, which allows fuel to flow, and vents the tank. I'm really not 100% sure, but I think that rubber valve is a one-way valve.
Click to expand...

I didn't say that too clearly, did I?
Should say I'm really not 100% sure how it is constructed, but I think that rubber valve is a one-way valve to prevent emission of fuel and fuel vapors into the environment. It's the Law, y'know.
 
Since posting this I was told that the valve is a one way valve and only opens when significant pressure builds up in the tank. So I do have pressure and I suspect that it’s working correctly.

Going to take out the plugs again to see if I have the o rings in the right spot.
 
This valve is not perfect. Perhaps the little pin is damaged, tiny O-ring not sealing the best. Best to keep tanks in shaded area when hose is disconnected. If it vents into the air it's not a huge concern.
 
For instance, there are nearly 93,000 commercial airline flights in the world every day, that doesn't include private flights and military. I really doubt that a few thousand fuel tanks venting into the air will make a huge difference.
 
Issue solved. O rings were not seated completely on the shoulder allowing the head of the pin to pass the oring and not seal properly .

All tanks work good as new
 
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