gas tank check valve?

[maxx rpm]

I have a 15 gallon underfloor gas tank. I seem to have an issue with gas draining back into the tank. Have replaced the bulb/hose that connects from the splashwell fitting to the motor, and no different results. I had the floor off a couple years ago, and i didnt see any evidence of the hose being bad. So my question: Is there a check valve on the tank? Or is just the primer bulb supposed to keep the gas up? Not interested in any guesses, just first hand experience with this.

Thanks! Mike..

[Esox_Magnum]

If the bulb is good then bad line from the tank. Your getting air in someplace.

[maxx rpm]

So you dont think there is any check valve on the tank fitting?

[Esox_Magnum]

Can't say for sure on your boat but never seen one in any I have or have had.

Dumb question but are you sure the flow on the current bulb is correct?? I have seen bulbs bad off the shelf to.

[morepower02]

Alot of boats will have a check valve on the tank pickup. The only way to know for sure is to access the pickup and check.

[maxx rpm]

I tried 3 different types of bulbs, all dont seem to hold pressure well. Good point though, just cause somethings new dont make it good! Really dont like your hose idea--just because it is under the floor!!! Dang, well might have to take up the floor i guess. Thanks for the replies though.

[CAMAN]

It's actually called an Anti-siphon valve and yes they can go bad. Should be mounted on the tank.

[Esox_Magnum]

So is this anti siphen on or in the pick up tubes?? Not exactly sure what these look like, maybe have seen it and didn't understand what I was looking at....

[CAMAN]

It connects to the outlet of the tank.

[morepower02]

It's a anti siphon check on the outlet of the tank pickup. EDIT. You posted the pic while I was typing.

[Esox_Magnum]

Ok learned something new then, always thought it was just a connection...

[Bigtom]

Is that just a standard ball check valve? Could you unhook the primer bulb and try to use compressed air to see if you can blow in the fuel tank? Might be worth a try to see if the valve is working or not. I am not sure if it will work or not.

[CAMAN]

You may be able to try that but it won't show a small leak. The best test is to remove it and install a section of clear tubing 1-2 feet long onto the barbed side of it. Hang it vertically and fill tubing with water. If you have any leak, even a very slow drip the valve should be replaced, or at the very least cleaned and tested again, it could have just had some junk from the tank jammed in it.

Edit: on second thought, using compressed air sounds VERY dangerous and probably shouldn't be done. For one the fuel lines aren't rated for high pressure, and secondly pressurizing a fuel tank could cause a huge problem.

[Bigtom]

yeah I never thought of that(pressurizing a fuel tank)

[maxx rpm]

I have seen that type valve when trying to check on this, and they made it sound like it was just a fitting. Doesnt make sense to me with such a rise in the hose to not have something to keep the gas up there. I now have another project!! But sounds like might be giong in the right direction now. Great replies, and pic too! A little disappointed no one suggested blowing in the end of the hose(yes, i can imagine what would happen). A little excited, did get the boat up from the back--10" deep rut to fix now, and did get it started. Some decent weather, and open water time for me! Thanks guys.

[maxx rpm]

So, took the floor up, and had that fitting, but was either just a fitting or the ball went back down the tank. So i got one with the check ball, and it did fire right up and seems to be better. Have to test it out on the lake though, hopefully soon!!