fuel demand valve

Recently installed a new portable gas tank in my boat with the EPA regulated cap. After a period of time I realized that the tank pressure had pushed over a gallon of gas through the carb and on the ground. Installing a FDV and I understand the concept but pressure is still going to build in the tank. I read somewhere that the new caps will vent internal pressure once it reaches 5 pounds per square inch. Does anyone know if this is accurate ? Loosening the cap is defeating the purpose and gets messy while driving.

I started a similar discussion recently .. https://www.tinboats.net/forum/viewtopic.php?f=3&t=39965..

I added my FDV after doing some reading and talking to my treasured mechanic of 20 years.

I've had the boat out twice and had no issues with it starting or running. My tank did expand big time the first time after I installed the FDV, but it was nearly empty. Loosening the cap took care of that.

Each of the two times that I took her out, I loosened the cap BEFORE I got on the road, I immediately closed it.....and then did that again after I ran the boat.

The whole EPA rule makes little sense if we are going to have to loosen the cap from time to time. Whatever fumes that build up in the newer, thicker tanks will still be released to the atmosphere.

Just an example of another failed government program that accomplishes nothing but costs industry and ultimately, we, the consumers, tons more money.

richg99

Those in favor of of liberal or progressive use of goverment regulations to control us in a socialistic way have made it so politically incorrect that you can't even talk about it on websites. They and have made it uncomfortable even to talk in public to the point they call you names or biggot if you do not suport the lefts view. They made it toxic so you and I won't discuss it. Liberal presidents appoint people that use liberal or a lot of government regulations. Conservatives use conservative or less regulations. This may only seem minor with a gas tank issue but the off road community's land closures was only a warm up to the water ways they want closed to power boats. Some rivers like the one I grew up on, the Mullica River in South Jersey is entirely no wake zone now. Florida's inland waterways are no wake for miles because of the environmentalist appointed by Democrates. If you want a good deal on a boat then go to Florida. People can't get rid of them fast enough because you have to go slow. Vote wisely.

Rich, I read your thread :
https://www.tinboats.net/forum/viewtopic.php?f=3&t=39965.

and this one on the Whaler site:
https://continuouswave.com/ubb/Forum1/HTML/021090.html

The old Italian woman in the movie was correct "This is a Catcha 22" :shock:

Now I understand why some people get their gun, their dog and go into the mountains ... never to be seen again !

fishmonger...Well, one interesting thing in the 2011 BW post was the assumption that one was to leave the tank in the "partially open" 'position when running. I didn't do that. My engine ran OK, but I didn't run it for very long. Sounds like it will make more sense to leave it cranked open one turn.

That way, no vacuum will build up. Might be, since I am still using my old hose and bulb, that I have enough leakage to prevent a full vacuum condition.

Now, opening the cap a bit sounds a lot more dangerous than the old system of a tiny twist cap fitted on top of the regular cap. It also would, I think, let fumes exhaust to the atmosphere, which is what all of these new procedures and equipment were trying to prevent.

You are correct. Catch 22

richg99

Pressure will still swell the tank. And correct the cap is still supposed to vent once pressure builds to >5 lbs. I am also running the FDV and have not had any flooding issues since. Although I didn't have any before either.
One thing I do is disconnect the fuel line from the motor while flushing. Not only does that run all the gas out of the carbs, but then if there was a pressure increase, it wouldn't push gas into the motor.



2015 Tracker Grizzly 1448 MVX
1996 Evinrude 25hp 3 cylinder looper

LOL this is where I just laugh at the regulations put in place by our government. Let's mandate ventless fuel cans and ventless portable fuel tanks for boats. That way, we'll clear up the air from evaporative hydrocarbons. But then the carb overflows because of the excess fuel pressure and leaks 5 gallons of gas out of the motor, onto the floor and it evaporates. Or in the case of the ventless fuel cans, you dump 1/2 of the gasoline you're trying to pour into your lawn mower onto the ground. Both are results of an "excellent" thought process of our bureaucratic idiots that we placed into office.

As far as tank swelling, I've found that the el cheapo' cans you get at wal-mart, dicks, Academy, bass pro, etc (Sierra, Moeller) are thinner material and they'll swell up about twice their normal size. I bought a Yamaha tank for mine and it doesn't swell much (3 gal) but its' a LOT heavier (thicker plastic).

I wonder, though, if the pressure of a fuel tank that is holding, say, less than a gallon of fuel could aid in it's combustion if a fire were to break out on board? I.E. bomb? Don't know enough about fuel and how much pressure has to be present for it to become explosive....

At work we also sell accessories. We can't get the vented fuel cans fast enough to keep up with demand....which reminds me I need to pick up a yellow one for the lawn mower.