Fuel Filler

[Poida]

My fuel filler is at the transom and goes straight down into the tank.

When filling it creates blowbacks and keeps clicking off the bowser nozzle.

I assume it is because the pipe from the filling cap goes almost to the bottom of the tank and therefore doesn't allow the fuel to flow into the tank fast enough as the level in the pipe doesn't go down until yhe tank level rises.

Is the filling pipe fitted so it goes to the bottom of the tank for any reason, or is it more likely that the person who fitted it was too lazy to cut it.

If the pipe level was just below the top level of the tank it would allow the pressure on top of the fuel to escape and prevent blowbacks.

The only reason of sorts that I can figure you would need the filling pipe to go to the bottom would be to reduce the fumes on top of the fuel in the fuel tank that would vent through the filler creating a fire hazard.

It is petrol or gas as some non english speaking countries call it.

Poida

[FAST FRED]

Most likely the problem is a lack of , or plugged tank vent.

It is crappy practice NOT to vent the tank as filling is a real pain (as you found out).

Look for a vent from the upper part of the tank and be sure it is clear.

FF

[tom28571]

It's not likely that the filler pipe goes to the bottom of the tank. If it did, the movement of fuel in the tank could very easily create enough pressure to slosh fuel back out of the tank through the filler pipe. The pipe could have some bends that create back pressure or, as said, the vent could be plugged.

[Poida]

Thanks Tom and Fred, I'll check for a vent somewhere on the tank. There is no bends Tom as I use a dipstick to check the fuel level and the stick goes straight to the bottom.

Thanks again

Poida

[PAR]

Yep, the tank vent line maybe partially or completely blocked, which is a common problem. Often a screen is used at the vent, that gets plugged with dirt and ozone, which is enough to cause the problem you're experiencing. Check the line isn't kinked or making a sharp bend around something, that may constrict it's inside diameter. Mud wasps like to build homes inside these hoses when the boat is idle for a while. Remove the hose and run a coat hanger or other suitably long, thin piece of wire through the hose to insure nothing is living inside it. Do this with the hose removed, so junk doesn't fall into the tank.

Some times the vent hose is just too small in diameter, for the rate of fuel delivery coming from the nozzle. I've had cars that did this and had to use less then "full" squeeze on the nozzle to get it to take fuel. Increasing the diameter of the vent line and vent cover can relieve this problem.

[Poida]

Thanks for all your help but I just examined the fuel tank and it doesn't have a breather. The problem would probably come from the turbulance from the fuel hitting a reduced diameter where the filling hose attaches to the flange on the tank.

I might return to the idea that I had before seeking advice here, and that was to get a steel fuel jerry can and weld a 6mm (1/4") valve on the bottom and let that fill the boat at a slower rate without the blowback.

I don't feel like fitting a breather as I would have to take the tank out and degass it before working on it. I might wait until I need to remove the tank for another reason and kill two birds with one stone.

Poida

[Digby]

G'day,
not trying to steal your thread Poida, but thought I'd ad this as I have a question about blowback aswell. I have a 120L tank mounted up the front of the boat with about 1 metre of 2" hose going to a fuel filler. There is one line going to the engine and one breather line that goes above the control panel and vents (isnt blocked)

On a lot of cars I have noticed that there is an additional breather that is piped back into the filler neck to prevent blowback. I've taken my boat to a mechanic where I live and they say you dont need the additional breather going to the filler neck and the ones they sell dont have an additional port to pipe a breather to.
At the moment it takes forever to fill as the breather isnt getting enough air back up the filler pipe. The pipe does run horizontally (roughly) and into the top of the tank, which could be another cause of the blowback as its trying to push the fuel thru the pipe and not enough air is able to flow back.

Any suggestions?

Thanks

[Poida]

Hi Digby, I can't help you as I am still trying to sort out my owm blowback problem, which has been put on the backburner because I am rebuilding some of my trailer.

However what I am going to try is running a plastic tube down the inside of the filler tube to just under the level of the top of the tank to vent the air.

It should have the same effect as what you are talking about.

See ya

Poida

[riggertroy]

Just a suggestion - if possible fit a smaller line inside the filling line as a breather - if the filling pipe is straight you could even try making a funnel with a piece of pipe fitted that will extend to the just below the top of the tank and that could act as a breather to prevent blow back

[Poida]

Thanks riggertroy, but I believe if you read my previous thread that is what I intended to do?

[MommyDearest]

Glad to have found this forum and thread.

DS just purchased a '94 Stratos 2250 w/cuddy and 225 Yamaha OB. The onboard gas tank is 96 gals. On prepping and testing the boat he's just been dumping in 12 gals gas at a time. To test why/if the console fuel guage was working, he attempted to pump at the gas station directly into the fuel filler onboard. Gas would not go in and actually came out the adjacent vent. Naturally, he stopped!

Question: Since the fuel spit back thru the vent, my thought is that the vent line is not blocked -- BUT, we're wondering if the tank is air-bound? Is that possible? I asked him if the tank was already full and that's why it was spilling back - he said that no, he's pretty sure the tank was empty - because it sounded "hollow".

The location of the filler cap is on the ledge of the walk-around on the starboard side adjacent to the captains chair. The vent is next to it but out the side of the boat.

Any thoughts/suggestions. He's 21 and this is his first boat and very eager to get it in the water for the summer!

[Poida]

Welcome to the forum Mommy Dearest.

Mommy Dearest?? Oh well never mind.

I haven't got back to the fuel filling problem yet as I am in the proccess of replacing the suspension on my trailer. Held up unfortunately because I can't get a replacement set of springs for two months.

They reckon bad luck comes in threes, I'm currently up to 573 and still climbing.

Well back to your problem, it seems that the vent may well come out of the filler pipe somehow as I can't see it coming out of the vent if the tank was vented.

From replies I have had it seems like it's a common problem.

I am going to try running a hose down the filler tube when I next fill it. This I think well make the fuel run down the outside of the tube and break the vortex (the swirling action of the fuel) which I think is causing the back flow.

Gotta get my damn springs first.

Poida

[Digby]

Hey Poida,
I've done the same as you and put the boat on a dozen tyres in the front yard while i give the trailer a full birthday.
Just reading back thru your posts, how hard would it be to leave that filler in place and install a new one on your tank that doesnt have a pipe that goes all the way to the bottom? I know the hot work side of it is a pain, but if can drain the fuel and fill it with water it shouldnt be a prob. That way you could block off the old one at the tank and swing the filler pipe over to the new inlet and it should fill ok like a jerry can.

Just a thought.

Digby

[MommyDearest]

LOL yea, MommyDearest is an inside family joke -

Thanks for the input - feel your pain on the trailer - sending positive vibes!
Bought the boat too late in the season to find slip space, so DS's trailer work will have to wait til another time.

I've printed out your suggestion and will show it to him tonight.
At this point he'll give anything a try!

[MommyDearest]

Well, he used an air-hose to blow back (after disconnecting from tank) and no clog, so the vent was properly working - and all seems fine now - must have been some fluke (well, not literally of course - as fluke season just opened LOL!!)