Expanding Fuel

[shakey55]

Good afternoon to all. 

I have a 2000 model Seafarer V-Sea with an under floor fuel tank (80L)

Last week I was going to sea with a mate and when we pulled up for fuel he said I’ll get this one.  He is my normal deckie and we share expenses. 

Enough of that, I think (I’m sure) he put to much fuel in. 

We headed to Gymea ramp the I got a phone call that terminated the day, no fishing.

The last couple of days have been hot, with today touching 40+

The wife tells me she can smell petrol near the boat. 

I go to investigate and yes there is fuel dripping out of the centre/lower bung holes. 

I take cover off inspect the bilge area and yes petrol dripping from joins in pipe that leads from fuel tank to filler. 

I lean over the back of boat, undo fuel cap, remove and a at least a good two litres of fuel erupts/gushes out. 

I know the reason and understand fuel expanding etc etc, but would this be considered normal ?

I ask this question only because I thought there would’ve / should’ve been a release valve or something to overcome this happening. 

Thoughts, etc (Please)

[oldtown]

Always fill your vessel or vehicles on a cold day. If fuel expands on hot days then the provider sells less for the price.

[Fab1]

6 minutes ago, oldtown said:

Always fill your vessel or vehicles on a cold day. If fuel expands on hot days then the provider sells less for the price.

That's it!!! I'm waiting until winter to fill my car to get to work next week.

[jeffb5.8]

I can smell fuel on hot days when I have a full tank, but it’s from the fuel vent.

do you have a working vent?

[Fab1]

3 minutes ago, Fab1 said:

That's it!!! I'm waiting until winter to fill my car to get to work next week.

In all seriousness all tanks must have a breather/valve to prevent such things from happening.If he filled it to the brim and these are not working as they should(Clear/opening closing) what you experienced will occur.

Same thing with portable tanks.Fill them full and leave the breather slightly unscrewed and fuel will expand and leak out the breahet in hot weather.My tank blows up like a ballon in the stinking heat in the garage with a closed breather and it's never fully full.

[shakey55]

On 19/01/2018 at 7:39 PM, jeffb5.8 said:

I can smell fuel on hot days when I have a full tank, but it’s from the fuel vent.

do you have a working vent?

Yes they both appear to be okay.  Going to double check today

[rickmarlin62]

start the motor on the hose and use a bit...no seriously..i would say hes over filled so you will just have to deal with it or undo fuel line at motor and drain some into drum..rick

[sydney south]

You should not have had the fuel gush out of the filler if it was higher than you vent/breather. If this occurred it is suggesting that you have a blockage or kink in your breather hose.

I have a deck filled under floor tank that also has a breather that is lower than the deck fill. It is normal that there will be fuel discharge from the breather on a hot day if the tank is filled to capacity.

Also, make sure that your breather and breather hose to the tank is clear, so that your motor works efficiently, so as not to create a vacuum in your fuel system.

[zmk1962]

@shakey55 as others have said, the breather is there to vent the tank... from what you describe I think you may have a combination of issues:

1) vent is blocked: make sure that you do not have a kink or flattening of the breather hose from the tank to the deck vent (mine looked ok but when I actually took it out and checked I found that it had flattened shut at one section but looked ok from the normal viewing angle).

2) breather pickup location: you could have a case of the breather pickup being at the stern end of the tank and a combination of filling the tank to capacity and tilting the boat up at the bow may have positioned the liquid fuel across the breather pickup with the vapour further up in the tank.

As the vapour expands it forces liquid fuel out of the breather but since you are not seeing that I suspect the breather hose is kinked and the extra pressure is forcing the fuel out of the joins as you described.  Also once you opened the filler cap, the fuel sitting across the filler was expelled.  Which again suggests your vent hose is kinked or blocked.

This "vapour lock" can be a common problem with long subfloor tanks with the breather pickup at the back. (PS - A friend of mine had problems filling his tank to capacity, unless he took the trailer off the towball and tilted it forward. this could be another manifestation of this problem. You may also at times experience the motor becoming sluggish or bogging down - if the breather pickup is blocked by fuel resulting in fuel tank vacuum restricting fuel flow to the running motor.)

So I suggest check your breather hose first. Once you are sure there is no vent blockage, perhaps try tilting the rig forward and see if you get vapour from the vent to confirm this is your tank design. 

Note: I'm speaking from experience here as my original 200L tank in the Haines had the same issue. When I eventually had the tank replaced, I had the tank manufactured with the breather pickup at the front of the tank as shown in the last sketch. Most boats ride stern heavy, and sit tilted back on trailers so the breather pickup at the front works better.

 

21 hours ago, rickmarlin62 said:

undo fuel line at motor and drain some into drum..rick

You may need to get rid of some fuel to check your breather hose, as @rickmarlin62 said undo the fuel line at the motor, or if you have a push on fuel connector (usually female) you can purchase the corresponding male connector, rig it to about 1m of fuel line then any time you want to siphon fuel out (lawn mower etc) just connect this up to the fuel supply and use the bulb to start the siphon action. 

Cheers

Zoran