Aux tank problem: spilling fuel

[Dirk16]

Hi there,
I'm from Germany and I do have a FJ Cruiser here from a customer which I have fitted with an aux tank a while ago. It is filled by a Y-turnoff, when the main tank is full. Works well so far.

After the usual horror stories with the pressure test I finally managed to seal the system properly.
Nevertheless, the customer's getting the christmas tree after a while, AND:

There's fuel spilling out of the, I guess, vent hose from the carbon canister.

What I don't understand: the excess fuel should flow back via the Y-piece into the aux tank. There's only one way for fuel spilling: the (bigger) vent line from the carbon canister.

I just made another system seal test and blew everything up to 0.3 bars, which is the official testing pressure here.
Ok. But when I released the pressure, I heard a snoring sound accompanied by gentle vibrations in the filling hose close to the tank.

Is there a drawback valve in the filling hose?? This would explain the spilling, but in the scetches I have there is nothing, except a cut-off valve and a roll-over valve in the line to the canister.


I don't understand why there is fuel coming out of the canister line...

Is is right that the "bleeding line" is where the excess air from the main tank goes through while filling it? Or is the main air leaving through this canister line?


Cheers,
Dirk

 

[Dirk16]

Hi,
two more pics: one is another scheme from the FJ tank system, the other is appr. what I've made.

So this is the riddle...how does the fuel get out of the canister filler line, whis is normally only the inlet for the canister regeneration?

Cheers,
Dirk

 

[Dirk16]

Is the following right:

-the canister system is always open except for the pressure test?
-so when overfilling the main tank by pumping (it's a rather strong pump, but a lot less than the fuel station pump), the pressed out air is going...where? It should go through the bleeding pipe and from there back into the aux tank.
-excess fuel should just flow back into the filling hose and into the aux tank...but it seems it doesn't

Cheers,
Dirk

 

[Dirk16]

Ah, sorry, forgot to say: both bleeding line and "vent aux" are tightly sealed by the fuel cap, because else the pressure test wouldn't work. They "meet" just below the cap, my aux vent is welded into the metal.

Dirk

 

[Dirk16]

Me again...talking with myself...

Would it be possible to install a back pressure valve in the canister line or would this cause too high pressure in the tank system when the fuel is evaporating?

Dirk

 

[T-ridecruiser]

Anyone have any help for dirk?

 

[Dirk16]

I think I have solved it with a new inlet into the tank filler instead directly into the tank. No spilling when pumping. No christmas tree until now, but this might just take some days...

Cheers,
Dirk

 

[Mtbcoach]

Well done...

 

[Dirk16]

This is how the filling hose looks like now:



Dirk

 

[Mr45]

any updates on this Dirk?
I'm of no help for you, but I'd like to see some pictures of your work.

 

[Dirk16]

Havn't heard anything negative from the owner yet, so I suspect it's working like desired.
Tha last failure notification was then probably from fuel spilling into the purge valve or carbon filter canister, I assume, so the system got soaked and drowned. Til now, I have no idea of HOW the fuel got there, but the only change I made was filling the main tank from the standard filling hose (see above) and not directly in the tank body with an attached filling inlet.
The only picture I have it the one above, it's the filling hose with the inserted T-piece. If the tank is full, the fuel does no longer flow into the tank but backwards to a welded Y-piece in the steel inlet tube and then back into the aux tank.