Pressure in gas tank

[Basie]

Hi all

I have 70 series 4500 EFI model. Gas was shunted from main tank to aftermarket extra tank and out the road thruogh extra tank breather when driving along. I installed valve between tanks to stop this, now pressure build-up in main tank and venting gas and fumes through breather on top of main tank with smell of gas when driving with windows open. When engine is running there is a high flow of vapour/air out of this breather. On other local models there is a vapour valve, but this breather goes on out of a long line on to the railings as high as the cab, but still venting liquid gas and fumes.

Is this high pressure and vapour venting normal and will a vapour valve sort out the problem

THX 9 great forum by the way

 

[roscoFJ73]

There is no easy answer to this without seeing it,you would at least need to show us a diagram of how the fuel lines are arranged. I would contact the company that sold the aux tank.

Fuel spilling out has a serious fire risk

 

[Basie]

Hi

I have a diagram of my tank set-up

1 aux tank
2. Main tank
3. fuel pump for rapid transfer needed when cosnumption high and gravity to slow
4. Electric cutt off valve. Otherwise fuel woud flow to aux tank even through valves of pump and spill throufg aux tank vents
5. Aux tabk filler
6. Main tank filler
7. To engine ( there is also return from EFI system to main tank
8. breather to filler and atmosphere
9 breather to atmosphere. About 5 feet above tank level will vent stream of vapour while engine is running and some fuel as well. Used to have a 'vapour valve', but have been removed because of poressure build -up


My problem is this high volume venting normal and how can I prevent fuel and the smells and the obvious risk. I have isolated the aux tank with this valve to prevent spilling from aux tank

Thx

 

[roscoFJ73]

Does the fuel line from the aux go to the bottom of the main tank or bad drawing?
Do you know if the aux tank is overfilling the main tank?
Was the breather (9) there before ,or was it something you added/extended?

You might be better off to have 2 separate tanks that go straight to the engine .
You would then need a fuel return to each tank

 

[Basie]

Hi Rosco

No, the drawing is good ( I Think ) . The aux line does go into the lower part of the main tank, but overfilling from the aux tank not the problem. I isolated them from each other. But there is still pressure build up in the main tank and it vents through the vent nr 9.

The vent is on a factory fitting on top of the tank, but seems to go through a vapour valve or something in the original, but has been changed during the installation of the extra tank that was done at the same time as a double cab conversion Two kids, you know. Is the high venting flows normal and how do you contain the fuel vapour and even drops from venting.

Thx