Fuel Caps: vented vs non-vented?

[tpb]

I was looking for a replacement fuel cap for my 110, and there seems to be a choice between a vented fuel cap and a non-vented fuel cap. Now on to the questions!

1) Are caps vented to allow for expansion of fumes during warm weather?

2) Is venting required for a diesel?

3) Will venting allow water into the tank during severe rain or when submerged?

4) Under what conditions would you use one versus the other?

Thanks!

[mmgemini]

I was looking for a replacement fuel cap for my 110, and there seems to be a choice between a vented fuel cap and a non-vented fuel cap. Now on to the questions!

1) Are caps vented to allow for expansion of fumes during warm weather?

2) Is venting required for a diesel?

3) Will venting allow water into the tank during severe rain or when submerged?

4) Under what conditions would you use one versus the other?

Thanks!

1 Black are vented, grey are non vented. Wait a second though. A few years ago some black caps came non vented. They are vented to allow the diesel to get out of the tank, otherwise you'd have a vaccum in the tank.

2 Yes

3 No

4. If you have a vented tank opposed to a vented cap you can use a non vented cap.

Me........Well I'd fit a vented cap every time.

mike FOAK

I can cause trouble in an empty house !!!

[FridgeFreezer]

I'd fit a vent to the tank and a sealed cap to keep water out when wading. But that may be more effort than you want/need.

[Les Henson]

A lot of modern day cars have a seperate breather with a vapour trap in. You could source one from a scrappy (put a 'T' connection in the balance pipe), and then fit a sealed cap.

Les.

[will_warne]

1 Black are vented, grey are non vented. Wait a second though. A few years ago some black caps came non vented. They are vented to allow the diesel to get out of the tank, otherwise you'd have a vaccum in the tank.

2 Yes

3 No

4. If you have a vented tank opposed to a vented cap you can use a non vented cap.

Me........Well I'd fit a vented cap every time.

mike FOAK

I can cause trouble in an empty house !!!

Whatever fuel you use you need to vent the tank so air can get in to replace the fuel being used. If you don't you create a partial vaccum in the tank and the engine will stall. If you fit a non vented cap then you need to fit an external breather with a roll over valve. Personally I don't like the standard LR setup very much so mine's gone in the bin and I've done something very simerlar to Hybrid from Hell (see his fuel cap thread in the tech archive). This gives a superb seal to the tank to ensure water won't get in during wading.