Petrol tank breather?

[alextangent]

There's no breather on my 93 petrol tank. How does this work; presumably the filler cap isn't airtight?

 

Alex McDonald

A loud 1700 SS

[millsn]

Normally the tank breathes via a tee in the filler pipe so you wouldn't see this on a bare tank.

[Dee Pee]

On my '95 the breather is adjacent to the feed take off on the top of the tank but has been sealed off with a piece of hose and a circlip. tHIS IS PRESUMABLY WHY THE TANK IS SO SLOW TO FILL AS IT VENTS through the filler cap.

 

 

[alextangent]

I called a company to buy a new swish filler cap, and they told me that as it was a sealed type, and to check the tank as it would cause problems if there was no breather due to negative pressure in the tank.

 

So I've got the tank out and there's no breather at all on mine, just the fuel inlet with a big rubber tube from the filler cap and the fuel pipe outlet on the other side. I'm assuming that the tank must breath through the filler cap 🤔 🤔

 

Alex McDonald

A loud 1700 SS

[philwaters]

If you are on carbs then you can drill a 2mm hole in an flush type filler cab - under the flap is a good place, out of sight...

 

Phil Waters

[alextangent]

Yep, carbs with currently mechanical but going to electric pump. You know, I like simple solutions, and that one's brilliant

 

Alex McDonald

A loud 1700 SS

[Andy A]

Take a look at the fuel gauge sender unit. I think you'll find a little hole in that.

 

[alextangent]

That's true; but it's under the cork gasket, so it can't provide that much breathing (plus it leaks!). Seems an odd place for it 🤔

 

Alex McDonald

A loud 1700 SS