Fuel tank breather?

[Mouldy]

Funny thing happened on the way to Portaferry...
Been cruising and flat out mixed for about 2 hours - had a 2 hr break, then set of again - 10 mins later, eased off the throttle and the revs died and the engine stopped.
Fuel bulb was soft, pumped it up, wouldn't start. Unscrewed fuel cap, plenty of fuel. Re-primed fuel bulb and it started 1st go and ran fine for the rest of the weekend approx 4hrs including one non-stop 35 mile run.

I was thinking an air bubble in the fuel line (about 70 litres in the 100l tank at the time).
Can you get a partial vacuum in the tank preventing fuel flow?
Should the fuel tank have a breather? What stops petrol evaporating when a tank breather is fitted?

[Nos4r2]

It'll have a breather of some kind somewhere-and yes, a partial vacuum will stop fuel flow. If you're running carbs then it can damage fuel pump diaphragms too.

[BogMonster]

Have a look at this thread here

I had breather problems of a different sort, but when I did get it out I found the breather hose had been kinked quite badly. As it happens it wasn't, but it could easily have caused fuel starvation had the kink been a bit worse. There are photos of a couple of different breather exit arrangements in that thread.

[stingraymax]

I use a breather but I have the tank in my console but when I topped it off The fuel came thru the breather, so I installed a Fuel surge protector from attwood that I got from ebay, and never had a problem since.

[Simon B]

Check any of your fuel line connections, if you've been running flat out and it was the breather you may not have managed two hours, moreover, it may have been vibration during the 2 hours that shook a connector loose enough for it to pass air.

Likewise it could also suck in water as the fuel system is at negative pressure so see if any in line filters have water in them.