Air pockets in fuel fill?

politby

Stopped for a fill up last week and the starboard tank (which only had about 20 gallons in it) only took about 10 gal. before the pump shut off. There was fuel all the way up the pipe to the fill cap. 

Anyone experienced this? Air pocket?

212rowboat

hung float.

politby

Okay. You lost me there. I assume you are referring to the fuel sender's float. Why would it be in a position to block the fuel fill?

212rowboat

I'm sorry, I was mobile when I typed that- more detailed:

I'd guess the float is hung up, and reading less fuel than is actually present- hence, it is full, but reading less.. are you certain the tank is at half capacity?

politby

Ah. No that's not it, I have fuel flow meters so I know exactly how much is left in each tank. 

A few hours later it looked like the fuel fill pipe was cleared but I haven't tried filling up again.

212rowboat

my next guess, then, would be an obstructed vent disallowing filling.. it would come right up the fill tube as if it were full...... were you filling it pretty quickly or trickling it in?

politby

Maybe that was it. This particular fuel pump is pretty fast so maybe it just overloaded the fill line.

Lifes Good

your fuel line had a vapor lock. kinda common. check your fuel line in the boat. it more than likely bends down and then back up to the tank. when you fill fast the air in the line blocks the flow. start really slow and allow the fuel to gain flow. then you can fill faster. this is usually the reason during filling that fuel blows back out and makes huge mess... hence cover the fuel with an absorbent while filling. that helps keep the mess down.

politby

Well the boat was not used for 3 weeks while we were away. Yesterday I tried filling up and the problem was the same. Had to switch to run both engines off the port tank.

Tried blowing into the fill port but to no avail. Will try feeding a flexible PVC pipe into the fill to see if I can evacuate any air.

Is there an air bleed line or overfill vent that might be blocked?

Lifes Good

did you check the line from in side the boat to be sure it has a smooth angle to the tank? the line may have been strapped and a strap may have given way allowing the line to sag...?

politby

Lifes Good said:

did you check the line from in side the boat to be sure it has a smooth angle to the tank? the line may have been strapped and a strap may have given way allowing the line to sag...?

Will have a look tomorrow. Thanks for the tip.