How much air in a fuel line is normal?

[chal]

I've posted several fuel line questions lately so apologies for being repetitive. Anyway, to recap, I recently replaced an old fuel tank with bottom fuel line attachment point to a new one with a syphon and have had endless problems with air getting into it. After various attempts to solve the problem, I have now reached a point where there is an unbroken line from tank to filter and the line is translucent (proper fuel line expensively sourced in USA) so I can see what is going on.

There are no little bubbles in the line to show a leak at the filter connection, nor can I find any trace of fuel to indicate a leak anywhere in the line between the tank and the HP pump. Nonetheless, there is now an air bubble in the line, about 3 or 4 cm long; it's naturally at the highest point, ie where it connects to the tank. It's a sailing boat so we don't generally run the engine all that long, but the bubble seems to get bigger quite slowly and not make any difference to how the engine runs.

Is this something I should worry about, or something that would tend to accumulate over time that I simply wouldn't see if I had stuck to black fuel line?

 

[NormanS]

If the bubble is getting bigger, no matter how slowly, it will eventually cause you maximum embarrassment at the most inconvenient time.

 

[zambant]

You need to get it sorted - you should not have air bubbles in your fuel lines.

I agree with Norman " it will eventually cause you maximum embarrassment at the most inconvenient time"

 

[chal]

Many thanks to both, I'll take another look at the cursed thing. I think it's getting close to the point where I drill a hole in the side of the tank!

 

[KellysEye]

> Nonetheless, there is now an air bubble in the line, about 3 or 4 cm long; it's naturally at the highest point, ie where it connects to the tank. It's a sailing boat so we don't generally run the engine all that long, but the bubble seems to get bigger quite slowly and not make any difference to how the engine runs.

What I don't understand is if there is a large bubble in the fuel line how is fuel getting to the engine past the bubble?

 

[Rivers & creeks]

Air getting in via the filter housing and making its way upwards?

 

[cliff]

Air getting in via the filter housing and making its way upwards?

Now funny you should say that. Had a situation recently of air in a fuel line - could not find the leak - double clipped connections - changed to crimped etc etc - still a little leak - rigged a couple of connectors for the extreme ends of the piping and applied 5 PSI and checked with soap solution - filter housing rubber seals leaking ever so slightly - changed filter (again) and double checked the seals - small piece of grit stuck beneath the seal was enough to allow the small leak.

 

[Searush]

How much air in a fuel line is normal?

Sorry, but the answer has to be NONE whatsoever.