Air Pockets in Fuel Line - Normal?

[Jacalore]

Installed clear 3/8" fuel line from inline fuel filter to fuel pump intake. There are large pockets of air present in the line. After the engine warms up, and starts to drop to idle rpm, it quits. Can only start it again after throttle choke and will run for a few seconds at high rpm then die. Air pockets move around but never move thru. Removed inline fuel filter and ran straight from tank to fuel pump, still see large air pockets moving around in the clear fuel line. Do I have a leak in the tank? Or are these air pockets normal? Thanks.

 

[MRS]

Re: Air Pockets in Fuel Line - Normal?

Do you have a clear line running from fuel pump to carb? If you do and is dumping fuel into carb you fuel pump is bad.

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

New fuel pump installed last week.

 

[MRS]

Re: Air Pockets in Fuel Line - Normal?

Ummm, sounds like you are leaking air some where sorry could not help maybe someone will be along shortly that can help. Do you have two tanks and a three way value or just one tank?

 

[NYBo]

Re: Air Pockets in Fuel Line - Normal?

The tank HAS to have a "leak" (vent) or fuel would stop flowing. Check all your fittings from the tank to the fuel filter for air leaks.

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

Ummm, sounds like you are leaking air some where sorry could not help maybe someone will be along shortly that can help. Do you have two tanks and a three way value or just one tank?

Thanks. Just the one tank. Is it normal to have air in the fuel lines?

 

[MRS]

Re: Air Pockets in Fuel Line - Normal?

Thanks. Just the one tank. Is it normal to have air in the fuel lines?

No....

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

So, how do I test to find the leak? It's an aluminum tank, buried below the floor. I can get at the fittings thru an 8" inspection plate. Possible to pressurize the system somehow?

 

[MRS]

Re: Air Pockets in Fuel Line - Normal?

Can you smell fuel any where in the boat?

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

Yes, actually I can... whenever I take the cover off, I smell gas...
But the tank does not drain... not noticeably anyway

 

[MRS]

Re: Air Pockets in Fuel Line - Normal?

Might want to check and change any rubber hose running under floor to your carb. Sounds like might be leaking there.
Plus make sure not leaking from tank fitting. My boat is 86 when I bought it all rubber fuel lines were not good.

 

[NYBo]

Re: Air Pockets in Fuel Line - Normal?

Air in the fuel line is not caused by a leak in the tank itself. There is an air leak in the line, anywhere from the pickup tube above the fuel level to the fuel filter.

 

[airshot]

Re: Air Pockets in Fuel Line - Normal?

If the boat has been sitting for a while you may find some air pockets in the fuel line from the fuel settling, however once running and pumping fuel there should be no air pockets.

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

Might want to check and change any rubber hose running under floor to your carb. Sounds like might be leaking there.
Plus make sure not leaking from tank fitting. My boat is 86 when I bought it all rubber fuel lines were not good.

All fuel lines replaced from tank to fuel pump, and from there to carb. replaced all fittings from tank to engine. What does that leave?

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

If the boat has been sitting for a while you may find some air pockets in the fuel line from the fuel settling, however once running and pumping fuel there should be no air pockets.

That's what I figured. What is most likely place for air to enter system on the fuel out side?

 

[NYBo]

Re: Air Pockets in Fuel Line - Normal?

The fuel pickup tube in the tank.

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

In that case, have to replace the tank? Tube is welded into top of tank.

 

[airshot]

Re: Air Pockets in Fuel Line - Normal?

Are we talking a few air bubbles here and there or are we looking at a series of serious air pockets, enough that may cause the motor to run rough? A few minor air bubbles is norm from the fuel flowing in the line but serious pockets of air are another problem.

 

[Jacalore]

Re: Air Pockets in Fuel Line - Normal?

Air pockets, not bubbles. More like an inch or two in length. They move around, but don't move thru...

 

[NYBo]

Re: Air Pockets in Fuel Line - Normal?

In that case, have to replace the tank? Tube is welded into top of tank.

That would be unusual. It is usually screwed into a bung that's welded to the tank. Tempo Withdrawal Assembly - iboats Can you post a picture of the top of your tank?

By the way, keep in mind that fuel is being sucked, rather than pushed, out of the tank. Therefore, an air leak may not result is any visible leakage of fuel. There can even be an air leak where parts screw together and appear to be tight.