Air in Fule Line Problem

[BobberAnn]

I am getting air in my fule line. I recently changed the fuel separator/litler with a WIX filter. Hadn't had the problem before. Can you geta bad filter? I was very careful changing out the filter which I do every year. I also changed the fule line & bulb wehn I first started having the problem. Its a 1990 115 hp Merc / pump. I am going to change the filter again and see if it fixes the problem. any other ideas?

[Mark Mc]

One thing to be aware of.....

A fuel pump can only pull so much suction. Each fuel pump has a spec on how much vacuum it can draw.

Each fuel filter has a certain amount of resistance that has to be overcome by the fuel pump. The filter also has a spec on the normal pressure drop across it (when clean).

Then you have the resistance of the fuel line (e.g. how long is it?) and possibly gravity depending on where the fuel tank is.

If the fuel pump is on the ragged edge of overcoming the resistance of the filter and line, then it will try to suck air from somewhere.

[1pump]

:yeahthat:


Your new filter may interchange by part #, and it may be identical in appearance, but it might have just a little too much restriction, especially if your fuel pump is on the lower edge of it's performance (like Marc Mc said).

I sold Wix filters for years, and the only defects I recall were the occasional oil filter missing a check valve. And that was pretty rare. I'm not saying you couldn't have gotten a bogus one. It happens.

Is your filter a spin-on? Maybe not quite tight enough? Bad gasket? New squeeze bulb on backwards? I once got a new bulb and the check valve in it failed almost immediately.
Are the bayonet fittings getting sloppy?
It shouldn't be able to suck air from anywhere if everything is working right. Another possibility could be a backflow or drainback from the motor when you shut it off. :shrug:

[fishonksm]

I too was having problems with air in the fuel line and loosing fuel prime. i traced it down to the o-rings in the motor fuel line connectors. I changed out both fittings and things are fine now. :yay:

[BobberAnn]

Thanks for the Info All!