How much fuel in fuel filter?

[longhike]

How full should a fuel filter be? My guess was that it should be full since it’s mounted in a vertical position, and it seems like my guessing is wrong.

It works but why isn’t gravity filling this up? (I know it’s a stupid question but I’m not smart enough to know that I shouldn’t ask it )

 

[ILENGINE]

Because the remaining space is actually gas vapor. And the filter acts like an expansion chamber for the fuel. And the filter media acts like a wick.

 

[longhike]

Thanks!

 

[sgkent]

Had a 1971 VW bus with those style filters in the 70's and early 80's. Went 700,000 miles in it, and they never once were full of fuel. Somehow air or vapor is always present.

 

[bertsmobile1]

If you cut it in 1/2 lengthways you will see the outlet has an internal tube that is 1/2 way down the filter
So when it fills you get an air pocket that can not be evacuated
If you fit it the other way round it will fill to the top but the crud will be on the inside of the paper element so you can not see it .
On mowers I service regularly I some times do this because it seems to worry people .
When installed flat the bubble will be a little smaller