The more a fuel filter blocks up the higher the fuel level appears to be as the fuel needs more area to pass through the same volume, So half full is good and full of fuel is bad when filters is horizontal in situ.

Vertical standing filters are another thing altogether and do not indicate the level of flow as well through the filter as one mounted horizontal.

The stock early A12 fuel pump should deliver at least 1/2 liter in one minute (late A12 pumps deliver more than twice that)

Mine run about half full. Never had a problem

Fuel filter will appear low and with lots of air in it that's normal. But when the engine is turning over the fuel should look agitated like it is passing.

Not sure what pressure you require if it's for turbo maybe it's not enough to just have the mechanical pump.

Hey guys,

I'm playing with my draw through setup having problems but thats for another thread. I'm trying to eliminate some of the variables

Info: Car hasn't started or run for a long time, but has been cranked and had short moments of bad running idle.
I have noticed that the inline fuel filter isn't full, it appears to be at most half full and sometimes almost empty after periods of cranking without it then running. I thought maybe the stock mechanical pump wasn't working properly so took the line off the other side and fuel will pump into a container when cranked

Is an empty filter/low level normal? or should it always be full?