Mercedes Benz repair: 96 E300 fuel problem, fuel tank cap, vacuum leak

Question
below 1/2 a tank the car has a real problem starting in the cold mornings.....from full to 1/2 a tank the car will always start right up but will go through what seems like a tremendous amount of fuel until it gets close to 1/2 a tank when the fuel mileage will return to normal. In all instances once started, the car will seem to run normal. Thanks to your previous help I have sealed up the o-rings around the fuel lines going in/out the fuel filter housing, but there stillappears to be air bubbles in the fuel line (more noticible below 1/2 tank). There also does not appear to be any visable leaks under the car in the mornings...I apreciate anything you might be able to tell me....thank you....mark

Answer
When you remove the fuel tank cap, does it blow pressure out, or suck air in?

1996 Mercedes Benz E300 D
Inspect all plastic fuel lines for age cracking, yellow clouding and abrasion wear, replace as needed.  

Check under all fuel line mounting clips for signs of corrosion = micro pin hole = vacuum leak only = sucking air.

Check rubber fuel hoses from fuel tank to steel lines for signs for age cracking or ANY trace of dampness = micro pin hole = vacuum leak only = sucking air.

Clean or replace the fuel tank vent, if equipped with one.