96 W210 E300D OM606 air leak in fuel lines!!

[whitedemon96]

First post here and need some help!! I have a 1996 E300D that i call the white demon (car is white and is demon possessed, lol). I love the car, however, i cannot keep it running long enough to even use it anymore. I've had the car to 2 different shops with no luck and now i am diagnosing the problems myself. I have air in the fuel lines that is causing the car to die when taking off from a stop sign or red light. After the car is running it's fine, but when taking off under a load it dies the same as if you turned the ignition off and then does not want to start back (air lock at that point maybe). here is what I have done so far.....

Checked K40 relay, all looks good (no cracks and looks to be newer unit)

SOV clicking on and off with ignition switch


Replaced.....

Pre-heater gasket

Line #1 Pre-heater to Pre-filter

Line #2 Pre-filter to SOV

Line #3 SOV to lift pump

Line #4 Lift pump to fuel filter

Line #5 Fuel filter to IP

Pre-filter and Pre-filter O-ring driven all the way down and flush flat against filter base( cannot go down any tighter).

Fuel Filter and new O-ring

To start, I have replaced the o ring on pre-heater along with gasket. This cleared up the bubbles from heater to pre-filter, but on line # 2 coming out of the bottom of the pre-filter, I had TONS of air bubbles. I then got on Pelican parts and ordered all new lines (1-5), pre-filter, and fuel filter. Did not see a reason to change lines 6-8 because they are so far down the line from where the air leaks are occurring I do not think they are a problem. Changed them all out and cleaned up the leak areas of fuel. I now have MORE air bubbles than before with absolutely no detectable fuel leaks at all. How on earth is this system continually sucking in TONS of air with all new parts and o-rings? I now have air back in all 5 of the above mentioned lines and before, i just had air in line # 2. The rubber fuel line feeding the pre-heater looks good. Had a little fuel on it at the lowest point, but I believe that was from one of the leaking clear lines. Largest concentration of air is coming from #2 line. Has anyone ever had to replace the filter base from a crack allowing air to enter into pre-filter and go through # 2 line? I have also bypassed the #1 pre-heater line. I removed it and took #2 line from pre-filter outlet and put it into the pre-heater outlet. The result was then TONS of air bubbles coming from the pre-heater into the SOV. I put the #1 line back on and it's has just a few small bubbles here and there. I have used grease around all o-rings to see if there is a small air leak and there is no difference when using grease or just o ring by itself. This is why I HATE working on Mercedes Benz cars, one step forward is always 3 steps back Any ideas? What is causing the air in Line #2? If I can stop that air leak i believe the whole rest of the system will clear up. Thanks everyone!

Josh