So I'm going through and changing all the filters I can find on my new-to-me '96 E300. The fuel filter includes a little baggie with two O rings in it. The O rings are different sizes, one is smaller, one is larger. Where are these two rings meant to go?

Second question, I have an apparent air leak into the fuel lines. Air bubbles are only flowing in the line that connects to the top of the pre-filter (I changed the pre-filter and also the O ring for it), and one other line that's on the back side of the housing, roughly at the bottom of the pre-filter. (Anyone have a diagram with all these fuel lines?)

Since the IP and all these fuel line parts are under the intake manifold, I assume the manifold has to come off to get to most of these? Easy procedure to remove it?

Thanks in advance! I did do a forum search but didn't find just what I was looking for.

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'98 E300 turbodiesel