First thing I would like to get out of the way. I have almost 20 years experience in the distant past as a master automotive mechanic, primarily working on Japanese cars (specifically Honda/Acura) and a working knowledge of diesel theory and I have owned diesel trucks (Fords) and cars (1985 Volkswagen Jetta turbodiesel and a Peugeot) over the years, all of which I have worked on and kept maintained and running over the years. I am also working with limited cognitive functions due to years of chronic illness, this is important to understand as while I have "forgotten" much of what I once knew, I do have the ability to re-learn it and remember things. So please be understanding when I don't initially grasp something or when I take time to get a grip on something that is said.

I just got this car a couple of weeks ago and when I got it somebody had previously tried to reconfigure the fuel feed system to get it running. The primary fuel filter was missing entirely, they had taken the fuel inlet hose and routed it to the outlet on the filter housing (effectively looping the fuel) and on and on.

So I have replaced the fuel lines and configured them back to the correct routing (thanks to the Internet for finding the correct routing) but I am left with a car that still won't start and I have a few questions.

The "cigar hose". What is its function and is it critical to the proper running of the fuel system? I suspect that it is required as it is mentioned everywhere. Does it prevent air from bleeding back into the low pressure fuel system when the engine is shut off as I suspect?

The injection pump low pressure check valve: I have read a lot about this banjo bolt check valve but it has left me confused. Is the spring pressure critical? Is there any way to measure the internal pump fuel pressure (on the low pressure side) to determine if this check valve is working correctly? Is this banjo bolt check valve available again (I have read it was discontinued by MB)?

I did put in a clear fuel hose on the outlet side fuel return (back to the tank) to see if there is any air bubbles circulating back to the tank. That does not appear to be happening, but when I leave the car sitting overnight, all of the fuel drains out of this line. That indicates to me that there IS an air leak somewhere.

This one may not be related but I will mention it anyhow. It appears as though on the last time (or nearly so) the car was driven, the driver ran over a rock that smashed in the oil pan directly where the sump pickup is located, smashing the sump pickup and restricting oil flow into the pump. Hopefully there was enough oil available to lubricate the engine well enough. I have ordered a new pan & gasket and sump strainer assembly which I should get on Wednesday and install this week. My question is, might this oil restriction/starvation cause the engine to not run (outside of catastrophic engine failure- which is possible but it does have compression and it does crank over well and it almost wants to start)?

I think the fuel lines from the tank and the tank itself are OK, as I do not see air in the pre-filter at any time.

Any help is much appreciated!

Edit: Here is a picture of the old girl in her hospital bed.

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