Please take a minute to read this if you would and help diagnose the next step on my friends 96 E300D. The explanation is a little long but thorough as many of you like. Still seems like a fuel problem to me but at this point we would try anything. Do you think there is a chance it is the Tank screen? He is throwing allot on $$ at a never ending problem.
all opinions appreciated.................

MY Friend bought a 1996 E 300 Mercedes Diesel 6 cyl. Not turbocharged. The car is like new, with 105,000 miles. It came from an auction in Pennsylvania I think. When he test drove the car it ran like a Swiss watch. Four days later he went to drive it, and it wouldn’t start. It cranked four or five times until he felt sorry for the starter motor. Finally it started to hit on one cylinder and then two ,then four and finally on six. Then it ran like a Mercedes. It ran for three for four days and then wouldn’t start again, with out going through the same sequence. The days that it would run right were shorter when he parked the car facing up hill, than if he parked the facing downhill. He said It felt like the fuel was draining away from the engine. He had a Mercedes mechanic change the check valve by the injector pump, and put in a new fuel filter. It ran great for a week and then wouldn’t start. He then asked another mechanic who works on Mercedes and is really good at it, to see if he could find the problem. Mechanic said the fuel filter was filthy and the connection to the filter was loose. He replaced both of them. He also thought maybe the battery in the key might be weak. Battery was replaced. The car then ran great for ten days. Then it wouldn’t start. After going through the long cranking procedure , it started, and ran great at idle. The car had a miss from 1500 rpm to 3500 rpm and smoked blue fumes . It lacked accelerating power by missing., like it was running on 4 cylinders. When it finally reached 4000 rpm it quit smoking and ran smooth. He then took it to a Mercedes dealer and they said the fuel was filthy , and drained the tank and replaced the fuel filter for the third time. When he went to talk to them about their progress they said it was fixed and ready to go. He went out to drive it away. It wouldn’t start. They kept it for another week and replaced the fuel hoses both plastic and rubber to the fuel filter and replaced one of the other shot off valves. They called and said it was fixed... He went to get it and when they went to drive it out .. it wouldn’t start. They kept it another week saying it had water in the fuel line. They had it for one month now. He finally picked it up and drove it for a week and it ran great and then on day eight, it wouldn’t start. After the same routine of cranking ,it started and he took it back to the Mercedes dealer and they said they would find out what the problem was , but said they had no idea what it was. It is still at the dealer. My freind is waiting their call..

Thanks Bennett

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81' 240d 4 spd 140k on the clock