Mercedes Benz repair: Mercedes fuel pump trouble, fuel pressure regulator, fuel pump relay

Question
QUESTION: Recently l had the fuel pump of my mercedes benz C180, 2002 model changed. When the fuel gauge gets to just less than half it ceases to pump. I have changed pumps but the problem persists. Someone has told me that certain adjustments or modifications have to be done to ensure it pumps till the tank is dry. Please help.

ANSWER: check the fuel pump relay passenger side black box google it jump wire to pins 87 and 30 you should hear the fuel pump kick on try that when the fuel is under half and se what happens

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QUESTION: The pump responds like you said but someone the engine keeps cranking until more fuel has been added. Could the scavenge pump circuit have something to do with this, which might neccesitate fuel tank removal?

Answer
was this a new fuel pump ?? Sounds like the pump in itself or a fuel problem in general have you replaced the cold staert valve or the accumulator? those are main culprits for a car not starting when it is cold the pump goes to acculator then filter then fuel pressure regulator then cold start valve all other from regulator is pumped back into return line.So with that being said your pump is working but it is not firing your engine check your airflow sensor plate and cracked hoses mainly by your intake.