Annie Best

I had huge loss of power on a up hill with my 1998 S500 but no other fuel problems

After some testing they recommend for me to replace the fuel pump and rear filter - Done, power loss sorted

Now I have a problem only on hot starts, where the car is cranking, but wont start unless I apply pressure on the throttle.

Please advice on what the problem can be, someone suggested that the non return valve is not working and the fuel seeps back into the tank.

Is this possible and how do I fix the problem

rcrc7

The NON return valve is usually built-in to the fuel pump outlet nozzle. My older W126 does have a seperate unit of NON return valve.installed into the fuel system lines.. You should be looking at all those basic stuffs such as i.e. operating fuel pressure, spark plugs and its coil , how much of the valve timing chain has deviated from the basic setting, etc, etc. ...just my 2 cent worth.