Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
That may be your problem. It would be easy enough to replace. If you don't know what the fuel pressure is at, you might want to take off the vacuum hose at the fuel pressure regulator and see if there is any raw fuel in it. That would be an indication that it's bad.
Here are the instructions on it along with a picture of where it is.
Component Identification, Shown on engine 104