I have seen so many gas engined Mercedes with the original fuel filter and fuel pump check valves, I thought I should bring this to the attention of those of you who drive them. Many models from the early 1970's up the the mid 1990's use check valves at the fuel pump. These hold pressure in the system while the car sits idle. If the pressure leaks off overnight, it may take a lot of cranking in the morning to get the engine started.
Problem & Solution
Common among these chassis:
I just replaced those items on a 1989 190E 2.6 with 130,000 miles and they definitely look like the original factory parts. Symptoms can include poor power, stumbling during acceleration, and hard starting - especially when the car has been parked overnight. If you don't have any records that these items have been changed in the past 10 years then you should replace them. The parts are not expensive and I include installation instructions.