I've been troubleshooting a hard start problem. Through the course of regular maintenance, I have replaced the fuel pump, accumulator, filter, injectors, and O2 sensor. The system pressure is 5.5 bar and the lower chamber is 5.1 bar. I checked the cold start valve and it functions properly with no leaks. The EHA current and resistance as specified by the manual for all conditions was verified. Coolant temperature sensor also reads properly at cold and normal operating temperatures. Also replaced and successfully adjusted the airflow potentiometer by referring to other posts on this site. This change dramatically improved the starting problem but did not eliminate it.

I was reading in Stu Ritters "E-Class Owner's Bible" that some compensation for normal wear of the fuel distributor can be made by adjusting the lower chamber pressure using an adjustment screw on the side of the EHA. I haven't checked for the location of the screw but the pressures that Stu was calling out don't correspond to my pressures. He suggests going from 4 bar to 4.5 bar on the lower chamber. I'm already at 5.1 bar. Does this adjustment apply to my car (1990 300 SEL)? I'm looking to see if some tuning will solve my problem before I invest in a cold start valve and/or EHA.

Thanks,
Kurt