1989 300E

Many thanks to all of you that have contributed to this thread.

This problem generally occurs after the vehicle has been sitting for 3+ hours and overnight. I have just had a fuel pressure test done and the mechanic indicated after the test that there was a slow pressure leak occuring. He rationalized that it was in the front half of the car and not the check valve by the fuel pump (the reason for this was that the check valve leak would be more rapid).

After making this determination, he then removed the one of the injectors to inspect the spray pattern. At this point, he noticed that it was spraying in an irregular patter. He also noted that the throttle body showed some minor residue on the inside. It was then concluded that since the aperture of the injectors were not closing properly, it was releasing some of the pressure from the fuel system.

Since this car had been sitting for 2 months prior to starting with very low mileage, it was suggested that the engine would be attached to a "motorvac" machine and cleaned with a combination of fuel and detergent. This would clean the injectors as well as the O2 sensor and other vital components. It was further explained to me that this may clear some of residue that may be impeding the injector from spraying properly and causing a potential vacuum leak in the fuel system.

After the process was completed, I drove the car home and did not find a significat change in performance. Secondly, after shutting the engine down and attempting to restart it again, it seemed to show the same reluctance to start. It will turn over when cranked but will not engage without depressing the pedal. It would seem that it does not have the extra kick (or infusion of gas) to allow it to start on its own.

The mechanic suggested driving the vehicle over the weekend and observind whether it would start. If this is not resolved, he suggested replacing the injectors. My thoughts are that if the cleaning did not work, would it be advisable to replace the injector since we cannot conclusively prove that they are at fault.

Thank you in advance for any additional insight that any of the members of this forum are able to offer.