howto set fuel injection unit for W123 230E mercedes benz

W123 with 115 engine using CIS does require CO meter for proper adjustment. North American version vehicles typically have catalyst installed, so be sure mixture is not too rich (excessive unburned fuel will damage catalyst). Depending on service performed, maintenance versus fuel distributor replacement, adjustment should not require more than 1/2-turn movement for original fuel distributor. When setting mixture initially, for example when fuel distributor has been replaced, it is perilous to attempt adjustment without CO meter. While it can be done without CO meter (set mixture screw very lean; attempt to start engine; open adjustment 1/4-turn at a time; keep attempting to start engine; get car to idle; touch up adjustment after test drives), the longevity of catalyst may be affected and maximum performance through fine tuning will take significant time to achieve. Mixture too lean will cause higher combustion temperatures and possibly pre-ignition (pinging), too rich will dilute oil, increase fuel consumption (poor fuel mileage results) and create carbon buildup. Never have I had to move CIS adjustment screw more than 3/4 turn, which includes cases of rebuilt head(s), exchanged camshaft(s) and relocation of vehicle to different altitude. These were all situations addressed using CO meter and other specialized diagnostic tools.