I’m a new member and encountering a frustrating issue with my 1973 Mercedes 450SL. Over the past year of ownership, this classic vehicle has presented a series of performance problems, each seemingly addressed only to resurface. Initially, rough running was resolved with new spark plugs and a distributor cap. Performance then improved, only to decline again, prompting the installation of a Pertronix electronic ignition system. This initially improved things, but the car’s performance deteriorated once more. A timing adjustment provided temporary relief, particularly when the air intake temperature (IAT) sensor was unplugged. However, after just two days, the car became completely undriveable.
Despite testing all components for resistance (IAT sensor, ECT sensor, MPC sensor) and vacuum (MPC), all readings appear to be within specification. The engine idles smoothly, suggesting basic functionality, but any attempt to apply throttle results in the engine dying, rendering the Mercedes 450 Sl 1973 undriveable.
In an attempt to diagnose the issue, I removed the distributor to inspect the fuel injection trigger points. These are protected by clear plastic covers. I cleaned them with Deoxit contact cleaner and dried them with compressed air. Since reinstalling the distributor, the car now runs even worse. It idles briefly but dies within seconds, or stalls immediately upon throttle application. It’s possible I’ve inadvertently disrupted the timing during reinstallation.
My primary question revolves around the fuel injection trigger points. If the Mercedes 450 SL 1973 idles on all eight cylinders, does this indicate that the trigger points are functioning correctly, and that I should focus my diagnostic efforts elsewhere? A local specialist has suggested a potential fault within the main “run” circuits of the ECU. While replacing components might eventually resolve the issue, this approach is financially unsustainable and lacks a systematic, diagnostic approach.
Located in Western Canada with limited access to specialized expertise in vintage Mercedes-Benz vehicles, I am reaching out to this community for assistance. Can anyone offer guidance or suggestions to help diagnose the underlying problem preventing my Mercedes 450 SL 1973 from running correctly? Any help would be greatly appreciated.
Thank you,
Jeff L.
