W140 1993 300SEL not starting!
 

Hey! I've got a 1993 300SEL W140 which has suddenly failed to start. My engine is M104.990. The engine does turn over but the car doesn't start. There is fuel delivery, fuel pump humming, a pulsating current at the injectors along with a spark at the spark cables. My tachometer needles jump on their own and my cluster lights are inconsistent. Sometimes all lights appear and sometimes half of them on key position 2. The car doesn't start even if i put my gear to neutral. I would be highly grateful for any sort of help!

Check if your car has an ignition control module (ICM) mounted on the driver's side inner fender. It's about the size of a CD magazine that fit the older MB's CD players ... with 4 electrical connectors as I recall. The simplest trouble shooting method would be to temporarily install a known good ICM and see if the engine will start. The ICM's are quite expensive (around $2,500 when I bought one for a 1991 300CE) so you want to be sure that's your problem before buying a new one. You may be able to buy a used one from a salvage yard, but you won't know how long it will last. To maximize the life of the ICM it's important to maintain all the components (distributor cap, distributor rotor, ignition wires and spark plugs) of the ignition system per MB recommendations.