Is the engine cranking too slowly? Are we getting good crankshaft and camshaft position signals and synchronizing the injectors?Ĭheck the cranking speed, if it is less than 200 rpm diagnose the starting system: Battery, Starter, Voltage drops. Also, the Glow Module sometimes shorts out the LIN bus which is internally bridged to the alternator LIN inside the CDI module, when this happens, some bizarre electronic problems can occur including a no start condition, unplug the module to quickly check if it is causing a problem. There is an SST Fixture / Kit for extraction and drilling if necessary. Note: The Glow Module is a common failure item and the typical cause is a shorted glow plug, it is best to replace all the glow plugs as a set with the module. Run the Diagnostic Test via actuations in the Glow Module and check the fault codes, failure of the glow system can cause hard starting and no start conditions particularly in cold weather. The 642 engine uses a complex Glow system to aid starting as well. If the engine is cranking too slowly the heat from compression will dissipate before the fuel can ignite. What is it that ignites Diesel? Is it compression? It’s the heat generated by good compression. Avoid clearing the faults especially with SCR problems as this can be perceived as “tampering” and complicate repairs. Note: some faults on this engine are active even when shown in a “stored” state, and some faults can’t be cleared at all unless the vehicle is driven and a drive cycle is successful. Verify the drive authorization (immobilizer) system is allowing the engine to start. Hook the Autologic up and do a complete vehicle scan, record the scan and do not clear any faults yet. What are we missing? Use your Autologic early in the process, there is a lot of “free” information you can get with very little time and work. Think about the problem, what types of things could cause a no start on a diesel vehicle? What do diesels need to run and start? Fuel, Heat, Air, Timing. A sooty tailpipe indicates the DPF has failed. Note: grey/white smoke may indicate an injector is stuck open and spraying fuel into the exhaust but not atomizing it which is necessary for combustion. While you’re in there, feel the turbo for play, binding, or damage. Look the engine over, check the oil level, look for fuel leaks, check that the intake ducting is sealed properly and the air filters are in good condition.Does the battery look old? Is it fully charged?.Open the hood, inspect the battery cables and terminals for tightness and corrosion. Do you see blue, black, or white/grey smoke?.Have someone else crank the engine, and look at the tail pipe. Is there any noise or sign of combustion?.Does it sound like the compression is consistent?. As with any Diagnosis, we’re going to start with the basics, use our senses, and gather information.Ĭrank the engine and lListen:to the engine crank, Unfortunately, these problems rarely come with relevant DTCs. The OM642 family engine is used in many Mercedes-Benz / Daimler Chrysler vehicles including:ĭodge, Freightliner and Sprinter Trucks …ġ64 Chassis: … M元20 CDI and M元50 BlueTECġ64 Chassis: … G元20 CDI and G元50 BlueTECĬranking No Start conditions are a common concern in our experience on Mercedes vehicles with the OM642 engine, and we’ve assembled a diagnostic process to help identify the root cause.
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