Hey so having a weird issue that I need help with the mb so it normally starts with no issues but yesterday after parking at the store and coming out 5 minutes later the car started and after one second the rpm started dropping then shut off within another second and wouldn't start/run for several hours if checked all fuses they're fine. Also im getting fuel I can here the pumps running. It would crank but wouldn't start then after getting my cables to jump start cuz blood were 11.9v prior to starting. But I tried to start it once last time and it immediately started with no issues and seems fine now but I don't want to get stranded again. I'm not sure if maybe it's a faulty relay and not sure how to check them.
Please help me open to everyone's thoughts.
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moved to W164 forum...

 

it could be crankshaft position sensor...

 

Thanks I appreciate it, I'll test the old one and since I'll have it out I'll just replace it considering it's probably the original. Thanks again for your help I'll post once I get the part in and installed.