Mercedes B Klasse Diesel engine starting problem

Sounds frustrating Does it happen more when the engine is cold or hot Have you tried a different ignition key Maybe the immobilizer is acting up Does the starter motor turn the engine over, or does it just click If it clicks, it could be a weak battery or a bad starter If the engine turns over but doesn't start, then the ignition switch or ignition coil is a good place to start checking

Thanks for the quick response It seems to happen regardless of engine temperature I only have one ignition key When it won't start, the starter motor does turn the engine over, it just doesn't fire up I'm just trying to get a handle on how to diagnose the ignition switch itself Is there a way to test it without just replacing it

Okay, since the starter motor is turning, it probably isn't the battery or starter Testing the ignition switch without proper tools can be tricky You'd need to check for voltage at different points when the key is in different positions Honestly, with those symptoms, it's best to have a workshop take a look Could be a faulty sensor too, throwing things off Better safe than sorry, especially with a modern car

Thanks for the advice I took it to a workshop, and you were right, it was tricky They diagnosed a faulty fuse that was causing intermittent power loss to the ignition system Apparently, it's a known issue with some B-Klasses The repair cost 52€ and the car now runs perfectly