Mercedes-Benz 420SEL engine turns over but will not start on Mercedes-Benz 420SEL

Submitted by silkey · Jun 23, 2025
Published by RepairPal

Problem overview

Some Mercedes-Benz 420SEL owners report experiencing issues with their engine turning over but not starting, often due to several potential factors. These include problems with the starter motor or relay, which may manifest as a clicking sound or complete silence when the key is turned. Additionally, a dead or weak battery is frequently cited as a common cause, prompting the need for regular voltage tests and checks for corrosion. Owners also report ignition system issues, such as faulty ignition wires or problems with the distributor cap and rotor, which can hinder starting. Furthermore, some experience difficulties related to the fuel system, including faulty fuel pumps that may prevent the car from starting, particularly in colder conditions. Lastly, sensor malfunctions that fail to signal the ignition control module can lead to a lack of spark, compounding the starting issues. It is advisable for owners to systematically check these areas to effectively diagnose and resolve the problem.

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