In Summary
  • Do not ignore that fault. A computer diagnosis will confirm my remote diagnosis. The glow plugs can be easily replaced by a good Mercedes technician.

Hi Paul, I recently bought a Mercedes Benz ML4matic with a 320 CDi diesel engine. I have noticed that it delays to start when I turn on the ignition and when it does, it brings a spiral amber light which stays on for a while before switching off. What could be the issue as I have just serviced the engine? Harriet Kansime

Hello Harriet, your Mercedes W164 320 CDi most likely has faulty glow plugs. Whenever you buy a used car diesel engine with a mileage of about 100,000 Kms (60,000 miles) always check the glow plugs.
Each cylinder has one. Your six cylinder Mercedes engine has six.

A glow plug is a heating device with a pre-heat start and post glow phase, which helps to start a diesel engine and maintain good performance.

Do not ignore that fault. A computer diagnosis will confirm my remote diagnosis. The glow plugs can be easily replaced by a good Mercedes technician.