How to find bad glow plug? How to change glow plugs.

Asked by Sep 12, 2013 at 12:44 AM about the 1968 Mercedes-Benz 220

Question type: Maintenance & Repair

2 Answers


With an ohmmeter measure from where the wire connects to the top of the plug to the engine block. A good glow plug should measure 1-3 ohms. They unscrew light a spark plug but they are much smaller in diameter. I would suggest changing them with the engine warm.

You must be referring to a later model as my glow plugs are all four wired in parallel with 2 wires connected to each plug and not grounded through the engine block,. They are about the same size as a rregular 14 mm sparkplug.

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