Video – How to Test Glow Plugs – Measure the Resistance (Still Fitted to the Vehicle):

How to Measure the Glow Plug Resistance without Removing from Vehicle.

Testing Glow Plugs Without Removing From Vehicle:

Can be a quick way to check if they’re OK. It doesn’t always produce accurate results though (if there’s poor contact, corrosion, etc). However, testing in place can still be a good indicator on the condition. I.e. Poor results – Remove the glow plugs from the vehicle and check / test again…

The brief description that follows, helps explain why your vehicle doesn’t start easily when cold, and why we need to test the glow plugs…

Petrol engines start with the assistance of a spark from a spark plug to ignite the fuel. Whereas diesel engines start using the compression of the fuel mixture. However, diesels don’t like starting when cold. Hence diesel engines are fitted with glow plugs that heat the air fuel mix to aid starting when cold.

If a diesel engine is running well and starts easily when the engine is warm, but won’t start when cold, (or takes ages to get it started when cold). It could be an issue with the glow plugs, the glow plug system (module, relay, or voltage supply). This video shows how to test glow plugs without a multimeter (test meter).

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More Detailed Info:

More detailed information can be found on this page: Diesel Won’t Start When Cold – How to Fix Glow Plugs: (Opens in a new window / tab)