Testing and replacing glowplugs on a Hyundai i30 CRDi diesel engine

This page give a short description of checking and replacing glowplugs on a diesel engine.

If you are getting white smoke on start up, particularly in cold conditions, one possible cause is faulty glowplugs. You can test them fairly easily with a multimeter, without removing them from the engine. If the plugs are working correctly, they should have a fairly low resistance (less than 10ohm) which you can measure between the engine block and the top of the glowplug.

The glowplugs aren't obvious when you first look at the engine, since they are at the back. It was a bit tricky to get a photo of them, so here's a photo that doesn't show them. They are just out of sight, where the white arrows are pointing. In this picture I've already removed the plastic cover from the top of the engine which is held by two bolts. Position of glowplugs on Hyundai i30 diesel engine

Next step is to disconnect the lead to the plugs. All four plugs are shorted together by a metal strip (pictured), held by a 10mm nut at the top of each plug. There is a lead connected to the leftmost (from front) plug which supplies the voltage to these plugs at startup. Disconnect this lead first, then the 4 nuts holding on the metal strip, and remove it. Now you can measure the resistance between the engine block and the top of each plug. Check all four, and you should be able to see if any are out of line, a failed plug will probably show a very high resistance, or no connection at all. Glowplug connector, removed

To remove the plugs, you should use a 12mm plug-socket, and will probably have to remove the heat shield behind the rightmost plugs (pictured) to allow enough clearance. Recheck any faulty ones with the multimeter before replacing. Screw in the plugs by hand to ensure that the thread is correctly seated, before tightening up with a the plug-socket. Remove this heatshield for access

Then re-attach the metal strip and connector lead using the 10mm nuts. Take care not to overtighten, or you'll snap the internals of the glowplug. If you want to see what that looks like, here's a picture. Two glowplugs, one broken apart