How to Replace a Duramax Glow Plug

by Bryan Cowing
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detail of diesel engine image by Petr Gnuskin from

Duramax engines are a line of diesel engines manufactured as a joint venture of General Motors and Isuzu. In a Duramax engine, glow plugs play the same role that spark plugs play in a conventional gasoline engine. Rather than produce a spark like a spark plug, however, glow plugs create heat which causes diesel fuel to combust and the diesel engine to start and run. Replacing Duramax glow plugs is very similar to replacing spark plugs.

Step 1

Locate the vehicle's power relay box. This will be a black plastic box located on the right side of the engine compartment near the wheel well.

Step 2

Open the power relay box by pressing in the tab on the lid and pulling up at the same time.

Step 3

Examine the inside lid of the power relay box. There will be a wiring diagram that shows you the proper wiring of the glow plugs to the engine.

Step 4

Examine the center of the engine compartment to find your glow plugs.

Step 5

Place the socket wrench over the entire glow plug.

Step 6

Twist your socket wrench to the left until the glow plug is loose. Do not try to remove the glow plug entirely with the socket. It is very easy to lose a glow plug in the crevices of the engine.

Step 7

Remove the glow plug with your hands once it is loose.

Step 8

Insert the new glow plug and tighten it with your socket wrench.

Step 9

Repeat these steps for the remaining glow plugs. Following the diagram on the back of your power relay box, re-wire the glow plugs.

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