A truck and trailer thread.

[McMXi]

They do glow red. Put 12v to one of the ones you pulled. They run off a single relay so they all get the same juice. The relays are known to fail so if trouble starting comes your way diagnose that first. I think it’s on the passenger side of the engine bay.

The DP-Tuner programmer indicated that two of the glow plugs were bad and that was more than a few years ago. Since the IDM failed it got me to finally address the glow plug issue. I've got everything back together and all is good with no codes showing up yet.

You're right about the relay. It's on top of the engine and more towards the passenger side.

I bought a top side creeper a few years ago and that thing is essential when working on these big trucks. So much easier to get access to the back of the engine.