[bennyfolse]

Now that the cold is finally here in Texas my 300D wont start. I figured it's the glow plugs since the light doesnt even come on at first but on second crank it comes on and goes out after only a few seconds. I pulled the glow plugs and the first 4 were varying degrees of oily and gunky while the last one was fine. So what's making them oily and will that cause them not to function?

 

[tony1963]

Fuel residue.

 

[300Dman]

What is the mileage on your Engine.

If you are burning Diesel Fuel and the Plugs are shiny and oily the Oil is coming from the Engine. Worn Piston Rings, Valve Stems/Seals/Guides.
Another possible would be the Turbo Seal on the Compressor side

With your description of the #5 Glow Plug not being Oily this does make it seem like it might be something coming into the intake manifold. Turbo leak or Blow-by from the Intake? Because where the Turbo outlet hooks up is closer to the Front end of the Engine than to the Rear.

If you are burning an alternate Fuel that is not Biodiesel than that could be the cause.

Since Winter is all most hear you might think of adjusting the Valves, checking the Camshaft Timing and Fuel Injection Pump Timing.

If the Plugs are not actually Oily (burned Oil has an oder to it) it could be your Injectors need servicing/rebuilding or you are having some issues that are related to the Fuel burning well in the Engine.

 

[BioNerd]

........."If you are burning Diesel Fuel and the Plugs are shiny and oily the Oil is coming from the Engine. Worn Piston Rings, Valve Stems/Seals/Guides. ".............

Worn Piston Rings.... overhaul engine, very expensive.

More common is to have this: (a DIY $60+ repair)

solution: https://mercedessource.com/node/678

don't forget your wave washers:https://mercedessource.com/node/7201