A week ago the glow plug light stopped coming on completely on my '83 240. Since then, I've had to crank the ignition for an extended period of time, for around 5-10 times until it starts. It's relatively cold nowadays and I feel like a glow plug is broken and it's taking longer to warm up?

I know it's the glow plugs that are the problem, but don't know much about glow plugs to be honest, and even less on what needs to be done.

Any help would be appreciated. Feel free to explain things to me like I'm an idiot, because I sort of am when it comes to cars. Thanks.

 

You definitely have at least one glow plug out. That along will cause the light to NOT come on properly. When you continue to crank the engine, that is what is causing the piston cylinders to get warm, not the glow plug. I wouldn't spend a lot of time cranking the engine as it could be bad for the starter. Turn it over and let it crank a couple of times and then stop. Then try again and stop. Do that and it should kick over after a little bit and it will be easy on your starter.

 

While I am not recommending buying parts there the Diesel Giant Web Site has a good pictorial on checking the Glow Plugs with a Volt/Ohm Meter (Multimeter).

If you are in the use Harbor Freight Stores sell inexpensive Digital Meters.

Replacing the Glow Plugs is mostly a matter of removing the Nut (without dropping it) that holds the wire on to it and using a 12mm Wrench to unscrew the Glow Plug.

You are supposed to clean the Carbon out of the Glow Plug Hole with a Glow Plug Reamer. However, there are other methods of cleaning out the Carbon.

 

First off you are not an idiot, as you are asking for assistance.
Could very well be a inoperative plug, However I would check the fusable link on the fender well, if like my 300. If not I may be the idiot. As others have indicated, check the resistance of each GP while still installed. Removal of the wire is necessary, and yes do not drop the nut into the black abyss. I have and could not retrive, but it showed up on the garage floor two days later.