I have noticed a potential problem with my glow plugs but am not sure what it is:

1) When engine is cold, wait for glow plug lamp (a little bit,) start car, starts right up.
2) When engine is warm, wait for glow plug lamp (goes out quick,) start car, has trouble but starts after several cranks.
3) When engine is warm, wait for glow plug lamp, wait about 5 seconds more, start car, starts right up just like when it is cold.

So is the timer having issues or are my glow plugs getting old and taking longer to heat up - I am not sure if they are stock or not but the car has about 240K on it.

Any thoughts would be much appreciated. The plugs don't seem expensive but I hear a couple are knucklebusters to get out.

Thanks

 

Year and model?

 

1991 300D 2.5L TD - sorry about that - thought I had a signature with that info and apparently not.

 

99% of the time when there is an issue with the Glow Plug Light it turns out to be a Glow Plug problem.

If your car has the Pencil Type Glow Plugs go to the Diesel Giant Web Site and there is a pictorial on how to check the Glow Pugs with an Ohm Meter. However, this is not an endosement to buy parts from him.

A better check is to actually pull the glow plugs and check to see that the tips glow well; not the entire body of the Glow Plug but the tip.
When the Glow Plugs are out the Carbon deposit should be Reamed or otherwise cleaned out of each of the Glow Plug holes.
There is a Glow Plug Reamer tool made for this or you can be inventive and clean the holes someother way.

I recently had the above problem. All of my Glow Plugs looked good when checked with the Ohm Meter. When I pulled them and tested them on a Battery; on one the complete length of the Tip glowed (not good) and another Plug glow OK at the Tip (at first) but then died completely (after that I would not pass the Ohm test either).
This was with Monark Glow Plugs that had been in about 2 years. Autolite Glow Plugs are the worst Monarks are next to worst but I had bought them before I knew that. I replaced all with Bosch and my Glow plug Light is now working normal.