Should I change these GP's?
 

My car (98 W210) began to have a lumpy start so I checked the GP's at the relay. All showed .6-.8 ohm except one which was infinite. No CEL's so far. A week later, starting seems to be worse and now I have a CEL and the GP light stays on. Had one plug on hand so I changed the known bad one. Tested the others at the GP and 4 showed .8-1.1 ohm. One showed .6. After starting the car I still have the CEL and the Glow light is still staying on. Are the readings high enough to warrant changing the other plugs? Will the CEL reset on its own or will I have to reset it?

Answer:
 

YES.
Sounds like you have at least two dead ones.
You must have a glow plug reamer for this job.








Have a great day.

be sure to thoroughly inspect the engine wiring harness, i have seen many diesels just as gas models that have seriously deteriorated wiring harnesses. that problem has also been known to turn on the glow plug light as well. as for the reamer, i have seen a drill bit used on this model aswell with good results. one issue i have seen is the plugs can break off during removal or become very stuck and hard to remove. if they break off, the head will have to come off.

I have a reamer and I used it when I changed the plug. I am aware of the sticking problems fortunately this one came out easily. I also put anti seize on the new one.

What would be the cutoff in ohms? Anything above .8? I read on Dieselgiants site in his glow plug "how to" that 1.0 or below is OK.

Anyone know if the CEL will reset? I now have both the CEL and the glow light on again.

The CEL will reset. Not sure why you have the glow plug light still on. I think the resistance readings look ok. I would check them and the connections once more. Seems like you have a bad plug, still, unless the car starts normally, in which case it seems the glow plugs are fine. On my car when a single plug fails the starting event is significantly rougher, and when two fail it is really rough. I have noticed when I change a bad plug, it is usually a pair of bad plugs, not a single bad plug.

Good luck, Jim

I'll find out in the morning if starting has improved. Starting today was pretty rough, for this car anyway. I'll report back with results.

If all the GP's are good, the GP coil light will go out. The CEL/service warning will end after 3 warm ups to operating temp from cold cycles.

Apparently bad GP's are contagious. Car started better than day before but still one missing. Rechecked GP Ohms and found the one next to the one I replaced now shows 8 ohms. So again, off with the intake. New plugs arrive UPS this afternoon. I should be able to replace and button it up before dark. I'll report again tomorrow morn. Thanks for the guidance so far.

Just change the lot of them then,