'83 Mercedes 300CD

[DaveMcDonald]

Hello, Need some insight into a glow plug(s) debacle. My wifes '83 300CD would not start this morning. ( I was not home) Out of frustration she kept trying to start it and it finally fired up. My first suspicion was the relay strip fuse. It was OK. Second, I swapped out the relay. Still no light coming on for glow plugs. Third, I happen to have a excellent turbo deisel on an engine stand, so I changed all the glow plugs from one engine to the other ( just to see if in fact I had a glow plug problem.) Made no difference. Is there another fuse or perhaps I'm overlooking something?? The glow plugs are getting power, confirmed with my test light., but the glow plug light does not come on. ( No its not the bulb, it starts very hard- no glow plug heating.) Any help would be appreciated. Thanks! Dave

Hi Dave,
Welcome to the forum, I'm surprised that you didn't get a response sooner, next time try being topic specific.
I know this isn't going to set well with the guys that go by the book, but it's a possible way for some guys without meter or other means of testing.
Disconnect the battery and connect the leads of your 10 amp battery charger to the battery cables. Place the charger in a place where you can see the meter of the charger while sitting in the drivers seat. Make sure that all electrical things are off. Turn the key to the position that will enregize the glow plugs and see what happens. It will clearly peg the meter on the charger. You won't know if all plugs are working but you'll at least know if the system is functioning.
Did you try a search on glow plugs yet? Im sure theres tons of info on the subject.
You didn't say what year your CD is. It will make a difference, I believe the models prior to 80 had a series glow plug circuit, and the 80's on, were parallel.
Also welcome to the informal CD club, I've had a 80 for about five years, and just bought a 83 a couple of weeks ago.
Ernie

[Ken300D]

When someone turns the ignition key to ON you should be able to hear the glow plug relay click under the hood if you are standing there.

So, you need to verify that you are getting the electrical signal to throw the relay. If not, trace that back - perhaps the ignition switch?

Ken300D