Glow Plug Light (1979 300SD)

[benzjag]

The glow plug light on my 79 300SD blinks until the glow plug relay cuts out. The glow plugs test good from the relay AND at the plugs themselves using my ohms meter. The light during glowing BEFORE I turn the key to start is a solid light. It's only after starting, the light blinks and will blink until the relay stops. I know some plugs are not glowing because the car "misses" for a few seconds.

Any ideas what's going in? Never had this on my W123/W126 diesels.

Thnx.

Richard

[amilio]

79' SD as well and I have the same issue sometimes. Seems to happen more when the car is cold. Tried a new relay and still have the same intermittent issue. Wondering if it's an issue with the fuse as that's the only thing I haven't replaced yet (first thing I did was replace all the plugs and ream the plug holes). Agree that the plugs are not working when it blinks. Sometimes they glow normally after waiting on the relay and trying again.

Hoping you have luck getting advice on this issue so I can fix the problem on my car as well!

[benzjag]

UPDATE!

Long story short, I had 2 glow plugs bad even though they tested good using my ohms meter at the relay AND getting a spark at each plug by running a wire from the positive terminal on the battery (to each plug)! 

In working on MB diesels for 30 years, this is the 1st time I have seen this!

I replaced all plugs. The light now does not blink (and the car runs perfectly after the light goes out)!

[amilio]

Did you test them by taking them out of the holes and seeing if they glow? Wondering if I'm having the same issue. Thank you for updating!

[benzjag]

Yes. I took the plugs "out of their holes". I used my jump box: negative cable on the body of the plug;the positive where the wire screws on. If good, the plug will instantly get hot,  glowing red on the tip.

Did you test them by taking them out of the holes and seeing if they glow? Wondering if I'm having the same issue. Thank you for updating!