Failed Glow plug system on 93 300D 2.5 Turbo
 

Here is my problem. My 93 300D 2.5 Turbo will not start. The glow plug indicator light on the dash does not light when turning on the ignition. I have tested each of the 5 glow plugs with a test light and they are functioning perfectly. I then replaced the glow plug relay with a brand new one ruling out that possibility. I checked the hot line going to the glow plug relay, and it (red wire 12v) is supplying power as expected. I am puzzled.

What could be preventing power from getting from the glow plug relay to the glow plugs?

Any ideas would be greatly appreciated.

Thanks,
Roy

Have you checked your fuses?

On my SD the wire that runs with glow wires to coolant sensor for the glowplug control broke in the plug.Reconnected a works. Without it the controller assumes engine is hot.

The glow relay gets power through a pink/red wire in run or start. Pin 1 in the 4-pin connector at the relay. Is there +12V at that wire when you expect it to be glowing?

Sixto
87 300D

No Glow
 

I would check the OVP relay Fuses (Behind the Battery Compartment).
I would check the Ground from the PreGlow Relayto W3.
I'd get a new fuse for position #7 in the fuse box(And clean the contacts)
'Just for Giggles,put the Gear Selector into Neutral and see if you get voltage
when you turn the key to "Glow".

Just verifying that you are getting voltage to the plugs does not mean that the plugs are energizing and heating the combustion chamber. Think of it this way - if a light bulb burned out you could test the voltage supply and it would be fine, but the bulb still would not illuminate because it was burned out. IIRC if the glow plug controller doesn't "see" resistance through 4 plugs the glow plug light will not illuminate.

The best way to check glow-plug operation is via a current draw test, the next best way is with a resistance check.

Search the archives there is plenty of specifics on checking/testing glowplugs, its about the second most popular topic (right behind favorite oil brands)