Ongoing issue with '93 2.5Turbo glow plugs...
 

My '93 300D 2.5 Turbo will not glow! Here's what I have done.

I have replaced all 5 glow plugs after using a glow plug reamer on each prechamber. I am using Bosch glow plugs.

I have replaced the ignition switch.

I have replaced the glow plug relay with the OEM Mercedes relay 007 545 9932.

I have replaced fuse# 7.

When I turn the ignition to glow, there is no light. Just for kicks I removed fuse# 7 and retried the ignition. The glow light dimly came on for about 1/2 a second. I replaced fuse# 7, retried the ignition, and no glow light.

I also have Stu Ritters E Class Bible, but he offers no advice for my situation. I did notice in his book the '93 2.5 Turbo has a different kind of glow relay with an internal fuse. He states there is a 60 second after glow after the engine is started. That doesn't help me now, but I thought it was interesting.

Are there any Technicians out there who can offer a solution?

where are you located? there may be a member nearby with experience or knowledge for tracing the problem.

Location
 

I am in Dublin, Ohio (suburb of Columbus) and my shop is in London, Ohio which is about 25 miles west of Columbus.

i'm not a tech, but how is the actual harness of wires going to the plugs? In my '92 i found two that had rubbed against either the intake or head and broken.

I agree. This is one of the model years for which Mercedes used "biodegradeable" insulation on their wires. It was supposed to be simply a less toxic form of plastic but someone didn't do their longevity tests correctly. The insulation breaks down after a few years and wires short to ground or each other. Someone recently posted a couple of photos here.

Jeremy

Must have been East German wires.

Last night after more testing, I suspect the problem is with the wiring. The hint was that I removed the glow plug harness from the glow plug relay, and turned the ignition on. The dash light came on as expected. I repluged the harness into the relay, turned the ignition on, but no dash light! Because I have already reamed and replaced all of the glow plugs (unnecessarily because they all tested fine!), I have to thing the problem is with the wiring. Because it is a "one piece" wiring harness, I will have to replace the whole thing. I feel that I am somewhat of an expert now on the 93 2.5 turbo diesel glow system!

the good is that you know the problem. The bad is that now you'll have to take the intake off to get the harness out (at least I had to in order to repair my harness). It'll be a good time to take the intake to a shop that can hot tank it.