Recently I noticed glow plug light not on anymore. still starts, but with dropping temps here in GA, it DEFINITELY stumbles until warm.

I have the 3 pdf's from MB that say how to test all the electrical stuff.

Rather than go through all that (cuz I suspect its a faulty GB - its got 248k on em!) is there a quick and dirty way to see if the plugs are getting hot?

Can I just touch the threaded end to see if they are warm, or will they get to a billion C at the exposed end ? Dont wana burn!

I guess I could pull all 6 plugs out and go key on to see if they all glow. Replace one that doesnt. Except getting the plugs out looks like a pain, intake prob has to come out.

Any help here would be much appreciated!

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Paul
Benz-less
I need an SDL !

dont touch the plugs at all.. they get very very hot... check the fuse a small crack can cause the glow system to not work

Good to know!

Any idea where exactly the fuse is located? I thought it was within the timer relay box, but the manuals have this tendancy to ZOOM in on the item and give vague instructions on where it actually is.

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Paul
Benz-less
I need an SDL !

i know where it is in the W123's... but an easy way to find it maybe is to just follow the glow plug wires to where they go... my wires originate from a box then to the fuse then to the plugs etc..

ahh good idea.

ill give it a try.

while Ive got an expert online, any way to easily remove the GP's? Or does the intake mani definitely need to come out 1st?

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Paul
Benz-less
I need an SDL !

I am not sure if the W124's are set up like this, but I bet they are. Check the GP strip fuse, they fail all the time.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I've got the same problem with my 87 300D. How do I check the ohm reading for each glow plug at the relay? I've found the relay and I have a good volt meter. . . While the intake manifold is off, is there anything that I should replace in addition to the glow plugs? Also, I see there are two filters for the intake manifold. Do I need both of them and how do I make sure they are OEM?

1) Remove the large connector from the relay. Set your meter to read ohms. Put one lead to ground (intake manifold will work) and the other lead to one female pin at a time in the connector, check all 6. The readings should be all the same, and under 10 ohms each (remember, there's resistance in the wires, etc so you likely won't see the 0.6 ohms you'd get from a new plug tested on the bench.) Anything that's much higher is probably a bad plug.

2) While the manifold is off, replace all the injector line clips shown in the photo above. I'd also replace the 80A strip fuse in the glow plug relay. These get brittle over time and can fail at the most inconvenient moment. I keep a spare in the fuse box as well.

3) Filters? You mean gaskets? They don't have to be OE but all the OEM gaskets I've seen are plain paper, and the OE gaskets are metal reinforced. I prefer the OE (which you'd have to get from a dealership).

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g1: 3.3
g2: 2.85
g3: 2.21
g4: 2.24
g5: 2.24
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Replace glow plugs?

Number six is bad. The other 5 are ok for now. Problem is, usually they all start failing around the same time. I'd replace all 6, used Bosch or Beru plugs, not Monark or Autolite.