W124 300d OM606 issues

[Charles Morgan]

Right, having replaced all but one of my glowplugs and reconnected them I still find no glowplug light in the instrument cluster and absolutely no sign of starting.

First things first - where is the glow plug relay so I can check the resistances of the glowplugs?

 

[grober]

Will be a black box mounted on the inner wing somewhere. May vary between RHD and LHD and be hidden below other units.
Preglow relay doubts... - Mercedes-Benz Forum

 

[Charles Morgan]

Found it, but am leaving the testing 'til tomorrow when hopefully my dodgy battery will have more than enough juice in it to provide a robust benchmark for checking.

 

[a111r]

Same symptoms as my S123 had.
With nowt to lose, I re-flowed all the joints on the module's board. Bingo!

 

[grober]

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[Charles Morgan]

Pleasingly, charging the battery has got the thing started, still rough after start up and no glowplug relay light, so more investigations to be done. However, having a car start after work done by me is always a miracle, so it's a few steps forward.

 

[Charles Morgan]

Intriguing. Multimeter showing .7 ohms on all bar 5 (not a surprise as that is sheared off) and 3, which was replaced. Cleaning 3 furiously produced a .7 ohm result, starting smoother, but still no glow plug relay light - I asssume it stays off if any glow plug is out?

 

[Charles Morgan]

First example of a wiring loom degrading on an OM606? Not a happy picture for the wiring coming out of the glow plug relay plug. The resistance on 3 is intermittent, looks in need of a clean, but must first find my cotton buds.

 

[neilrr]

Your wiring loom is fecked, isn't that affecting it?

 

[Charles Morgan]

Almost certainly!

 

[grober]

POST 1990 W124 PREGLOW SYSTEM. may differe slightly in detail but principles and pin assignments likely the same??

 

[Charles Morgan]

Firing up beautifully now, no glow plug relay light but way better than before I changed the plugs. I think the seized plug would benefit from removal and that loom is going to be re-done, it's a simple enough thing to do.