Hi all. New handle, same neanderthal (I used to go by neanderthal but forgot my log in details. Tried to contact administrators to no avail.)

To whit.
Acquired a 1991 250TD with the NA OM602. Everything was fine until recently. Turn ignition key on, GP idiot light illuminates, turns off, turn key to start position and go. Lovely.

Lately when I turn the key to the ON position the GP idiot light doesn't illuminate. However, after starting it will then illuminate. (I understand that this is normal; depending on water jacket temperature the glow plugs may stay on with the car running for about 90 seconds. In fact, a few times, while driving, the GP light has illuminated. So, ... normal.)
I'm not sure what is causing the glow plugs to not turn on when I turn the key to the ON position, but then turn on after the engine has started. Any thoughts/ observations/ pointers would be greatly appreciated.

Also, my car was imported from Europe. It has a pre- heater (Webasto? Sorry, i'm in bed and really comfortable!) which heats the coolant, circulates it through the cooling circuit, and blows the heated air into the passenger cabin. You can even set what time you want it to go on, effectively preheating the cabin a little, for instances like when I get off work at 10PM. Or when I go to work early and don't need to go outside and turn it on in the cold. Nifty.
This system helps with starts when the engine is cold, of course. On cold mornings I go out and turn it on about 15 minutes before I need to leave and the car starts much quicker and settles into a regular idle almost immediately. If I don't then it takes longer to start the car and it takes longer for all 5 cylinders to start firing (based on the vibration.)
With the recent winter storm here in Texas i've obviously been employing this system heavily. However, I had to remove my battery and charge it after the car nearly failed to start one night after work. Since reconnecting the battery the system ... doesn't fire. I can hear it starting to make the right noises, but it doesn't make the jet engine sound that used to indicate it was on and working, and if i'm in the cabin I definitely don't feel warm air coming out the vents.

Any input on what's going on with that would be appreciated.
(I did kinda stick the battery in there quickly, it was cold and I was standing on very slippery ice! so I do need to go check and make sure an errant wire wasn't disconnected in my haste.)

Thanks.

This is not normal.

This is how the relay tells you that there is a problem.

Test the glow plugs...I'm confident you'll find one or more is bad.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Last time I had an issue like that (albeit it was on an OM617) it turned out to be the glow plug relay. A bad glow plug could potentially cause that too I suppose, but I'm putting my money on a bad relay......

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

There is a testing procedure in the FSM to pinpoint the problem - really worth reading.
As christuna said, it is indicative of problems with either glow plugs, relay or wiring.
Don't speculate - test.

Thanks for your responses.

Perhaps i'm misreading these two posts from this thread where they briefly discuss the after glow.

I don't have a FSM but I do have a Haynes manual so I guess I have more reading to do.

Even on cars with the afterglow the light is supposed to come on before starting and go off after starting

15 Engine Electrical System - M602, M603

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

That last page, the paragraph on the right, most insightful and most pertinent. Thank you.

Anyway. I bought 5 glow plugs.

How ... where ... what ... access are you supposed to have to them in order to remove them. Every bloody thing is in the way. Intake tubes. Fuel lines. Throttle linkages. Oil filter housing. Injector pump. Even the wiring harness for the glow plugs limits access to some of them.

I changed 4 of them. I'm really at a loss as to how to change that last one. I literally gave up.

Key on, no GP light. Still. Probably that 5th one that I didn't change. 30 seconds later you can hear an audible click, GP light comes on. Car started. Yay. It wasn't doing that, so that's good.

Drove it around for a bit (It's been almost three weeks since I last was able to drive it) then key off, and it kept running. Manually shut it down. So I guess I dislodged something in the vacuum system that shuts it off (it is a vacuum something or other, right?)

Also, one of the captive nuts for the glow plug wiring fell into the abyss between the injection pump and the block. Anyone have a parts number for that? I shade tree mechaniced it with a nut from Home Depot that was the wrong physical size but had the correct threads to connect to the glow plug.

Every time I touch something on this car, something else stops working.

Does the light come on after the car has started?
Yes check your vacuum lines sounds like you bumped it off. You could remove the intake Manifold to have better access for removing the GPs.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Before going through the hassle of pulling the intake try and swap out the glowplug relay on the drivers side wheel arch. Its $49 for an aftermarket part and probably due anyways due to low lead solder.

Yes, the light comes on.
I was hoping to avoid removing the intake manifold but it seems that it may be necessary.

At that price i'd buy one regardless.
I ran across something that said in the glow system it's basically 3 things, the relay, the wiring, and the glow plugs themselves, and that it's rare for the relay or harness to fail. There was a testing procedure as well but my little test box thing was having fits. I bought a new one and 5 glow plugs.

I'm glad it's starting, that's a big step. Anyway, my Quixotic quest will continue.

If the light comes on after it is running then the relay is telling you that you have a short circuit. Could be one of the glow plug connections is touching metal look carefully at each GP connection.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Today was awful. Work was just awful. I don't have the energy. I'll take a gander at it probably after the weekend.