My first winter with my 84SD I ran around all winter wondering why it wouldn't start without being plugged in below 20F. I had just done a valve adjustment and all my plugs tested fine. I couldn't figure out for the life of me why it wouldn't start. Then come spring I do my 2nd valve adjustment and realized I had adjusted them incorrectly. I thought the Exhaust and Intake valves were everyother. But it turns out they are not (more like E-I-I-E-E-I-I-E-E-I).

I don't know if this is your problem or not but if you can't find anything else wrong you may want to recheck your valve clearances.

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

When I was running mutil fuels I had that problem.I always kept some kerosene.I'd unscrew and dump fuel out of secondary filter,fill with kero.She'd fire up once kero was in injectors.

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

I had the injetors tested and they were all good.I am out $45 but at least I know that is not the problem.I am not familier with the proper starting sequence.I thought when the light goes off it is ready to start? Is that not a wait to start light? When the glow plugs stay energized for 30 seconds,wouldn't it make sense to wait 30 seconds before cranking to get more heat in the cyclinder? With Mercedes reputation,this seems like a screwy set up. I still don't know if that was my problem all allong.I am going to check my valve lash anyway just to be sure.What is the recomended service intervals for valve lash adjusments? Does this engine have a reputation for needing constant valve adjustments.I have checked valve lash on Cummins 12 valve engins about three times on different trucks and only a few valve were slightly off.

When the light goes off, it's ready to start if it's brand new and the compression is over 400 psi. At 150K, it might not quite be ready to start depending on the ambient temperature, the condition of glow plugs, rings and valves.

For you, it would make sense to wait 30 seconds. Most people don't want to wait 30 seconds because they need those 30 seconds to get to the next red light. The waiting time at the red light doesn't count in the total trip time, so, getting there and waiting is mandatory.

Valves can typically go 25K before an adjustment is required.

My book says to press pedal fully to floor one time under 32 degrees then start and don't interrupt it.You may need 30 seconds.Very good starters.Under 18 degrees press pedal and hold to the floor,release pedal slowly as she fires.
Now mine I don't use cold starting from book because of added 14 psi electric fuel pump.I turn key no matter how cold she fires without pedal.

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

That is some funny stuff, but too true. Just today I was waiting to turn right at a stoplight and a truck pulled over a lane to speed past a car on the road I was turning on to in order to get around that car before it went down to one lane. I waitied a bit to make sure it was clear and pulled out. A mile up the road it opens back in to two lanes. I was the first car in the left lane at a red light. The car next to me? You guessed it, the truck that floored it to get around one car.

I thought valve adjustments were to be done at 15k intervals? I don't recall what the FSM states offhand but I had 15k intervals in my head and that is what I have been doing.

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

Yep, that's the FSM recommendation, but most of us go to 25K...........the change in 15K is usually insignificant.

Hell, some of these engines go 75K and the new buyer comes on here in wonderment because it won't start in the cold...............