1983 300D W123
Cold starts: it wants to idle around 500, that's too low and it dies.
No problem starting, just doesn't want to keep running.
Current solution is to give a little throttle (under 1000 rpm) for a couple minutes until it doesn't want to die.
Is there an idle speed adjustment somewhere? (I don't have a manual.)
Thanks!

--Ed

Check your pre-filter and tank screen. When they plug, the idle suffers.

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'83 240D with 617.952 and 2.88
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Oil Burner Kartel #35

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Check adjustment of the rack damper pin/spring thing whatever it's called. I had the same problem as you describe and damper pin/spring thing was in too far. Now the car idles fine cold.

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Where can I find this rack damper adjustment?

How high does it idle when it's warm?

on the end of the inj pump right up next to the oil filter housing. It has a lock nut on it. I think you should have the engine fully warmed up before you adjust. You cant really mess anything up.

Do the 300's have that flat knob under the dash cluster for minor idle adjustments with weather? My 240 has one...maybe he just needs to tweak it a little?

Nope, no idle knob. If the 300 is running/tuned properly it doesn't need any idle adjustment to keep going when cold. Its most likely the rack damper pin as was mentioned earlier. My car had a big issue with that for quite a while till I found out how to adjust it, ran like a new car after I tuned it just right. I can crank it at 10F now without even touching the pedal and it will catch and start/run without extra throttle. Below 10F I usually give it half pedal to start it and then let off to just a little extra throttle for about 20-30 seconds so it can make some heat to keep going, it will usually keep going regardless but it starts easier when doing that and also keeps it from shuddering and shivering at first.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
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'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

When the simple things have been eliminated and if problem remains. Another source of this kind of thing can be late injector timing. this of course can and does happen with an older car that has aquired some chain stretch over the years. A car that cold starts hard or does ot stay running cold might have late injection timing. If nothing else correct injection timing does seem to aid cold starting and initial running. Just one more reason to check your injection pump timing once in a blue moon. Just my opinion.

Change your glow plugs, that's usually the problem source for cold start probs.

My '84 300SD has been misbehaving slightly as of late... Now that the temps are getting down into the 40s and 50s, my car starts at about 500 or 550 and stays there for a minute or two until it starts warming up. It doesn't die on cold starts - yet - but it does sometimes shake for like 5 seconds initially during the first morning start only.

I recently replaced the rack-damper bolt and adjusted it so that it's just far enough in to get past the engine shakes (on fully warmed-up engine, after some driving). For some reason, even with the new rack-damper bolt, this doesn't leave much more than about a millimeter between the bolt head and the locknut...

Anyhow, with rack-damper bolt properly adjusted, are fuel filters and glow plugs most likely suspects?

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84 300SD - bought in April '06 with 237,000 mi

Mine behaves the same way. Seems like a common problem. BTW. My glow plugs are all 1 year old and test out fine. The holes were all reamed out when they were replaced as well. I believe my timing is a few degrees late and I might have the rack bolt in a tad too far. I'll be correcting these sometime this week and report back.

I can't help but wonder if part of it is an old engine that might not reach its full compression until it heats up and tolerances change. Just a theory.

__________________
Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

Diesel dudes,
The rack damper in the end of the pump is just a damper for shaking type problems. Idle adjustment is a stop screw on the left side of the injection pump. You may need a "crow's foot" wrench to loosen the adjustment. Careful as some folks have snapped off the boss holding the stop screw.
dpk