Hello everyone,

Long time lurker here. Been reading and reading since I acquired my new to me 300D and have been coming short on this issue.

Car fires right up cold but seems to idle on 4 cylinders and smokes a bit like a mosquito fogger until she warms up a bit. I've done all the new to you car maintenance (fluid changes, glow plugs tested, holes reamed, glow plugs replaced). Cold dry compression test after valve adjustment came back 295, 300, 290, 290, 250. Not great numbers but not terrible. My previous W123, an 83 240d was in the 230s on all cylinders and ran great and started well in single digit temps. While I had the valve cover off I eyeballed the timing chain stretch and its looking like 3-ish degrees or so. Pulled the injectors and pop tested. Number one and number five were squirters, all five nozzles replaced and injectors all pop at about 1950-1975psi. At this point I'm thinking the compression difference between number 5 and the rest is the culprit, but I would appreciate some fresh eyes and ears on the subject. Videos below.

History on the car is thin. Previous owner was an older fellow and it was being sold for him by his son. The implication is that its been sitting relatively unused for awhile. I've been warming it up and semi-daily driving it with a 5 mile 75mph run on the highway each time. Plenty of power and smooth idle when warm. Odometer and fuel gauge are bit wonky so don't have a reliable MPG number at the moment. Working on that.

I'd like to see if this cold idle issue can get sorted out, or if its just a live with it and enjoy what you have type situation.

oh, mileage shows 156k and change, but with the sometimes working odometer who knows, but by the interior and pedal wear I'd say its still south of 200k

here are the videos:
Cold start / idle
https://www.youtube.com/watch?v=MUPAskc5EdU

Hot idle
https://www.youtube.com/watch?v=atnTQLhkfwA


Thanks everyone
Adam

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

Could be due to the lower compression in that one cylinder not combusting until the engine warms up to help it out. Before I look into that I'd also verify the injection pump timing is right. I find that with fresh injectors it makes them pop a bit late in terms of timing and advancing a degree or so can help a little. You may also have carbon stuck rings. Some members say that soaking the cylinders in Marvel Mystery Oil can free them up restoring stuck rings, but that may just be them seeing a wet compression test vs. dry. Final question is about why you wait so long after the glow plug light goes out before starting.

__________________
Garage:
1983 300TD
1985 300D
1993 190E 2.6

Social:
Metric Restoration on Instagram

Carson, Thanks for the thoughts on the topic. I was thinking the compression might be it, but its not that terrible. I have been pondering a ring soak and / or an oil change to full synthetic to see if that helped. A John Deere mechanic friend also suggested that the injection timing might be an issue. I'm hesitant to mess with it as its not something I've played with before. As for waiting past the glow light before I crank, I timed the relay at about 23 seconds so I tend to let it glow for about 15 or so to try and get things as hot at they will get before firing it off. It doesn't really help so I'm not quite sure why I still do it LOL.

Thanks again for the response

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

That seems like too long for a glow plug problem. You might crack the injector lines one at a time to figure out which cylinder isn't contributing.

Hi Adam ;

Nice car there, how cold was it when you lit it off ? .

Because it's an "old mans car" I wonder of mayhap it's just in need of some hard running .

I recently took my old 240D over the hill to fully warm it up and get the crud in the cooling system loose so I could flush it .

I was zooming up the hill on the freeway with the throttle close to pinned wondering how it wasn't slowing down when I suddenly heard a LOT if "nailing" and a LARGE CLOUD of light blue exhaust smoke came out ~ I was worried I'd damaged something and pulled over, the engine idled smoother than it has for some time now, it didn't over heat and when I took off again it ran smoother and stronger to boot .

This is a thing many have done to clean out accumulated carbon deposits ("Italian tuneup") .

I too believe in the soaking of the pistons to loosen up carbon and crud but I see your exhaust smoke clearly looks like excess fuel and by 3 minutes the engine isn't smoking and idles smoothly .


Go back and re check the valve gaps with the engine stone cold then run it hard for at least 30 minutes on the open road and see if it doesn't run better .

Looks to me like you got a deal there .

FWIW, I bought balanced injectors from Greezer and they made my old engines run noticeably smoother and with less smoke , I'd suggest taking the injectors to some place that will balance them so they all pop within 5# of each other .

I too ran an older (1978 N/A 300CD) with much lower compression than you have there and it started easily in the low 40's temperature wise and never smoked a bit , ran smooth as silk .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

resto108, Ive cracked the lines, I'm pretty certain its number 5 thats missing more often than its hitting while cold.


vwnate, Thanks for the compliment on the car. It was about 75 outside when i made that video, car had been sitting for 2 days. I also had one of those moments on one of my highway runs. heard a bit of a pop and then a cloud of smoke followed by smoother power on the road. I'm planning on rechecking the valves this weekend and have been toying with adding some snake oil to the crankcase and running it hard for 500 or 1000 miles to see where that gets me followed by an oil change to full synthetic. Other than the cold idle miss and the very occasional cold trans 2 to 3 flair the car runs pretty well, hell, eve the AC and cruise control work. I do need to replace the water pump as well, it seems to be rattling a bit, but no drips from the weep hole.

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

Sounds like you're on the right track here .

Avoid snake oil in the sump ! .

There are myriad Diesel fuel treatments , I use one on every fill up to keep the fungus at bay .

DIESEL 911 seems to work well and most truck stops have it .

I don't know who's the recommended supplier for water pumps, I bit the bullet and bought one from M-B, are you aware they have a "Classic Center" that will sell you factory M-B parts for less than your dealer ? .

I'm jealous of your cold A/C ! .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Not much new to report on this issue. Still smokes out the neighborhood and idles like crap cold, but after a short time of actual driving it clears up. Rechecked the valves this past weekend and they are all good. Did change the water pump, but now it looks like i need a new fan clutch. There is quite a bit of play in the clutch shaft, so hopefully that part shows up soon. Just slowly chugging thru these little issues.

Next little annoyance is a squeak that sounds like its coming from inside the car when I go over a bump.

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

You'll ge there, it's old and needs your love .

If you can find the time pretty much everything has been discussed here and solutions posted .

I've been attacking my 240D's ailing A/C and have learned how little I knew by following another's thread, I now have a twenty degree temp. drop between out side air and the dash vents, I also have discovered even more DPM / DPO damage and bodges deep within the dash .

Just keep at it you have a very fine car there indeed .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

This car is beginning to drive me crazy. Fired it up yesterday evening. Shut it down, went to fire it up a few minutes later and nothing, no click, no struggling starter, just nothing. sigh....

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

Not a problem , sounds like your shifter , not the end of the world for everything wears out eventually . The bushings for the shifter needs replacing , jiggle the shifter when it’s in its park position all the way forward .

Give it a start after you’ve given that a try. The engine sounds fine , just need motor mounts , trannie mount also , should quiet things down also . I found the more I drive an old Parker the better it gets , oil and trannie fluids and filters are a must , most of the time. I go for new calipers and pads also , these cars will go forever so learn the car , it will save you tons of money , this from a w123 fanatic .

Adam ;

Not a huge thing, CHECK & TEST before opening your wallet .

Quite often the shifters plastic bushings fail, you'll know because the lever wobbles in your hand .

At either end of the rod connecting the shifter and the tranny safety switch are more bushings that occasionally fail, to test for these failures reach through the steering wheel with your left hand and hold the key in the "start" position whist your right hand slowly moves the shifter from "P" through "L" and back again it's very important to move the shifter slowly as the working range of the safety interlock switch gets smaller as things get looser .

Give this a try, also test the battery to see how many volts it has at rest .

Quite often the charging system isn't -quite- up to snuff and in town short hop driving will leave the battery a little bit low .

I ass-U-me you're handy with basic hand tools, we here can walk you through this so it's a reliable easy starter without $pending your entire $avings .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanks for the pep talk guys.

The neutral safety switch was my first thought, ran it thru the gears, stopped in neutral and tried it, nothing, back in to park, nothing. I replaced the shifter bushing a few weeks back to cure a rhythmic clicking at speed that was driving me crazy.

chasinthesun - I put a new tranny mount in last week, it was a bit soft when i was under there eyeballing the center carrier and flex discs. I think there is more to the cold idle shakes than just motor mounts. It defiantly missing cold.

vwnate - I've got the tools and probably most of the ability, its patience I need LOL. this is my second 123. I never should have sold the last one but such is life...

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

Okay, you made a mistake, you won't do that again and you know pretty much what to do .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better