OM617 W123 being naughty when cold
 

So i have a 1983 300d that i have made other thread about various other issues.

Not sure on the mileage of the car. Says 244k, but the odometer doesn't work half the time.

No known maintenance history whatsoever

Pertaining to the engine- here is what i have done

Fuel filters (twice)
Diesel purge
Valve adjustment (three times)
Rebuilt all 5 injectors w/ monark nozzles
New return lines
(1) new glow plug
(1) new prechamber (old one took a glow plug to the face, destroyed injector and prechamber
New injector following this incident^

So.. after replacing the prechamber, injector, and glow plug on that one cylinder, The car runs x10 better than it has in my short (almost) year of ownership. Much much much more power (im guessing it was on 4 cylinders before :) ), very smooth acceleration, very smooth idle around 800-1000 RPM, no strange noises or misfires like before (see some of my previous threads), and no smoke... but only when warm.

When cold, the car shakes and misses, idles rough, and sometimes smokes a tiny bit. This lasts for maybe... 1-3 minutes or so? Then it is fine. It's only when i let it sit in the 20-40 degree weather overnight, or longer. Cranking during the day after it's been started earlier, it's golden. Strong smooth start up.

On another note, the transmission acts weird when cold as well. When i first get going, it starts to "buck" and slip if you will, around 3k rpm. Again, only when cold, and this only last for about 0.25-0.5 miles. Basically by the time i get to the end of my street its acting better. Once warmed up, the transmission acts great, minus what i think is a vacuum issue. I have lots of vacuum leaks, and my 2-3 shift is occasionally way too early depending on throttle input. Im waiting on a new trans filter and gasket to arrive so i can change the fluid- maybe that will help with the issues i'm having when cold? i'm leaking fluid from around the gasket i believe, so i do have to keep it topped off. it does this when cold regardless of fluid level.

Is this just the nature of the beast? Am i overreacting? Before this, i have only owned 2003+ gasoline chevy pick up trucks, a 2001 chevy impala, and a 2010 E63. So im used to computer controlled smooth cold starts. I've never owned a vehicle older than 2001, so bear with me.

Maybe i should replace the other four glow plugs?


Thanks

Daniel

My transmission on my 300D acted like that. I believe it's designed like that to help it get up to operating temperature faster. For what it's worth, my 380SL bucks like that when cold as well even in southern california.

Does your glow plug light turn on? If you have dead glow plugs, this won't illuminate which will definitely cause the problems you're describing. If it's illuminating, then you've done all of the basics.

I would do a compression test on each cylinder next and see what your numbers are. If I recall correctly, you might be able to increase the numbers by soaking the cylinder in marvel mystery oil. Others can chime in on this procedure.

I used to regularly start my 300D which had 300k+ miles on it regularly in central new york winters. The temp would easily hit 10-15* F . The engine always ran rough for about 15 seconds but would figure itself out in no time.

One thing that I think helped me was using 5w40 diesel oil in the winter. Would run it from Thanksgiving to about mid march and then switch to 15w40 for the summer months. Probably placebo, but worth a shot.

Assuming everything else is functioning correctly, give the lighter oil a shot.

Dead glow plugs will definitely cause the issues you're seeing. How's your compression? Once the cylinder is warm enough for the fuel to vaporize sufficiently, the smoking, skipping, and knocking goes away.

It's relatively normal for the transmission to hang in 1st longer than usual and to shift a bit firm for the first couple minutes in the cold. There's a vacuum circuit with a switchover valve in the later cars that's supposed to soften that behavior up until the engine warms up. Running synthetic transmission fluid seems to help a LOT in mine. Consider Valvoline Max-Life when you do the fluid/filter change (make sure to drain the T/C). A little extra money, but it does make the gearbox more civilized.

Regarding the naughty when cold I would consider in the following order:

1) Glow Plugs

2) Battery

3) Engine condition and compression

Dkr.

Agreed,

Place glow plugs and put a brand new battery in.

Assuming the engine is cranking strongly, why the heck would you change the battery? As soon as the starter is engaged, the glow plugs are shut off and there's nothing electronic to affect ANYTHING pertaining to the running of the engine.

ok maybe not battery - but glow plugs 100% with his reference to cold weather issues and only changing one glow plug.

"When cold, the car shakes and misses, idles rough, and sometimes smokes a tiny bit. This lasts for maybe... 1-3 minutes or so? Then it is fine. It's only when i let it sit in the 20-40 degree weather overnight, or longer. Cranking during the day after it's been started earlier, it's golden. Strong smooth start up."

as the timing chain wears it retards the injection timing. one of the symptoms of excessively retarded timing is white smoke that smells like fuel and missing at idle when cold.

Someone say there was a naughty car?
http://www.awdirect.com/product_imag...le-gloves0.jpg

Some of it is just "normal diesel". Not sure that even computer controls could help, but certainly the finer sprays in newer "common-rail" diesels should help cold running. If a few glow plugs are out, it will definitely make it run rougher when cold. In my 300D's, I recall that at least 2 glow plugs must be bad before you even get the "no lamp" dash indication. Why not test them with a multimeter, since that takes ~2 min (test at GP relay connector). My 1984 was very rough cold when my son left it a few months ago. I found 1 glow plug open and changing it helped a lot. After driving 1 mile at 35 mph on a cold morning, my engines both idle fairly smooth. BTW, there are posts & youtubes which show cheap glow-plugs which test ohms OK but don't work right since they glow in the middle instead of at the tip. A lot of discussion on which glow plugs are best or at least not total crap. I started tracking which brands I have replaced. So far failed: Bosch (perhaps OK since installed when bought) and CP something (Chinese, <20K miles), and no VSP failed yet (at ~20K miles). Some say Autolite aren't good. But all this is low-number statistics.

For what it's worth, my glow plug light on my 85 300D went out with only 1 dead plug.

OP, this guide can help you figure out which plug is exactly bad:

Mercedes Diesel Glow Plug Repair

I miss you guys and the om617 :(

Thanks for all the replies everyone. Honestly have never been on another forum and have this much assistance this quickly

So I think im going to replace the glow plugs and go from there. They heat up slower than my 240d I just bought that has been sitting for 14 years and was in a flood.

I've honestly never done a compression test on it, I need to.

Trans filter+gasket will be in Thursday, so changing fluid then.

I will report back when I get it worked out

Fix your odometer
 

How can you brag about how many miles you have on your Mercedes if the ODOMETER IS BROKEN???

Even better.

Odometer says 244k, but tell them it stopped working before i was born.

No but really, next time i have the cluster out im fixing it. i would like to keep track of my mileage. It works sometimes. I've put "1,500" miles on car since i purchased it last year, but i would guess that number is more like 3,500.

Dirty/plugged prechambers? The other 4 that haven’t been replaced due to the injector/prechamber meltdown on the one you did change? Was that a pic of your brand new monarch injector nozzle that melted? Maybe once the engine is warm the crud in them prechambers loosens up and clears the prechamber holes? Once cold that crud gets hard and idles rough until they are warm and loosen up to clear holes again? If you have changed out a prechamber then you must have the tools and ability to remove the other ones to clean them? I soaked mine in a bucket of solvent. They were fairly gummed up with carbon,etc. Came out looking brand new. I had to use new prechamber crush washers when those prechambers were reinstalled. Maybe you can soak them still in the engine ( injectors removed). I’m sorry if this has been mentioned, I’m getting confused jumping around threads, and different cars. curious as to why that injector looks like that, wow! It would be a shame to have to replace the rest. Sounds like you have been burning some less than ideal diesel? I would wonder what kind of byproduct is being left behind after it is burnt. I couldn’t find the response to that one valve you couldn’t properly adjust? Also can’t find if you got those new nozzles pop tested? Again, sorry if I am confusing threads/cars. I hope you get it sorted out and running well. It sounds like you are getting there. Good job!